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7 AD-AO92 077 KANSAS UNIV/CENTER FOR RESEARCH INC LAWRENCE REMOTE --ETC FIG 17/9CIRCULARLY POLARIZED MEASUREMENTS OF RADAR BACKSCATTER FROM TER--ETC(U)JUL 80 W H STILES, F T ULABY, E A WILSON DAAK7O-78C-0121
UNCLASSIFIED CRINC/RSL-TR-393-2 ETL-O234 NL... flfIIflfflflIflIflf-mhElllEllEEEEEhmln//EllEEI-EEEEEiggI-mEl.EEEE.IHEE-EElEEIIIIEIIIIEI
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CRINC DEMOTE SENSING LABORATORY
It.Lt
IllLEtVEM ;
ETL-0134
CIRCULARLY POLARIZED MEASUREMENTSOF RADAR BACKSCATTER FROM TERRAIN
AND SNOW-COVERED TERRAIN
0
in W. H. StilesF. T. UlabyE. A. Wilson
J. C. Holtzman 0TrC
July 1980 S ELF EC
Approved for public release; distribution unlimited
Prepared for:
U. S. Army Engineer Topographic LaboratoriesL - Fort Belvoir, Virginia 22060
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* ~ '~' THE UNIVERSITY OF KANSAS CENTER FOR RESEARCH, INC.* 2291 Irving Hill Drive-Campus West
Lawrence, Kansas 66045 ii
jCI(913)RL POLARIZED MEASUREMENTS
OF RDARBACKSCATTER FROM TERRAINADSNOW-COVERED TERRAIN
Remote Sensing LaboratoryRSL Technical Report 393-2
W. H. Stiles
F. T. Ulaby
E. A. Wilson
J. C. Holtzman
Fawwaz T. Ulaby, Principal Investigator
July 1980
{Prepared for:U. S. Army Engineer Topographic Laboratories
Fort Belvoir, Virginia 22060
REMOTE SENSING LABORATORY
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DESTROY THIS REPORT WHEN NO LONGER NEEDED.DO NOT RETURN IT TO THE ORIGINATOR.
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THE CITATION IN THIS REPORT OF TRADE NAMES OF COMMERCIALLY AVAILABLEPRODUCTS DOES NOT CONSTITUTE OFFICIAL ENDORSEMENT OR APPROVAL OF THE ,USE OF SUCH PRODUCTS.
........... T .......
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SECURITY SASIICTO OFTISoGE
(4 EOR WUMNTTINPAGE BEOECMLEIGFR2. GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMBER
j ETL 34 --4~ c774. 1 .. twd Subtitle) S. TYPE OF REPORT & PERIOD COVERED
RCULARLY OLARIZED ZASUREMENTSCotatRpr(Fnl
6. PERFORMING ORG. REPORT NUMBER
FAw z AN -L-CVEE RSL Tech. Report 393-211. CONTRACT ORGRANT NUM01ER11e)
J W. H. tiles; T.Alabyj E. A./Wilson ) DAAK7,9-78-C-0l 21S. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT, TASKC
University of Kansas Center for Research, Inc. AREA AWORK UNIT NUJU3EAV Remote Sensing Laboratory - West Campus
Lawrence, KS 66044 YLI I. CONTROLLING OFFICE NAME AND ADDRESS
U. S. Army Engineer Topographic Laboratories IJli,Fort Belvoir, VA 22060 !
14. MONITORING AGENCY NAME &ADDF" .t from Controllng Office) 1S. SECURITY CLASS. (of this report)
cijT~>~~i 'f-Unclassified15s.. DECL ASSIFIC ATION/ DOWNGRADING
SCHEDULE
16. DISTRIBUTION STATEMENT (of this Report)
Approved for public release; distribution unlimited.
17. DISTRIBUTION STATEMENT (of the abstract entered In Block 20, It different from Report)
I S. SUPPLEMENTARY
NOTES
19. K EY WORDS (Cont inue on reverse side )I necessary and identity by block number)
Backscatter, Microwave Remote Sensing, Radar Remote Sensing, Circular Pola-rization, Terrain, Snowcover
TO. ABST A T (Continue on reverse side It necessary and Identify by block number)ITrhis report covers a measurement program to obtain circularly polarized
radar backscatter coefficient tvttdata along with associated ground-truthinformation on snow-covered terrain. Snow-covered grass, asphalt and ice
Iwere observed a selected frequencies from 8 to 18 GHz for angles of inci-dence between 0r(nadir) and 80* Also included are some analyses of theeffects of snowcover on the backscatter from terrain.
DD O A." 1473 EDITION OF I NOV 6 IS OSOLETE UNCL SSIFIEDS/N 102-14-601 1SESCURI-tY CLASPICATION OF TNIS PAGE (ftev bae Enteed)
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.. iJqmty CLASSIFICATION OF THIS PAGE(W'Ibu Data BatmfG
SECURITY CLASSIFICATION OF THIS PA0EItMhon Dole BEatm
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TABLE OF CONTENTS
Page
PREFACE .. ... ... ............................. . ..
LIST OF FIGURES ...... ......................... . i...
LIST OF TABLES ... ... .. .. ......................... v
1.0 INTRODUCTION ...... ... ........................ 1
2.0 ANALYSES OF THE RADAR BACKSCATTER COEFFICIENT OF TERRAIN 2
2.1 Coniferous and Deciduous Trees .... ............. 2
2.1.1 Coniferous Trees .... .. ................ 2
2.1.2 Deciduous Trees .. ...... ............... 6
2.1.3 Mixed Deciduous and Coniferous Trees ... ...... 6
2.1.4 Comparison of Deciduous and Coniferous Trees 9
2.2 Asphalt and Concrete Surfaces ..... ............. 9
2.3 Plowed and Bare Ground ...... ................. 9
3.0 RADAR BACKSCATTER COEFFICIENT OF SNOW-COVERED TERRAIN . ... 14
3.1 Ground-Truth Measurements Applicable to Snowcover . 14
3.2 Backscatter Measurements ...... ................ 20
3.2.1 Snow of Various Depths on Top of Grass .. ..... 21
3.2.2 Snow of Various Depths on Top of Roads .. ..... 33
3.2.2.1 Asphalt .... .. ................. 33
3.2.2.2 Concrete .... ................. .. 48
3.2.3 Ice and Snow ....... .................. 48
3.3 Analyses of Snowcover Effects ..... ............. 56
3.3.1 Linear and Circular Polarization BackscatterRelationship .... ... .................. 56
3.3.2 Effects of Snow on the Backscatter Responseof Grass ..... .................... ... 64
3.3.3 Effects of Snow on the Backscatter Responseof Asphalt and Concrete ............... .. 64
3.3.4 Ice and Snow ....... .................. 71
4.0 RECOMMENDATIONS ...... ....................... ... 75
REFERENCES ...... .. ............................ . 78
APPENDIX A - RADAR BACKSCATTER COEFFICIENT co DATA
APPENDIX B - RADAR SNOWPILE SCAN MEASUREMENTS
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PREFACE
The Remote Sensing Laboratory wishes to thank Mr. Jerry Patterson
of the Steamboat Resort in Steamboat Springs, Colorado and
Mr. Joe Reddick, Ranger of the Arapaho National Recreation Area for
their cooperation in arranging the usage of their facilities. The
participation and help of the following individuals in the data-acqui-
sition and processing phases is appreciated:
Dennis Anderson
Dennis Carmichael
Chip Gabel
George Eger
John Williamson
Tom Near
Dan Barbour
Craig Dobson
Mohamed Abdel-Razik
Adnan Aslam
This report was prepared under Contract No. DAAK70-78-C-0121 for the
U. S. Army Engineer Topographic Laboratories, Fort Belvoir, Virginia.
The Contract Officers Representative (COR) was Mr. Richard .e--j
DistribUt C - -A8ajjsbi-t caest-
-Av djo
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LIST OF FIGURES
Page
Figure 2-1 A comparison of the angular response of ao at16.2 GHz and 17.0 GHz for shortleaf pine atthree sites ........ .................... 4
Figure 2-2 A comparison of the angular response of ao at8.6 GHz and 10.2 GHz for shortleaf pine atSite 5 in August and November .... ........... 5
Figure 2-3 A comparison of the angular response of ao at16.2 GHz and 17.0 GHz for oak and hickoryat two sites ....... ................... 7
Figure 2-4 A comparison of the angular response of a0 at16.2 GHz and 17.0 GHz for oak and hickoryat Site 6 in August and November .... ......... 8
Figure 2-5 A comparison of the angular response of o at16.2 GHz and 17.0 GHz for oak and hickory,shortleaf pine, and mixed oak, hickory andshortleaf pine ....... .................. 10
Figure 2-6 A comparison of the angular response of ao at16.2 GHz and 17.0 GHz for dry concrete anddry asphalt ....... ................... 11
Figure 2-7 A comparison of the angular response of ao at16.2 GHz and 17.0 GHz for bare groundand plowed ground .... ................ ... 13
Figure 3-la Location of test sites for the snowcovermeasurements ..... ................... ... 15
Figure 3-lb Location of the three test sites in theSteamboat Springs, Colorado area .... ......... 16
Figure 3-ic Location of the test sites within SteamboatSprings, Colorado .... ................ ... 17
Figure 3-id Location of the lake-ice test site atShadow Mountain Lake in Colorado.. .......... ... 18
Figure 3-2 Overall view of Test Site No. 1 shown on2/14/80, deep snow over grass .... .......... 22
Figure 3-3 Angular response of o° of snow , 6 incheson grass ....... ..................... 24
Figure 3-4 Spectral response of o of snow , 6 incheson grass ....... ..................... 25
Figure 3-5 Angular response of ao of snow > 6 inches(wet) on grass ....... .................. 27
Figure 3-6 Spectral response of ao of snow , 6 inches(wet) on grass ....... .................. 28
ii
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Page
Figure 3-7 View of Test Site No. 1 on 2/25/80 after thedeep snow was cleared, leaving a traceof snow ...... .. ..................... 29
Figure 3-8 Angular response of o° of snow-traceon grass ..... .................... ... 31
Figure 3-9 Spectral response of ao of snow-traceon grass ..... .................... ... 32
Figure 3-10 View of Test Site No. 2 with deep snow on2/15/80 and after clearing and a 6-inchsnowfall on 2/22/80 .... .............. ... 34
Figure 3-11 Angular response of o° of snow > 6 incheson asphalt ...... .. ................... 36
Figure 3-12 Spectral response of o° of snow > 6 incheson asphalt ...... .. ................... 37
Figure 3-13 Angular response of co of snow6 inches on asphalt ... ............... ... 39
Figure 3-14 Spectral response of o of snow6 inches on asphalt ... ............... ... 40
Figure 3-15 Angular response of o° of snow3 inches on asphalt ... ............... ... 42
Figure 3-16 Spectral response of ao of snow3 inches on asphalt ... ............... ... 43
Figure 3-17 View of Test Site No. 3 with a traceof snow on 2/17/80 ...... ............... 44
Figure 3-18 Angular response of o° of snow-traceon asphalt ...... .. ................... 46
Figure 3-19 Spectral response of o° of snow-traceon asphalt ...... .. ................... 47
Figure 3-20 Overall view of Test Site No. 4 showingthe snow-covered lake-ice on 2/27/80 withopen water seen in the background .... ........ 49
Figure 3-21 Shadow Mountain Lake test site .... ......... 50
Figure 3-22 Angular response of o° of snow on ice ... ...... 52
Figure 3-23 Spectral response of ao of snow on ice .. ..... 53
Figure 3-24 View of the snowpile and the carobserved on 2/17/80 ... ............... ... 54
Figure 3-25 Variation in received power Pr for the scandata at 10.2 GHz, RIL polarization at threeangles of incidence: (a) 00 (nadir),(b) 100, and (c) 700 ..... ............... 55
Figure 3-26 Angular response of ao of snowpile and caron asphalt . . . 0 58
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Page
Figure 3-27 Spectral response of ao of snowpileon asphalt ....... .................... 59
Figure 3-28 Linear and circular ao comparison ondry concrete ..... ................... ... 60
Figure 3-29 Linear and circular ao0 comparison onasphalt ...... .. ..................... 61,
Figure 3-30 Linear and circular polarization a0comparison on bare grass ..... ............. 62
Figure 3-31 Comparison of data reported inReference [1] with the data obtainedfor this report .... ................. ... 63
Figure 3-32 Effects of snow on the backscatterfrom grass ...... .. .................... 65
Figure 3-33 Effects of snow on the backscatterfrom asphalt .... ............ ......... 66
Figure 3-34 Effects of snow on the linear polari-zation backscatter from asphalt .... .......... 68
Figure 3-35 Effects of snow on the linear polari-zation backscatter from concrete ........... ... 69
Figure 3-36 Backscatter from snow using linearpolarization ..... ................... ... 70
Figure 3-37 Backscatter from smooth ice for linearand circular polarization. Linearpolarization data from Onstott [8] ... ........ 72
Figure 3-38 Backscatter coefficient of a sea-icepressure-ridge from Onstott [8] ... ....... 73
Figure 3-39 Backscatter from a snowpile, a car, andan asphalt parking lot ... .............. ... 74
iv
--------------------- ~ .. tJ~*
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LIST OF TABLES
Page
TABLE 2-1 Coniferous Tree Ground Truth ..... ........... 3
TABLE 2-2 Deciduous Tree Ground Truth ..... ........... 3
TABLE 3-1 Ground-Truth Data for Snow > 6 Incheson Grass ....... ..................... 23
TABLE 3-2 Ground-Truth Data for Snow : 6 Incheson Grass ....... ..................... 26
TABLE 3-3 Ground-Truth Data for Snow-Traceon Grass ..... ..................... ... 30
TABLE 3-4 Ground-Truth Data for Snow 6 Incheson Asphalt ........ .................... 35
TABLE 3-5 Ground-Truth Data for Snow 6 Incheson Asphalt ........ .................... 38
TABLE 3-6 Ground-Truth Data for Snow3 Inches on Asphalt .................. ... 41
TABLE 3-7 Ground-Truth Data for Snow-Traceon Asphalt ... ... .. ................... 45
TABLE 3-8 Ground-Truth Data for Lake-Ice .... .......... 51
TABLE 3-9 Description of Snowpi.le: Test SiteNo. 3 .... .. ... ...................... 57
KvVT
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1.0 INTRODUCTION
This report covers the conclusion of a measurement program to
obtain circularly polarized radar backscatter coefficient (00) data
along with associated ground-truth information on terrain. A previous
report [1] documented the circular polarization response of various
types of tree-covers, road surfaces, and bare-soil targets. This
report includes analyses of the previously reported backscatter coef-
ficient data, measurements and observations on the effects of snow-
cover on the various terrain classes, and recommnendations for future
studies in this area. Section 2, although by no means detailed,
provides heuristic explanations for the different scattering coef-
ficient responses reported in (1]. This section points to the need
for more measurements and theoretical developments to provide a firmer
basis for the given explanations. In Section 3, the snow-covered-
terrain data is presented, along with discussions of the ground-truth
data and the scattering behavior of snow. The final section points
out areas of interest that are not well-understood and recommnends
experimental arnd theoretical programs designed to improve the under-
standing of the circularly polarized return from terrain and to remove
some of the ambiguities observed in the data.
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2.0 ANALYSES OF THE RADAR BACKSCATTER COEFFICIENT OF TERRAIN
In the initial phase of this program, measurements were taken
on various types of terrain. The targets studied included coniferous
and deciduous trees, asphalt and concrete surfaces, and plowed and
bare.ground. Data were acquired at six frequencies in the 8-18 GHz
range using RR, RI, and LL circular polarization and at incidence
angles from 0' to 800.
This section will provi4de a brief review and interpretation of
these terrain measurements. For more detailed information, refer to
Wilson, et al. [1].
2.1 Coniferous and Deciduous Trees
All tree measurements for this program were taken at six sites
in the Mark Twain National Forest located in southern Missouri. The
sites were visited in August and in November.
2.1.1 Coniferous Trees
The type ,of coniferous tree studied was shortleaf pine. Data were
acquired at three sites. Relevant ground truth is summnarized in Table 2-1.Figure 2-1 compares the angular response of the three sites in August.
For incidence angles less than 300, Site 1, the densest, exhibits a
higher return. Note also, however, that Sites 2 and 5 differ signifi-
cantly in density, height, and circumference, yet their response is nearly
identical. It is possible that the return from the densest site is domni-
nated by the vegetation, even at low angles of incidence, while at the
other two sites a significant ground-return is present, below 300. One
might argue that this ground-return at lower angles should result in a"peak" near vertical incidence. It must be recognized, however, that the
observed response is strongly dependent on the "roughness" of the forest
floor, which is covered with deadwood, various other types of vegetation,
and fallen leaves. Another possible explanation is that Site 1 is so dense
that the upper part of the canopy almost forms a surface. Figure 2-2 com-
pares the angular respo'nse at Site 5 in August versus November. Considering
the limits of system accuracy and precision, it appears that coniferous
trees exhibit negligible seasonal change.
2
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TABLE 2-1Coniferous Tree Ground Truth
Heightto Average Trunk Tree Soil
Height Branches Circumference Density Moisture NeedleSite Date (mn) (in) (in) (100 m? 0-2c)Mitr
1 AUG 7.5 2.5 0.33 80 22% 68%2 AUG 10.4 4.3 0.58 60 22% 66%5 AUG 3.5 0.6 0.30 30 16% 65%5 NOV 3.5 0.6 0.30 30 23% 63%
TABLE 2-2
Deciduous Tree Ground Truth
Heightto Average Trunk Tree Soil
Height Branches Circumference Density Moisture LeafSite Date (in) (mn) (in) (100 m') (0-2 cm) Moisture
3 AUG 6.5 3.2 0.89 30 26% 59%6 AUG 6.0 0.6 0.39 35 12% 55%3 NOV 6.5 3.2 0.89 30 29% --6 NOV 6.0 0.6 0.38 35 29% -
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2.1.2 Deciduous Trees
The type of deciduous trees studied was a mix of oak and hickory.
Data were acquired "with leaves" at two sites in August and "without
leaves" at the same two sites in November. Relevant ground truth is
summnarized in Table 2-2. Figure 2-3 compares the angular response of
the two sites in August. The plots reveal a rather wide spread in
level between the two sites at all angles of incidence. The density
of trees per unit area and the average tree height were about the same
for both sites, but the tree "volumes" were quite different.' The can-
opy volume (branches) for Site 6 extended from 0.6 m above the ground
to the top of the canopy while the canopy of Site 3 had essentially
no branches in the lower three meters. Consequently, it is conceivable
that the greater range of volume scatterers in Site 6 is responsible
for the higher values of 00. It is possible also that the cause may
be due to some other geometrical difference between the trees of the
two canopies. In order to resolve such questions and to improve the
understanding of the mechanisms responsible for the backscatter from
tree canopies,. it is necessary to conduct measurements with a high-
resolution system capable of measuring the backscatter contribution as
a function of range into the canopy. This recommendation is discussed
4 in more detail in Section 4.Figure 2-4 compares the response at Site 6 in August versus Novem-
ber. At the higher angles of incidence, the defoliation has resultedin a reduction in level of approximately 4-5 dB; at the lower angles of
incidence, the moist November soil has apparently caused the level to
rise above that of the August data.
2.1.3 Mixed Deciduous and Coniferous Trees
An area of mixed oak, hickory and shortleaf pine also was studiedduring this experimental program. Although it was not possible to
determine the exact percentage of each type of tree, the site appearedto be approximately 60%-70% deciduous. The response of this site was
similar to that of Site 6 which was totally deciduous.
6
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2.1.4 Comparison of Deciduous and Coniferous Trees
Figure 2-5 compares the response of coniferous, deciduous, and
mixed stands of trees. Over most of the angular range investigated,
the response of the coniferous-tree site is approximately 5 dB
below that of the other two sites.
This comparison is based upon August data; a similar comparison
for November data would show little difference in level among thetree-types, except near nadir where apparently there is a significantground-return associated with the defoliated deciduous trees.
2.2 Asphalt and Concrete Surfaces
Measurements on asphalt and concrete surfaces were conducted at
Johnson County Industrial Airport near Olathe, Kansas. Both surfaces
were measured under wet and dry conditions. In general, one would
expect that the addition of water to an asphalt or concrete surface
should have two effects: (1) the average dielectric constant should
increase and (2) the water should tend to 'smooth" the surface. Theangular respon ?se of ao for wet and dry concrete, however, showed
little difference between the two conditions; the same was true for
asphalt, except at nadir where the wet surface gave approximately a5 dB greater return than the dry surface. These measurements suggest
that there was little effect due to changes in dielectric constant,especially on concrete. The 5 dB increase at nadir on asphalt maybe due to a "smoothing" effect, but quite likely it reflects the
difficulty of making precise measurements at nadir on a smooth sur-
face where a slight angular error causes a significant drop in thelarge coherent component of the return. Comparison of dry concrete
versus dry asphalt indicates that the asphalt is slightly rougher,
as expected from physical observation (Figure 2-6); comparison of
the two surfaces when wet shows little difference in roughness.
2.3 Plowed and Bare Ground
Measurements on plowed and bare ground were conducted north of
Lawrence, Kansas. As with other surfaces, the return should be a
9
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function of (1) the surface dielectric constant, which is governed
primarily by the soil moisture, and (2) the surface roughness.
During the period of time that the two sites were available for
observation, the soil moisture varied over a rather narrow range, so
the effect of dielectric-constant changes was minimal. There was,
however, a dramatic difference in surface roughness between the two
sites on both a micro- and macro-scale; this difference in roughness
is quite evident from the backscatter data such as that presented in
Figure 2-7.
12
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3.0 RADAR BACKSCATTER COEFFICIENT OF SNOW-COVERED TERRAIN
These additional measurements were conducted by the University of
Kansas Center for Research, Inc., Remote Sensing Laboratory, using the
MAS 8-18/35 microwave scatterometer system which was described in detail
in the previous report [1]. The system specifications, precision and
calibration methods were identical for this program and therefore will
not be repeated. Briefly, however, the systems cover six frequencies
between 8 and 18 GHz, operate in three circular polarization states
(RR, RL, LL) and can observe angles of incidence from 0* (nadir) to 800.
Data were acquired on three groups of terrain classes with snow
cover: (1) Grass, (2) Road Surfaces, and (3) Snow and Ice. Four test
sites were examined in the measurements. All sites were located in
the Colorado mountains; the locations are illustrated in Figure 3-1a.
Figures 3-lb, c and d give the test-site locations at a larger scale.
Test Site No. 1 was a short-grass (hay) field. Test Sites Nos. 2 and 3
were asphalt and Test Site No. 4 was an ice- and snow-covered lake.
More detailed descriptions are given in later sections. The radar
backscatter coefficient data are given in Appendices A and B.
3.1 Ground-Truth Measurements Applicable to Snow Cover
The choice of the ground-truth parameters measured is determined by
the significance that parameter is expected to play in the wave-target
interaction mechanism and by the time and manpower restrictions associated
with the data acquisition. The snow measurements were obtained at each
site from a snow-pit dug down to ground level. Photographs of these areas
are shown in several of the ground-truth tables. These pits allow access
to the snow in order to obtain snow samples and to observe the layering
of the snow. The following snow parameters were measured:
1. Depth
2. Stratification
3. Density
4. Water Equivalent
14
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Test Sites 2 i:::ia . aal ' _ : .N sL-motps 1 25 & 3 64i'ta$aaaa a
~Ia~ ; 'FT ~ ~ ::.wt,* -'~~~ Tes SiteIN 'S ,5
,aTest Sitea~aa It .P5 "I N. 0
0j w a'-Zh 31gaa~ *aa..sia--a..aaa -~ ad a P ~IaaalaI ~ % 5'a-k
a~ta-A. C.,. ~ ~ - * a-*Ctfl *3a NAT -' --a'to"01ba t~m Na-a.
Aaa 13 an. aaa 3.aaa-ta,. -. 7 c, &v ~ ____taaala~~~~~~la.0 -.i-r -aCaISt2aCaa n aa
4laa.-. 2,a,,* Saia 'a I Faa 51
Lad.t. Z C.~aana
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STEAMBOAT SPRINGS-COLORADO
LN
TETEST SITE #3
170
TEST SITE #2--"-... -..
Figure 3-1c Location of the Test Sites within Steamboat Springs,Col orado.
17
-
Nationali Partk
/ HILL.PN
ATOP
Shadow Mount
PAS Test Site #4
NRA HDQRS ZROCKY MOD
PINE T
BEACHSAdow MIn
GREEN RDGE 4
'.Oanal NATIONAL
4 nCUTT ROAT
Columbine
~~. ~ bO~t Granby Pumiping ( "'41 Ranbow P lant & Intake N
Tih IL IAER Guland,/~ ~ayElephantl Jisland % ~
- Harvey
Irnb' landr;
< Rocky P. j, .
Dam i
?fh hf 8 ' UINETTE q IV Twin Pines Point
Figure 3-id Location of the Lake-Ice Test Site at ShadowMountain Lake in Colorado.
18
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5. Wetness
6. Temperature
7. Grain Size
8. Surface Roughness Photograph
Detailed explanations of technique and procedure on the above
measurements may be found in another report [2].
The depth (d) and stratification were determined with a meter stick.
Two techniques were used to enhance the layer boundaries for their deter-
mination. Visual observations found most layer boundaries. However, for
slight gradations in density, this technique was augmented by sliding a
plastic card vertically through the snow and feeling the resistance to
its motion at the layer boundaries. The snow density (P) was determined
for each layer by taking a known volume of snow and finding its weight.
The water equivalent (W) of snow is defined as the depth of water that
would be obtained from the complete melt of a column of snow. The relation-
ship between depth, density, and water equivalent is given by
W =snow d cm
Pwater
where pwater is approximately unity, therefore
W = Psnow d cm
The snow wetness or percent liquid water within the snowpack is
by far the most difficult snow parameter to measure. The most accurate
method developed thus far is the freezing calorimeter. Calorimetric
techniques have been employed for many years by physicists and
chemists. The method was adapted to field-use by Leaf [3]. The basis
for operation is to have a known volume of solvent with known heat
capacity in an insulating container (thermos bottle) with provisions for
measuring temperature. The solvent used was a silicone compound which
remains in the liquid state at -40C, which is its initial temperature.
Ifa known weight of wet snow is then added and the solution is allowed
to reach an equilibrium temperature, then by knowing the weights of sol-
vent and wet snow, the initial and final temperatures within the calori-
meter, and the latent heat of fusion of water, the liquid water content
19
"! A
-
can be calculated. The following equation gives the liquid water content
by weight (-mw):
mw _ (Wi + E)(Tf - Ti) Csi + TfCs
100- WsLf Lf
where
Wi = weight of silicone fluid
E = calorimeter constant
Tf = final temperature of solution
Ti = initial temperature of silicone
Csi = specific heat of silicone
Cs = specific heat of ice
Lf = latent heat of fusion
Ws = weight of snow
The snow wetness by volume (mv ) is then calculated from mw and the snow
density Psnow:
mv Psnow mw
The snow temperature profile was measured with a digital thermometer
and grain sizes were determined visually. Macrostructure roughness can
be seen from roughness grid photographs. Soil moisture was measured for
the grass targets.
3.2 Backscatter Measurements
This section covers the backscatter and ground-truth data obtainedfrom snow-covered terrain.
20
- . ....
-
3.2.1 Snow of Various Depths on Top of Grass
This field (Test Site No. 1) was a very flat, 40-acre field in the
valley south of Steamboat Springs, Colorado. The location is shown in
Figure 3-lb. The grass (hay) was in its winter-dormant state and had
been cut to approximately 2.5 cm. This test site was observed under
three different snow conditions. The overall view of the test site is
given in Figure 3-2. Close-up photographs are given for each data set
in Tables 3-1 to 3-3. Snow of greater than 6-inch depth was observed
on two different days (2/14/80 and 2/16/80). Although the snow depths
were the same for each of these data sets (64 and 63 cm), the angular
and spectral responses are quite different as a result of the influence
of snow wetness (my).vFigures 3-3 and 3-4 give the angular and spectral response of 0
for a case in which the surface layer (0-5 cm) of the snow is slightly
wet (mv = 1.41%), while the interior of the snowpack is dry (mv = 0).
The dryness of the snowpack is inferred from the snow temperature pro-
file shown in Table 3-1.
Figures 3-5 and 3-6 give the angular and spectral responses to the
same snowpack under isothermal conditions. In this case, the entire
snowpack is at OC (Table 3-2) and therefore, wetness exists at all
levels. The snow wetness in the surface layer is very high at 5.2%
by volume.
The same test site also was observed with a trace of snow. These
conditions were obtained by clearing an area on the field. Figure 3-7
illustrates this area. The angular and spectral responses of o° are
given in Figures 3-8 and 3-9. The ground-truth data are given by
Table 3-3.
As a result of other constraints on the use of the MAS systems and
as a result of uncooperative weather conditions, these were the only
sets obtained over grass. Analyses of these data sets are furnished
in Section 3.3.
21
- - - -- - -
-
......... .u f. .
Figure 3-2 Overall view of Test Site No. I shown on2/14/80, deep snow over grass.
22
, I
-
DATE: 2/14/80
TIME: 1245-1535
TARGET: Grass
TYPE OF SET: Snow a 6-inch
LOCATION: Hibbert'sSteamboat Springs, COTest Site #1
Grid Size 2.4 cmWater
Layer Number Depth (cm) Density Equivalent Grain Size(From Ground) (To Layer Top) p(g/cm) W(cm) (mm)
Overall 64 -- 16.1 NA8 64 0.226 -- 0.57 59 0.214 -- 16 46.5 0.335 -- 15 35 0.414 -- 1-1.54 32 0.313 -- 1-1.53 27 0.400 -- 1-1.52 25 0.279 -- 2-31 10 0.246 -- 2-3
TARGET CONDITIONS 6Height (cm): 2.5 - _. .'
Soil Moisture (0-5 cm): 52.8% 4---by wt. 7T" , ..Temperature °C: 0.2(Ground) 2
WEATHER OBSERVATIONSoff, -z .:T jAir Temperature °C: 3.0 " -T:. .. T_Relative Humidity: 85% ---- _-,?. -
-2 ,General: -_ --- - _.
Cloudy, warm and humid - . . I-4 J
Light snow during set I __
SNOW WETNESS mv_, - -L
0-2 cm: 1.41% Air 60 40 20 0
2-5 cm: 0.65% Depth (above ground level, cm)
TABLE 3-1
23
-
0
- - >
olop a)
00
IA0
0~~0
CC
000
3: adJ
CD 0
> C C0o 0-
- CP
VD - 03-0K
cc 0 b 0
I1~ 4 .D 0
Ml C
040
(9P - U0.3.40 BIOe
24)
-
Target: Snow ?6 inches on GrassDate: 2/14/80Time: 1245 - 1535Water Equivalent (cmh 16. 1Snow Wetness m (%): 1 4
Angle of10 - I ncidence Polarization
300 RL300 RR
"- 700 RL
0 70' RR
-- 0
---- 9-- i -
-20
V)-30
-401-8 10 12 14 16 18
Frequency (GHz)j
Figure 3-4 Spectral response of' of snow >, 6 incheson grass.
-
DATE: 2/16/80
TIME: 1400-1630
TARGET: Grass
TYPE OF SET: Snow > 6-inch
LOCATION: Hibbert'sSteamboat Springs, COTest Site #1
Grid Size 2.4 cm
WaterLayer Number Depth (cm) Density Equivalent Grain Size(From Ground) (To Layer Top) p(g/cm3 ) W(cm) (mm)
Overall 63 -- 16.9 NA98 63 0.350 -- 17 57 0.214 -- 16 45 0.322 -- 1-25 35 0.408 -- 14 32 0.331 -- 1-1.53 27 0.400 -- 12 25 0.279 -- 2-31 10 0.246 -- 2-4
TARGET CONDITIONS 6Height (cm): 2.5 6 C!
Soil Moisture (0-5 cm): 52.4% 4Temperature 0C: 0.2 by wt. . , I,____
(Ground)
WEATHER OBSERVATIONS0i 0Air Temperature °C: 2.8 o
Relative Humidity: 63% CL .__ ____.
General: 1- -2
Warm, partly cloudy -4 -- - l i i i
SNOW WETNESS m i
0-5 cm: 5.2% 1
5-10 cm: 0.24% Air 60 40 20 0
10-15 cm: 1.78% Depth (above ground level, cm)
TABLE 3-2
26
-
CC
ILI0
CM 0
oe CD 0 04-
P- 0
> 0. CD0w
E L.Al CD~, * 0'
C2 m a)C" (D ~ m ta Q
ca 7 I C
10 w
0.0100
(SP) o jUG!31usr U83 uuenS
27
-
Target: Snow 26 lnches(wet) on GrassDate: 2/16/0Time: 1400 - 1630Water Equivalent (cm). 16. 9Snow Wetness m. M%: 5. 2
Angle of10 -I ncidence Polarization
- u300 RI300 RR
---- 700 RI0 700 RR
'-1
2-20
-3
01
8 10 12 14 16 18Frequency (GHz)
Figure 3-6 Spectral response of co of snow >, 6 inches(wet) on grass.
28
-
Figure 3-7 View of Test Site No. 1 on 2/25/80 after the
deep snow was cleared, leaving a trace of snow.
29
-
DATE; 2/25/80
TIME: 1730-1930
TARGET: Grass See Figure 3-7
TYPE OF SET: Snow Trace
LOCATION: Hibbert'sSteamboat Springs, COTest Site #1
WaterLayer Number Depth (cm) Densitt Equivalent Grain Size(From Ground) (To Layer Top) p(g/cm) W(cm) (nn)
Overall O-1 -- 0-1 NA987654321 0-1 -- 2-3
TARGET CONDITIONS: 6
Height (cm): 2.5 10
Soil Moisture (0-5 cm): 33.8% 4 17.
Temperature °C: 0.1 by wt. - 4(Ground) 2
WEATHER OBSERVATIONS - --L- II-
Air Temperature 'C: 0.0 =
Relative Humidity: 67% .- t TL_. .. . .
General: 41rt- 4 ltf -4-+4--... ..... .... ............. -Clear, cooling towards - -.-. --- - .... - -end of data set -4 _- - --
SNOW WETNESS my -,,
Wet but not measurable Air 60 40 20 0due to sample sizeDepth (above ground level, cm)
TABLE 3-330
-
00
L- C a
C C
0)I
0D CD C=)C
r-4 0,
I I
-0
cU 0
o IcoCD
P. 1J Cc4J/ 4
cl0
c~j a)
31
-
Target: Snow Trace on GrassDate: 2/25/80Time: 1730 - 1930Water Equivalent (cmh 0 - 1Snow Wetness m, (%): -
Angle of
10 I ncidence Polarization300 RL300 RR700 RL
0 - 700 RR
-3
a)
%0
-40o 4 0 n nA
8 10 12 14 16 18Frequency (GHz)
Figure 3-9 Spectral response of co of snow-trace on grass.
32
-
3.2.2 Snow of Various Depths on Top of Roads
3.2.2.1 Asphalt
Two asphalt areas were observed: Site No. 2 and Site No. 3
(Figure 3-1c). Test Site No. 2 was the model-airplane runway at
the Steamboat ski resort at Steamboat Springs, Colorado. This runway
is approximately 150 m in length and 15 m wide. It is unused and
normally snow-covered during the winter months. Three depths of snow
were observed at this site. Figure 3-10 shows this area before and
after it had been cleared.
When this runway was in its normal snow-covered state (before
clearing), a data-set was obtained. Figures 3-11 and 3-12 give the
angular and spectral responses of ao for wet snow (mv = 3.75%) and
an isothermal snowpack. Ground-truth data are given in Table 3-4.
Figures 3-13 and 3-14 present the angular and spectral response
of ao over 6-inch, slightly wet snow (mv = 1.0%). This snowcover was
the result of two snowfalls that occurred on consecutive days and there-
fore, a boundary was not apparent between the snowfalls. The previous
day, 2/21/80, a 3-inch layer was observed. The angular and spectral
responses of o to this very-wet-snow case (mv = 4.23%) are shown in
Figures 3-15 and 3-16. System problems were encountered during the
data set requiring an abbreviated measurement set. The ground-truth
data for these two sets are given in Tables 3-5 and 3-6.
The other asphalt area observed was the high-school parking lot
at Steamboat Springs, Colorado (Test Site No. 3). It was snowing
during the data set, but the weather was very warm and only a trace
of snow was on the parking lot. Figure 3-17 shows this area.
Figures 3-18 and 3-19 show the angular and spectral responses of 0° .
The ground-truth data are given in Table 3-7.
33
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _
-
(a)
(b)
Figure 3-10 View of Test Site No. 2 with deep snow on2/15/80 and after clearing and a 6-inchsnowfall of 2/22/80.
34
-
DATE: 2/15/80
TIME: 1315-1600
TARGET: Asphalt
TYPE OF SET: Snow > 6-inch P''
LOCATION: Model Airplane RunwayLTV ResortSteamboat Springs, COTest Site #2
WaterLayer Number Depth (cm) Density Equivalent Grain Size(From Ground) (To Layer Top) p(g/cmJ) W(cm) (mm)
Overall 5 -- 15.7 NA9876 55 0.246 --5 40 0.260 --4 34 0.280 --3 20 0.327 --2 15 0.333 --1 14 0.357 --
TARGET CONDITIONS 6
Height (cm): NA I- -
Soil Moisture (0-5 cm): NA 4--T--_ ------ ___ ! -. .Temperature *C: 0.0 rT - ..... -
(Ground) -
WEATHER OBSERVATIONS .
Air Temperature *C: 2.7 0
Relative Humidity: 86%
General: -2Warm and clear
-4 ,SNOW WETNESS my
0-5 cm : 3 .75% __" _" ___....... .... _ .5-10 cm: 0.27% Air 60 40 20 0
Depth (above ground level, cm)
TABLE 3-4
35
-
C~J 004dC
- fv ~GCD
CU
crr4-;
000(
CU
S'
f- LA< 0
(fiP aD OK CD 0Q
0.0
E 0
CD n a.L
Al (D CA. CD 0
14.-- CD
crI V
C)
Y 4 LL.
-m P--4
(SP) @0 Juspillo3o B6us
36
-
Target: Snow2>6 Inches on AsphaltDate: 2/15/80Time: 1315 - 1600Water Equivalent (cmh. 15.7Snow Wetness m. (%: 3.8
Angle of
10 Incidence Polarization300 RL300 RR
--- 700 RL
0 700 RR
0
20 -I-P
-30
(A3
-30 ..- --- -
-40 1 I I n I8 10 12 14 16 18
Frequency (GHz)
Figure 3-12 Spectral response of a° of snow 7 6 incheson asphalt.
37
.........
-
Quarter is shown
DATE: 2/22/80
TIME: 0945-1400
TARGET: Asphalt
TYPE OF SET: Snow, 6-inch
LOCATION: Model Airplane RunwayLTV ResortSteamboat Springs, COTest Site #2
WaterLayer Number Depth (cm) Density Equivalent Grain Size(From Ground) (To Layer Top) p(g/crn3) W (cm) (mmn)
Overall 14.5 -- 2.62 NA987654321 14.5 0.181 -- 0.5-1
TARGET CONDITIONS 6 ______________
Height (cm): -NA V L _Soil Moisture (0-5 cm): NA 4 T ~ ii4._Temperature *C: 0.0 - __~
(Ground) 2 ~--- -
WEATHER OBSERVATIONS ~-~7iZT ~ I~Air Temperature *C: -0.2 4.0 __ W__
Relative Humidity: 100% 7General: -2 [__ ~ __
SNOW WETNESS m _ - -
0-5 cm: i.o% ________________Air 60 40 20 0Depth (above ground level, cm)
TABLE 3-5
38
-
C.0)
a) Ia)
CD
CDC
CD 'D-4 CDI C)
(aP) 0ID JU13111003 6utj8sIe3Su
%0
'00
0C CD 00
0 00
40. 0
E 0-
C SC-5 a)
LLA-
W.0 C 09
4DP a) ZUi!s36p~-%.E 3O
-
Target: SnoN 6 inches on AsphaltDate: 2M18Time: 0905 - 1400)Water Equivalent (cmk. 2.6Snow Wetness m, (M.: L 0
Angle of10 -I ncidence Polarization
U 300 RI- ~ 300 RR-700 RI
0 700 RR
Ci~m~m -1
0
-20
-4018 10 12 14 16 18
Frequency (GHz)
Figure 3-14 Spectral response of a' of snow 6 incheson asphalt.
40
-
Quarter is shown
DATE: 2/21/80
TIME: 1430-1600
TARGET: Asphalt
TYPE OF SET: Snow: 3-inch
LOCATION: Model Airplane RunwayLTV ResortSteamboat Springs, COTest Site #2
WaterLayer Number Depth (cm) Density Equivalent Grain Size(From Ground) (To Layer Top) p(g/cmi) W(cm) (mm)
Overall 8-- 2.0 NA987654321 8 0.26 -- 0.5-1
TARGET CONDITIONS 6Height (cm): NA F - i 'Soil Moisture (0-5 cm): NA 4 _....._....__-.Temperature 0C: 2.0 I-i---I7-7--- 7.---Z-!17-- i(Ground)2 __
WEATHER OBSERVATIONS , ! _--~. o __ NOT MEASURED __ ___Air Temperature °C: 1.0 E O
Relative Humidity: 52%General:
Warm, clear . . . --4
SNOW WETNESS my_- 7LC-I 111....0-8 cm: 4.23%I' __ _ !
Air 60 40 20 0Depth (above ground level, cm)
TABLE 3-6
41
-
1* C
C) cm
OCC
C~C
C4 0-
'4-
0
-65a
LAIn
(U R4 83
C
-4c A
(ap) cp ju.9pilJJ90 6uIpe)AePS
42
-
Target: Snow 3 Inches on AsphaltDate: 2/21/80Time: 1430- 1600Water Equivalent (cm . 2.0Snow Wetness m,(%M: 4.2
Angle of10 -I ncidence Polarization
U 300 RI300 RR700 RI
0 700 RR
~0
wC0
cn-20SM1== .oo oO
-30
-401II8 10 12 14 16 18
Frequency (GHz)
Figure 3-16 Spectral response of o of snow 3 incheson asphalt.
43
-
Figure 3-17 View of Test Site No. 3 with a traceof snow on 2/17/80.
44
-
DATE: 2/17/80
TIME: 1010-1340
TARGET: Asphalt See Figure 3-17
TYPE OF SET: Snow trace
LOCATION High School Parking LotSteamboat Springs, COTest Site #3
WaterLayer Number Depth (cm) Density Equivalent Grain Size(From Ground) (To Layer Top) p(g/cm3 ) W(cm) (mam)
Overall O-1 -- 0-1 NA98
7654321 0-1 --
TARGET CONDITIONS
Height (cm): NA j - l ---Soil Moisture (0-5 cm): NA 4 i ! - 132. 'Temperature °C: 1.3 -
(Ground) 2
WEATHER OBSERVATIONS 0 ---
Air Temperature °C: 0.8 0 0Relative Humidity: 96% ; -_---
General: -2 |' ";;; -..... T T . .. .. TT TTffiLight snow during data _- - -----.------ _.--.-_- ___
seno acuulto -4
SNOW WETNESS my_
Wet but not measurable ----- H -.due to sample size Air 60 40 20 0
Depth (above ground level, cm)
TABLE 3-7
45
-
-aC
- C
C *CD
0)6 )
0) o
In
(SP) 0D IUOI:zflJa8O: 6upj~es
0
0
-0 '4-0
E 0
C CD 'I.
LJJ a) )
C" CD CDC 0
CMC
IL-Cl CD C(SP)00 U?13)Po) BUOUh
46L
-
Target: Snow Trace on AsphaltDate: 2Ail@oTime: 1010 -1340Water Equivalent (cmh. 0 -1Snow Wetness m,(%M: -
Angle of
10 -I ncidence Polarization- u300 RI- ~ 300 RR
700 RI0 -700 RR
cb
0
C -20
-30
-4018 10 12 14 16 18
Frequency (GHz)
Figure 3-19 Spectral response of co of snow-traceon asphalt.
47
-
3.2.2.2 Concrete
As a result of the uncooperative weather conditions and because
no large concrete areas were available near Steamboat Springs, Colo-
rado, the measurements of snow over concrete with circular polariza-
tion were not obtained. In lieu of these measurements, analyses in
Section 3.3 will show the levels that would be expected from snow-
covered concrete. The levels were determined from linear and cir-
cular measurements of bare (non-snow-covered) targets and from linear
polarization measurements of snow-covered concrete.
3.2.3 Ice and Snow
In this target category, two data sets were obtained.
Lake-ice was observed at Shadow Mountain Lake, located in the
Arapaho National Forest in Colorado (Figure 3-1d). The MAS system
overlooked the lake from the Green Ridge Road. Figure 3-20 shows
the overall area. The open-water area is outside the MAS observation
range as shown in the diagram of Figure 3-21. Because of the distance
to the lake from the road, it was not possible to obtain 00 (nadir)
data and the 100 data, although given, may be biased by the edge of
the shore. Figures 3-22 and 3-23 present the angular and spectral
responses of ao and the ground-truth data are given in Table 3-8.
Since the resolution cell of the MAS radar issmall with respect
to a parking lot and since both cars and snowpiles are not area-extensive
targets, the concept of a° is not really valid. Using the standard
method (for the MAS systems) of data-taking does not yield a valid result.
For this reason, a snowpile was built in the Steamboat Springs High School
parking lot (Figure 3-24) and the radar was operated in a scan mode across
the snowpile and a car.
The scans were obtained by setting the MAS system to a specific
angle, polarization and frequency combination and then moving in
azimuth across the targets and parking lot while recording the received
power. These values were converted also to radar cross-section (RCS) a.
Figures 3-25 a, b, and c give examples of the scan data for 10.2 GHz and
RL polarization at three angles of incidence: 00, 100, and 700. Received
power is plotted on the vertical axis while the horizontal axis is in
relative distance along the ground.
48
-
Figure 3-20 Overall view of Test Site No. 4 showing thesnow-covered lake-ice on 2/27/80 with openwater seen in the background.
49
-
400%
CnlG!e Ridge Road Radar Trucks
Figure 3-21 Shadow Mountafi Lake rest SI.
50
-
DATE: 2/27/80
TIME: 0900-1300
TARGET: Lake Ice
TYPE OF SET: Ice
LOCATION: Shadow Mountain DamGrand Lake, COTest Site #4
Ice thickness approximately40 cm.
WaterLayer Number Depth (cm) Density Equivalent Grain Size(From Ground) (To Layer Top) p(g/cm3) W(cm) (mm)
Overall 20 -- 5.5 NA98765432 20 .25 3.75 --1 5 .35 1.75 --
TARGET CONDITIONS
Height (cm): NA . . .... _ _
Soil Moisture (0-5 cm): NA 10' - . .-_ __ ....Temperature *C: Not Measured -- --- '
(Ice Surface) ----- - - _ ---
WEATHER OBSERVATIONS __.... _ .... . __
Air Temperature .C: 0 _ ___ ___
Relative Humidity: NotMeasured . ___ _ .... __..General:
Clear, warming throughthe data set -10 .. IN-----_-- - "_-_
SNOW WETNESS m_ - _.-
0-2 cm: 0.34%
5-10 cm: 0900 1000 1100 1200 1300
TABLE 3-8
51
-
C. C
rD co
C 0D
CD D CDJ
CMC
(SP)00 ppljj wljat0
.. w ' 4cdj~
>0
L.~4D.
E K
Ii 52
-
Target: Sngw on IceDate: V/27NTime: 0900 - 13)Water Equivalent (cm): 5.5Snow Wetness m. (): 0. 3
Angle of
10- Incidence Polarization300 RL300 RR
"-700 RL0 ---- 4 700 RR
10
S_-20 "
-30 -
-40 , ,8 10 12 14 16 18
Frequency (GHz)
Figure 3-23 Spectral response of ao of snow on ice.
53
-
Figure 3-24 View of the snowpile and the car observedon 2/17/80.
54
-
777
0C o
7~ T- C -
4-01 4-
c) I- 0 (1L* :1-
00 0
4 - 4-
4). '
(u +
LII, tU
0.11
7 _ j 0_4
po to
55
-
The results of all the scans in both relative received power and a units
are given in Appendix B.
At nadir, Figure 3-25a shows that the asphalt backscatter is higher
in level than that of the car because of the convex curvature of the
car-roof. At the higher angles of incidence (Figure 3-25b and c), the
backscatter from the smooth asphalt surface is substantially lower than
that obtained from the car or the snowpile. The Luneber Lens (LL) also was
placed along the scan-line to provide a reference radar cross-section at 30' and 70'
If the peak values of the backscatter from the car and snowpile are con-
verted to numbers using the standard calibration routine, the angular and spectral
responses may be found. Figures 3-26 and 3-27 illustrate these responses.
3.3 Analyses of Snowcover Effects
3.3.1 Linear and Circular Polarization Backscatter Relationship
The understanding of the relationship between linear and circular
polarization backscatter coefficients is valuable for several reasons.
First, it would allow usage of the much larger volume of linear
polarization data to be applied to circular polarization data bases.
Secondly, it would improve our basic understanding of the backscatter
mechanism, although this effort will require additional work.
Linear polarization data were obtained for Sandia Laboratories
[4,5] in 1978. Figures 3-28 to 3-30 illustrate the backscatter coef-
ficient data for linear and circular polarizations at two frequencies
for three targets: concrete, asphalt, and short grass. From these
curves, the indication is that for very smooth surfaces, concrete
and asphalt at 8.6 GHz, the differences between circular and linear
are small, while for the rougher surfaceS, circular is generally a
few dB below the linear data. This observation, however, will be
shown to be a minor consideration for the case of snowcover on concrete.
Figure 3-31 illustrates the repeatability for system measurements
between the first report [1] and data presented in this report. The oo
agreement is seen to be very good.
56
-
DATE: 2/17/80
TIME: 1400-1600
TARGET: Snowpile
LOCATION: High School Parking LotSteamboat Springs, COTest Site #3
The snowpile was made from wet snow. It was approximately0.9 m high and 1.2 m in diameter. For other pertinentground-truth data, see Table 3-7.
TABLE 3-9
57
-
00
I-I
EL /e ix
.a 4w 06L
CoCLA 4^
LS.-
ooo
EC%J _
P). 0O1.1iiaY UJ:e)
... 58
-
Target: Snowpile on AsphaltDate: 2/21/80Time: 1400 - 1600Water Equivalent (cm): -Snow Wetness m,(%M: 0. 3
Angle of10 -I ncidence Polarization
300 RL300 R R700 RL
0 700 R R
CO,
0
'-1
.-
0
0
0)
8 10 12 14 16 18Frequency (GHz)
Figure 3-27 Spectral response of oo of snowpile on asphalt.
59
-
*CD
(D 0
00 r
0 pu,
- 1-
0
CC
00 0
cc
U
600
-
0 00
-.a)
LA-.
C=
U' 0)
'4--
Iv CDJa
(SP C) ICDD110 5uJeeL),
CC
L- 0.
CDC
0 Un00
P.1 r-
oD CD 4
e~gen(a P). OC)lqgo6la~~
I~i r61
-
o f 00
r 3
A. 0
100
C 00
OCL
0S
ro
ad C~Cin0
CCo
__
ECD
= -Irm
CD,4< L
CD CD CD CD C
(a) P) OPjaioo uile
I6
-
30 Target: Asphalt
Frequency: 17. 0 GHzPolarization: RL
20 - 2/17/80- 8/16/79
-c= 10
,-
0
,-10
S-20
-30
-400 10 20 30 40 50 60 70 80
Angle of Incidence (Degrees)
Figure 3-31 Comparison of data reported in reference [1] with the data
obtained for this report.
63
-
3.3.2 Effects of Snow on the Backscatter Response of Grass
From the three data sets obtained on snow-covered grass, the
smoothed angular responses of ao with RL polarization are shown in
Figure 3-33 at two frequencies. These results indicate that, depending
upon snow conditions, the backscatter coefficient may be either higher
or lower than the grass in the absence of snow.
The two dominant snow parameters affecting the microwave back-
scatter properties are water equivalent and snow wetness [6,7]. The
effect of increasing snowcover (water equivalent) at angles away from
nadir is to increase the backscatter [7]. The effect of snow wetness
is to decrease the backscatter at angles away from nadir. The behavior
near nadir to changes in either water equivalent or wetness is not
as well-understood but may be dominated by the contribution from the
underlying terrain.
Observing Figure 3-32, one notes that the data obtained on 2/14/80
is on fairly dry snow, mv = 1.4% in the surface layer, while the internal
snowpack was dry. In this case, the effects of W and my appear almost0
to cancel with the o curve being slightly above the bare-grass case.
Two days later, on 2/16/80, the complete snowpack was wet and the
surface was very wet (mv = 5.2%). The o° response at angles of incidence
above 100 is seen to be much lower than the bare grass. This effect
results from the radar response being dominated by the smooth, wet
snow surface. The attenuation for snow of this wetness is very large
and therefore only the surface layers affect the o° response. If dry
snow had been observed, its o0 response would have been higher than
the curves of 2/14/80.
3.3.3 Effects of Snow on the Backscatter Response of Asphalt and Concrete
The four data-sets obtained over asphalt are illustrated in smoothed
form in Figure 3-33 at two frequencies. Again, the parameters W and mvare the dominant snow effects. These curves, in comparison with those of
Figure 3-32, seem very different; however, the differences may be explained
by reviewing the general situation of snow over terrain.
The backscatter coefficient for snow-covered terrain may have contri-
butions from both snow and the underlying terrain. The snow has two effects:
64
-
0
L- 1 )LL..
CD CD CD CD C C
>IIE=-~ IIt e
Of. /04V-.4 /-4&
4A Od r-Z/: C' %4
0A
400
0 0 0 0 0 0Ile
(gp 0 IUi~JJO3 u~apeS 00a
(9p) 0 lul:)Ijao: Bulqu-'
65U
-
CD
C)D
fL..
rLrJ
CC
I CC0
-(A
C > C ) C D D= 1C C D EC MJ - C '% j Y0
(9p) ofi 1uampJJoo 6uip:eoS 4--
00 CDC%J
N r C) Q0
CDL~ 3:
C% CCD - /'
4-
iii CD0 ' a -.LL. CLI / v.o
ooi C) 1 C)D CD CD(9P) .0 luapJaooo 6upafle:S
66
-
(1) The snow has an attenuating effect upon the radar
backscatter from the terrain, and
(2) the snow also contributes directly to the backscatter.
As a result of (1), since the backscatter coefficient for grass is greater
than that of asphalt, for equivalent conditions the backscatter from snow-
covered grass is affected more by the grass than the backscatter from
snow-covered asphalt is affected by the asphalt.
As little as W = 2.6 cm of snow on 2/22/80 is observed to raise o
significantly over the trace-of-snow case, even though there was some
snow wetness. Both of the other dates (2/15/80 and 2/21/80) on very
wet snow (4.2 and 3.8%) show similar responses for drastically dis-
similar values of W (15.7 versus 2.0 cm) indicating that the snow is
dominating the backscatter at high wetness values and therefore the
penetration depth must be less than W = 2.0 cm for these wetness levels.
The effects of snow on both asphalt and concrete on linearly
polarized backscatter coefficients have been measured previously [4,5].
Figures 3-34 and 3-35 present wet and dry snow responses along with bare
asphalt and concrete. In Figure 3-34, similar behavior to Figure 3-33
on asphalt is observed. The snow is seen to have a much greater effect
on the backscatter from the "smoother" concrete surface. When the curves
for snow on asphalt and concrete are combined in Figure 3-36, it is noted
that, for these smooth targets, the backscatter with snowcover is approxi-
mately the same regardless of the target. This fact indicates that the
snow is the dominant scatter mechanism and that for water equivalents
greater than about W = 2 cm, the backscatter from snow-covered concrete
and snow-covered asphalt is approximately the same. Similar trends also
would be expected for circularly polarized data, therefore the levels for
snow-covered asphalt given in Figure 3-33 will be comparable to the
levels that would be observed on concrete.
67 I1
-
or 0
CD a
1 1
LA..
Lr% CD4-)1D CPG; Uj00r
0 c
0e d % a) 4-
0
(U
CD 400-
Nc 0
L.
In
(9p 4.-.831OO6 IJ7
CL0 ~ ~ 68
-
co~
CDVCDJ
cL
:3i
L- C>
-~ -4-)I-OC
m 4-)
CD. -4 4.0
CI 4D I t- N
(8. adIO!1935UJf~
600
U- L
~ 00
(SP 00l.11imBlv
= - o69
-
7 00
C)
CD CD C ) D C
(9p IP 811180
.4 C~j a C4 )
coc7;Z3 0
%A
0 0 90 0 40 S.-
700
-
3.3.4 Ice and Snow
The data set over lake-ice (Figure 3-22) was taken with a 20-centi-
meter snowcover. No other circularly polarized dataare available on
snow-covered lake-ice (smooth ice), therefore, a comparison with the
HH-polarized results of Onstott [8] is shown in Figure 3-37. These
data sets on bare and snow-covered ice were obtained in the arctic.
It is observed that the levels of a of the snow-covered ice are within
about 3 dB of each other. The exact behavior of the snow-covered ice
may have been affected slightly by a low-level salinity, since thislake was close to the ocean. Noting the much lower level for the
non-snow-covered ice indicates, as for the road-like surfaces, that
the contribution of the backscatter from the snow probably is thedominant factor.
Pack-ice data, as previously stated, was not obtained. In lieu
of this data, the closest target found was a sea-ice pressure-ridge.
This ridge was 0.9 m high and consisted of 10-cm-thick blocks of ice
(Onstott [8]). Figure 3-38 presents the o data for this target.
The parking-lot data (Figure 3-26) is replotted with theaddition of the asphalt background in Figure 3-39. The values of o0
calculated for the car and the snowpile can then be compared with thelevel of the parking lot. The interpretation of this information
requires knowledge of the sensor's resolution cell and the purpose of
the measurement. If the resolution cell is large, then integrated
effects of cars, snowpiles and asphalt will be observed. Spatial
averaging of the areas of each target multiplied by their respective
oa values would then give an effective "ao" for the whole parking lot.On the other hand, if the resolution cell is small, then direct compa-
risons may be made (Figure 3-39).
71
-
hO0000
4-
N7 Z00
gL 0
U T~C~) S.a)ea
C'%JG
cf-0o 0 0 0 43
~ C'~I. 0
0000
.00 0Egt 00~ n
~~aE 4-+-e
0
/u Ir -
LL -~ CCD
(9p) ,oo IU.a!)jjgo:) 6u!ja:eOS
72
-
00
-t
00
o3 L-J
00
LA. 4-
d)
C~J0
-
-4
0
C CD
too
0 L
CD C L
en cm
(GP) p JUBl:)jjm uljqqea-
730
-
CVJ 00
LM W
(D / C/L I.N 0
L. -
cm 4= CDC
C%j r- r- CID4
(SP) ofi luGPal~ltoo BUIJ:4e3S
LflL~- L..01
000
CZ) E
I A 4-'0 = 0
-, 7 - Izz 7I
Q pnoC
LLdon 0')
(SP) oD1PP.0C UM O
74
-
4.0 RECOMMENDATIONS
Based on the experience gained from the present study, the follow-
ing recommendations are proposed:
Circular Polarization: For the few cases where the same target
was measured by the same system for linearly polarized (HH or VV) and
circularly polarized (RL) antenna configurations, the results show
that the magnitude of o° is comparable, although not exactly the same,
for all three like-polarizations. Specifically, for concrete
(Figure 3-28), the o curves corresponding to the three polarizations
essentially are indistinguishable one from the other. Although some
differences in level are apparent between o0 of the different polari-
zations for asphalt (Figure 3-29) and grass (Figure 3-30), the volume
of the data are not a sufficient volume from which to draw general
conclusions. For cross-polarization, HV and RR (or LL), there is even
less data available for comparison. Since linearly polarized data is
much more available than circularly polarized data, it may be possible
to use the available linearly polarized data bases for estimating the
circularly polarized scattering coefficient of terrain types if a pro-
cedure can be established to relate o0 (RL) and ao(RR) to ao(HH),
ao(VV) and o0(HV). To this end, a two-task program is proposed:
(a) Using surface- and volume-scattering theoretical models,
to develop relationships between the circularly polarized
scattering coefficients and their linearly polarized
counterparts.
(b) To design and conduct careful experiments to measure o°(RL),0 (RR), o°(HH), ao(VV) and co(HV) using the same system for
three classes of terrain types: (1) smooth surfaces, such
as concrete and asphalt; (2) rough surfaces, such asplowed ground; and (3) volume scattering media, such as
snow and trees.
Using the data generated under Task (b), the validity of the models
of Task (a) may be evaluated and the process, it is hoped, will lead
to the desired relationships.
75
-
T0
Backscatter from Trees: The measured ao value of a tree canopy
represents the backscattered power integrated over the effective volume
of the canopy that contributes most of the return. Thus, it is dif-
ficult to ascertain (a) the relative significance of the contributions
by the various "layers" of the canopy and (b) the degree of penetra-
tion into the canopy volume. Without this type of information, it is
difficult to formiu'late realistic theoretical models for the backscatter
from tree canopies. It is therefore recommended that careful measure-
ments be made using a high range resolution system such as a short-
pulse radar or a wide-bandwidth FM-CW radar. By increasing the modu-
lation bandwidth of the MAS 8-18 system to 4 GHz, for example, a range
resolution of the order of 15 cm may be obtained in practice (compared
to a theoretical range-resolution of 7.5 cm). A record of the spectrum
analyzer display corresponds to the power return as a function of range.
Such a record provides information on the relative backscatter by scat-
tering range layers between the treetops and the underlying soil surface,
with a range resolution of approximately 15 cm. Detailed measurements
of this type, coupled with the standard measurements of co (which employ
spatial and frequency averaging to reduce signal-fading) would lead
to a better understanding of the backscatter differences between dif-
ferent types and/or conditions of trees and to the formulation of theo-
retical models based on a more sound foundation.
Backscatter from Snow: Based on the experimental observations
made in connection with this and other investigations [5-7] of the
radar backscatter from snow-covered terrain, it may be concluded that
the three major parameters governing o° are (a) the snow water equiva-
lent (which is related to the snow density and depth), (b) snow wetness
profile and (c) the backscattering behavior of the terrain with no snow-
cover. In lieu of acquiring large volumes of data to cover a wide range
of parameters (a) and (b) for each terrain-type of interest, it is
proposed that the models developed by the University of Kansas [6,7]
(although for linear polarization configurations) be used to generate
families of o° versus e curves (at frequencies of interest) correspond-
ing to various combinations of snow depth and wetness. Such an approach
76
-
is not an exact substitute for direct measurements of o°; it is felt
that the backscatter contribution of the snow layers and the attenuation
of the underlying ground contribution by the snow layer may be estimated
with acceptable accuracy from previous measurement programs [5-7] to
provide approximate, but useful, estimates of o° for snow-covered terrain
types of interest.
77
-
REFERENCES
[1] Wilson, E. A., D. R. Brunfeldt, F. T. Ulaby and J. C. Holtzman,"Circularly Polarized Measurements of Radar Backscatterfrom Terrain," RSL Technical Report 393-1, University ofKansas Center for Research, Inc., Lawrence, Kansas,February 1980.
[2] Stiles, W. H. and F. T. Ulaby, "Microwave Remote Sensing ofSnowpacks," RSL Technical Report 340-3, University ofKansas Center for Research, Inc., Lawrence, Kansas,October 1979.
[3] Leaf, C. F., "Free Water Content of Snowpack in Subalpine Areas,"Proc. of the Western Snow Conference, 1966.
[4] Stiles, W. H. and F. T. Ulaby, "Backscatter Response of Roadsand Roadside Surfaces," RSL Technical Report 377-1,University of Kansas Center for Research, Inc., Lawrence,Kansas, July 1978.
[5] Ulaby, F. T. and W. H. Stiles, "Backscatter Response of Snow-Covered Roads and Roadside Surfaces," RSL Technical Report377-2, University of Kansas Center for Research, Inc.,Lawrence, Kansas, May 1979.
[6] Stiles, William H. and Fawwaz T. Ulaby, "The Active and PassiveMicrowave Response to Snow Parameters: 1. Wetness,"Journal of Geophysical Research, Vol. 85, No. C2,pp. 1037-1044, February 20, 1980.
[7] Ulaby, Fawwaz T. and William H. Stiles, "The Active and PassiveMicrowave Response to Snow Parameters: 2. Water Equiva-lent of Dry Snow," Journal of Geophysical Research,Vol. 80, No. C2, pp. 1045-1049, February 20, 1980.
[8] Onstott, Robert G., G. J. Dome, C. V. Delker, J. E. Pateland R. K. Moore, "Radar Backscatter Study of Sea Ice,"RSL Technical Report 331-14, University of KansasCenter for Research, Inc., Lawrence, Kansas,December 1979.
78
-
APPENDIX A
RADAR BACKSCATTER COEFFICIENT co' DATA
-
-r 0 CA CD W. to0 cn 0 - '. 0 Rr 0 0 Mo 0l r- C%j -d q* CV LC) co 0) (%i r - LA) 0) N- CA CV 0co 6 0; Oi c6 0; c6 r- 0 t.0 '6 6 c6 '0 c LA LA 4
4A/ I I I I I I I I I
L5
r_ CV) Ln LA M.. M " W'. 40, M 41t C)- CDJ
-0 r- 4D '0 m2'0 L Coj .0 LA m- to "A en0 (a -t OD m. 0o - - -a - - - - - - - -
LAto0 CV)
00- LA r- I* CO -c - WoC ON Oh% tD OD Rr
t.,- o 0N 0O r-. P- a- co W- mA LA 4*- r-j tD 0n '. CD. '.0 C C~)3CL4 0
* '. ON LA N-j N-j r o C~) cn Ln 4a lA LA -o 0" ONa 0 'aLo -.. L'a 0 - I - r W ko mr - d M - - -l -0 -~ r' -
L&o 'D N- ('a ('a - C; N- 0; C6 LA C6- C C h 0
C I g - - - - - - - - - - - -- -
o an o m co *o w m C7 aO w CD -4 a l a Y M a
LA LA Co C A -1 LA a- W- %0 0 %0 Ca CD C, -0 w' 0; 0a LA C6 CO ('a - - LA LA L 'a L6o
on r LA M- - W~ to) C) LA) 0%D' A L
L)O A- Co a Co ( N- c; 'a Co LA L A LA w-
t= LA (l) ('a LA ('O rL LA LA C) 0o - -0 'a% 00 A LA
t. O C o ('a C)'a Co(' 0% ULA r- LO Co ('a CJ LA ' LA 0 j LA D
rn - a - -r n - 0- 0 - -l Clta a9 al a al a a- ai 11 a a a* ai 9 ai 9
LD LA C- Co LA N- - %0J nLA to LA to LA CDC aL
o ( -i a- cc - -0 e N - -i w ('a -i 0 C N -i Oh *-
CA-1
-
10
CDc n -~ m. Osj CV W 4 V C 0i
C3
0 a- -
*-I..I ...
tol CJ L Z
LU.
1- 1 i CJ C cli 04. C1 c'.j eC ej eI s)
*0 0j
C-> \0o
CI- C C U 9 9 l kLU > %DP n )c
LU Cs)l O
C');
w .- c ) U I ~ C1 C. , ~ U , U
0-
-
N. C\j LO C) 0 U-) -- 00 q. C)0
C00 m l C) J9 CJ C\ C) (\a C)J C C)J C%
S.- U-) CAo~ LO r 0) CC) to co tD(.D 0 LO CJ ,-. -l ON. eJ 01 c0j (W c -cr
N. 0~ N. i 0 c0 LA N A 01iL
S-
3LA ol
cc CJ
I-ci o~~ua %D qt LA U') C)i LA LA 01 C~j -l 41- C6-4 - 0 N. LA 01 N CO LA LA C9 01 LA 9A
L- 0D
o
0Co- - " 19 LA 01 ( *) 01 C" 0 A . 09
co - ~ - - r 00 - - m -nI I I I I I I
0 I
C-j ct: 0c Ix -i LA: 0i LAixN -Ix ex I I Ix I cc Ix I I
I-,-
01 0 C~ ~ %J ~ ) ~ J CO- N
-
0 fn m2 - 7 c 0 C ! 4
(a a~ 0% '0 V - ) CO) n (w) mA 0 W0
0 4m kD t S c n m
o CW CV) N~ CV) N~ CW, NI N C)
-,A - Z
0-
CM LL LLIW a~ C\J m 0 j 4 *4- LO LO co CA - .
cc0-L m N- c N N N
2*0 00
0m
LL0 * IU.. m O LO cV) N- (w) 00 to0 C0 .4t co
NL - ~ N~ 0i N NCJ
I-!7 CD LA! C9 L9 L9 - -9-
N~ -~ m r- Na Nc CN T ON -d O
C-)
o C;- N- 00 '-: N- 00 N co
-i - -i i cc -i - e -
LD LD LD tv to
LL C6
A-4
-
CD 0 . CO '- 9OO ~ 100J 10 ('4 O r 0) 10 00 r- CV) C) PN- ' '4 (4Q ~ t C\J ('4 e, 04 C.") ('4
m-ocr 0 4 ) O o C 7
0 .co co qc CD m 0 0r C) 10) C) 0 4D h0 a 41: kL;0C~ h 0 () 0 A 1
N. j (V) - ~ cl - l -~ -l ~ 10j I-j C~~ C
C)-o 0A O U)0 o c ~
a 0-- - c- ~
..- .. .. r" c LO LdA C) -d ON -10 CO) U
0C4 :* b 0 4 L A 0 cLA -6 q; C6 10 ('4 4 0' N
-o -o C4 o ('4 - O - - ('O - -
-U- s co N.r CO Rd- LA) 00 0D .- m' -C) LO
I-- I. 0 V 7 O CJ r ~ ) O o cL) kALA (' CO; C CO LA C. 0Co~
U") 414- - -4m -o o to - co m
CO Ln ('O co Lc) to LA w. LA C- N.0 co m (o 0* %0 0 10) %Q U' N, 44
- i , -i I= - w
(Y ' C to C9 CO 1 C L
a: CU- 0
10 ~ 0' ~('4 ' 10A-5
-
CL
CCD
CDo
C 0_ _ _ _
'0
o
I-D
0 0
LL. m
5-C)
0%
~ ~ ~ ~ A-6
-
A.-A092 077 KANSA UNIV/CENTER FOR RESEARCH INC LAWRENCE REMOTE --ETC FIG 17/9
CIRCULARLY POLARIZED MEASUREMENTS OF RADAR BACKSCATTE R FROM TER-_ETC(UI
jLL AR 11 A STILES, F T ULABT. E A w ILSON DAAK7078-C1121UNCLASSIFIED CRINC/RSLTR393-2 ETLO2 3 N*2 ffffffffffff
-
o~4 mr 0D CV) C. r. '0 M A 0
00 LA at w. 0 Go r= %0 . - 01 f-scMi cM C14 C%) (w) 0i CMj CMj C C14 CM CM
.4A C\J 40 .- 4D0 %D0 LC CMi Rt CV
-c - l (' 01 '.0 19- P-'0 LA 01 0! .
oCM M C C M C14 CMj CMi C4 cM CV
o 0 CI -O
X -( 0 - CO q CM . LA C9 (C) LA C') f-0 - 60 .1: ." . ."Cj .w .nc
CM- cMi CNJ CNJ CNJ CM cMi C%J
V) A cs) CO l -01C0 0 '0 C' . e
co01 4D LA) to0 01n LA LA C0 e- LA.5- 0
0 . LA) CO %0 CD %D0 CM m' ON LA) co C 010CMi - l C M cM CM CM- - M N4 9
LI.I
LA) co 0D ci 0 CMQ LA) to0 0) CMi Go a0 CM C'9 k91 - O - CM %90
Ua. m' La) .0 '0 01 LA Os ce) co LA) W. CMi '0LaJ CMi -Oki-CM - CM CMl - cv
LaJI,, a. cY) 0 CV) 00 co CV) c mOC)
I- Id, C C') (In 4D 0 a-. '.0 LC) Rd 01ltC)CM ' L C6 4 a- 01 LA u-r_ 1 :
C% C CM M - - - CM - -
al al I, a aaa
CCDI) - Cno .9t CD Ln C 0 1 00 01 .-
On C' LLA CM 0%) C)- r-. 0D cM CM
o- --. 0- 0O C)- 0N LA r- 01 C - LA 01
- - C - CM -i - - -i -e -) cc I= 1= ix Ix a z w a
o~~~t to0 0- to- . 1 0 0 - -C; CO LA Go 01j C')-. r- 0w - CM -_ - M - CM C -
aA-
-
ON 01 l) LC) Ln f'. C.j CIj ON LA ia..
kA CV) 40 WW LA t M rl V) %. i ~OWJ CJ CJ cmJ C14 C .l vCJ VIA C*. C% J l
rr) 01 CV() Go C~j WAL
C4~ C- (% - ' C%iJ a) Cli c C>J .
0. 00 .- 01 0 C14 4NI cn O co r- W).. I W 0 O (%.J Co 0 ~ ~ 0 L l ~ C
C~u~ -4 0 LA 0
(M-01 Lf l Cl %DU- cE0 C') L A L Cli 1* 01 0 ! CO AU- CV CV) LA ct. C LA LA qd) COi 9-l 0h C'Wj LLI 00.
C-)
IJ I
Cl r. LA 0 L 0* CD 0'i to LC) 0C-C)
0
- - -i -e a-CDI I= ox ae I= ae a a
o co co
A-8
-
co _ _ 1 L) r 4DGC)
C)
aJ * 0
8n fj - - 0 0-
w_ x -- - - -m c
I-oLu . D 0 1 09. 1~ - ( o C)s
0 ~ LL 0 co I *O *O
LL.%J C) (E ~~ f c; c; C (7 Lc;r ~.~ -- - I
-o 0~ cc) ccon toan ~ Cv) C .*
I-l
0l -z .. c; C J r- C
LL o r- C~- o ~ () CJi C) OE C) 0l Li)
Il Ir I= W I I II
L)C. CD__ -
LUC c-
I-C ~ c s ~ ~ 9- 0 t Ll o 0cc * . .
I- c so ~ c .~- so c-J 's A-9v
-
I
APPENDIX B
RADAR SNOWPILE SCAN MEASUREMENTS
The scan measurements were conducted at Test Site #3. (Steamboat
Springs High School parking lot). Two scales are given for each scan.
The relative values of received power are given along with the calcu-
lations of radar cross-section a. The radar cross-section a is related
to the radar backscatter coefficient by:
a= aG Ail l
where Aill is the illuminated area.
k ______--.-----.-
-
FH 405
03
0 4
5B-
I'm-(gap
.- ..
-
-.-~rvrr"1
?!~5~.i aIJFISo~M~eA&~ ~"a" ~ -
Py.
I
~iA~ 4O~
/0 -
as
05-----
-30
C dt
I C~v- -
-10 -~5..
-IS~ ~
----------------------------------------------------------
_
-- I
- B-2
-
I--L
-ga0
-05
-B-3
-
~4L. *11 I-
is-
010
-103
-4B-4
-
405
01
Y p~i~t,4rCar1~- Ft. -
-15" - _, :
10
B-5
-
-101
B-
-
-'5
-I0v
-B-
-
r)-
0B-
-
Rl ID
20-
-o
0B-9
-
-50
-40-
8-10
-
Leo 1.o ~Zoo
I5 -
40
- I'
-- ..
-0 .. . ...
B-11
-
5LC A - )d 4 PO pP,
F= 1~ zo
5-
I0-0
0-
-4o-
-1Fi
B-1 2
-
pr
FHa)~~/Hc
-20
~k~a~M~oo~ I~iy -13~
-
-F= Pv-
-20-
-50-
B-14
-
PV-
40-5
10.20Caa
Ft~i~Lto5 B-105
-
-FA 4J.
-0 -
- I
TH=qaS- 0 - .'
(cv
-/0 --------.Jj.
-30 - -
- I vI~4.fe:;E~
.. . ... . ".. I .. . . . .
B-16
-
4p4-
o -
Kl-~
01
-30
-~v
-2e-
-30
B-1
-
0
R~ I
-0 -o- -... ..
-zo
-- 4o
-- eo .... t,
B-18
-
caw±F = Ii I
/ /_ ,to-.-I,50 --
-20- Cox
-30
..-.. .. . .. .....
- '1B-19
-
0-
-20-2
-
RL0
p-ZO
-4--- -.- "-'--
• -zo -
-30-
BI_
--jr - - 21
-
17 - 15
-0A 5,RI2~.. i00 .
-to
-20 - 0'
B-22
-
4,t05
-20-
-
rp0
-20-
B-24
-
6w~oAkH~ P4Ju4i, LA.
FL
--- 0
-300
B-25-
-
-15
O-0
-330
- s o - IL -
B-26
-
-5teaAA -
-0
-40
-2SB-
-
-10
-4o-
-
B-28
-
• .515 .
RL A' O
-2o
-40-
-45.
96p
-8-2
-40.- 1
t
8-29
-
[- -' 0 -
-10 -
-30
-2 0 - -i /-40-
-30'
Cite~
B-30
-
P~PV.
-/00
-4o
-45-
B-31
-
-5 -30
-0
-330
-20
z ,-4o - / ......
-3oL -., ,
- -in 4S-> L
TI
B-32;5
-
RL
-3o"
-2o = -_ ._.!. ..
I Z
4, -
B-33
-
gA .2 1A A L A
- ,16.2 r
RR
0 30
-2.0-6-JO-
-Z S ..-. ....
-30
B-34 it
: ie
Ii i
B-34
A
...... .. ...... - w d
-
~I-- 30
-30
3 41
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