gps area measurements - europa

Kick-off 2010, Ispra, 13-15 April 2010 1 / 24

GPS area measurements


Outlines

9 GPS devices certified by Navcert or validated by MS

9 Example of GPS validation tests in some MS

9 Direction effect and tree canopy

9 Differential correction: DGPS code versus VRS carrier phase


GPS devices certified by Navcert

1 new device certified since Nov 2009:

http://www.tuev-sued.de/navcert/en/certification_marks/ppp_80010

-> “ certificate expired” -> legal issue (certificate valid

if no technical change) -> no renewal from manufacturer

-> Manufacturers (Leica, Trimble) ready to certify their own equipment under JRC supervision

A (0,10m)vertexTopcon GRS-1 with Ascos PED real time correction service

Category (buffer)Measurement methodDevice


November 2009: 8 models validated

0,75vertex/continuousTrimble GeoXT with EGNOS SI

MS Device Method Buffer (m)

GR Garmin 60 continuous 1,25 (except if trees)

BG Magellan MobileMapper CX + voice application

vertex/continuous 0,75

CZ Topcon Legacy H – DGPS continuous 0,75

DE Topcon GMS 2 + Beacon vertex 0.75

UK Trimble Pro XRS (Beacon and OmniStarcorrections)

vertex <0,50

JRC (PL) Trimble GeoXT and GeoXH continuous 0,75

GPS devices validated by MS (with JRC support/review)

More info on webpage


April 2010: 13 models validated by MS

0,50vertexENTrimble Pro XRS with Omnistar corrections

0,50vertexENTrimble Pro XRS with Beacon corrections

0,75vertex/continuousSITrimble GeoXT with EGNOS correction

0,75continuous (1s)JRC (PL)Trimble GeoXH - standalone

0,75continuous (1s)JRC (PL)Trimble GeoXT - standalone

0,75vertexDE (Rheinlandpfalz)TOPCON GMS-2 with Beacon correction

services

0,75continuousCZTopcon DGPS reciever Legacy H

1,00vertex/continuousBGMagellan MobileMapper CE - standalone

1,00vertex/continuousBGMagellan MobileMapper CX - standalone

0,75vertex/continuousBGMagellan MobileMapper CX (with voice

application)

0,50vertexDKLeica SR530 with Leica Smart Net correction

0,50vertexDKLeica GS50 with Beacon correction

1,25continuousGRGarmin 60

0,75continuousDKAsus PDA + Haicom GPS antenna

Buffer width, mMeasurement methodMSDevice, type

http://marswiki.jrc.ec.europa.eu/wikicap/index.php/GPS_receivers_validated_by_Member_States


GPS validation: summary

9 Validation tests planned for 2010

-> Common questions from MS (CZ, FR, CY, LV) on test protocol

�Number & type of parcels (size, shape, border)?

�Number of repetitions, sets, operators?

-> 2 examples (JRC and SI)


Example 1 of experimental design: JRC test (PL, 2009)

Devices/Software tested:

Measurement protocol:

Device settings:

Trimble GeoXH (internal antenna)

with Terrasync version 3.30 Professional edition

Trimble GeoXT (internal antenna)

with Terrasync version 2.53 Professional edition

5410 (5days x

2op)26 (3 with trees on boundary)

DaysRepetitionsSetsOperatorsNo of parcels

Max PDOP:102010switched offcontinuous (1s)

DOPSNRElevation maskEGNOSMeasurement mode


Examples of fields used for validation tests in PL

Parcel A Area = 1,0ha, P=506mParcel BArea = 1,5ha, P=508mParcel C Area = 0,4ha, P=245mParcel D Area = 0,3ha, P=221mParcel E Area = 0,8ha, P=659mParcel FArea = 1,1ha, P=419m

The testing fields included different parcel size, shape and border obstruction

Area: 0.3 to 1.5 ha, Perimeter: 220 to 650m

~ 35-40 cm


Direction effect – case of test with Trimble Geo XT standalone

Parcel D: S=0,3ha, P=221m, 20 measurements (10 CW and 10 ACW), continuous mode

The parcel area when measuring in clockwise direction is constantly larger than the parcel area in anticlockwise

Result: Difference, expressed as an error on perimeter of 62cm (mean acw = -37cm, mean cw = 25cm) between measurements taken cwand acw

Possible reason: operators do not hold the antenna of the receiver on the field border -> can be eliminated by taking special care to the measurement protocol

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

err

or_

on_

peri

met

er

anticlockw ise clockw ise

direction

Each Pair

Student's t

0.05


0

0,2

0,4

0,6

0,8

1

1,2

borderpartially

obstructedby trees,

rectangularshape

borderpartially

obstructedby trees,irregularshape

borderpartially

obstructedby trees,

rectangularshape

openhorizon,

rectangularshape

openhorizon,

elongatedshape

openhorizon,squareshape

A B C D E F

GEO XT

GEO XH

Tree canopy influence on buffer width

R e

xpre

ssed

as

a bu

ffer

on

perim

eter

[m

]

Parcel type:

3 with obstructions

3 with open horizon

trees

Open horizon


Example 2 of experimental design: SI test (2009)

Devices/Software tested:

Measurement protocol:

Device settings:

Trimble GEO XT with EGNOS correction (Hurricane external antenna)

with ArcPAD version 7.0

749 (3 device x 3 op)37 (3 with obstructions)

DaysRepetitionsSetsOperatorsNo of parcels

0,75Min 4Max PDOP: 5YesStop and go/continuous (1s)

Buffer, mNb of satellites DOPEGNOSMeasurement mode


Test parcels in Slovenia

7 parcels (3 with trees)

Area: 0,1-1ha


Input needed by JRC for reviewing MS test1. If statistical analysis is to be made by JRC, MS

should send:

• A technical report with the following information9 Type and number of devices tested 9 Software/Firmware version9 Method of measurement (vertex/continuous)9 Device settings (elevation mask, max DOP, etc.) 9 Use of differential correction and type of correction9 Number of sets, repetitions per set, parcels (with trees), list of operators9 Sketch of the test parcels on orthophoto and photos of the parcels • Data9 A copy of the measurement protocol (parcel id, date and time, set, repetition,

operator, direction of measurement, area, perimeter measured)9 An excel sheet with the measurements9 The shp files and LPIS ortho-images of the area


Input needed by JRC for reviewing MS test

2. If statistical analysis is made by MS and is to be validated by JRC

-> MS should send

�technical report

�data�sheets with the statistical analysis

http://marswiki.jrc.ec.europa.eu/wikicap/index.php/GPS_equipment_-_validation


DGPS (code) vs VRS4km (carrier phase) – 2nd test

Purpose1. Comparison between a code phase and a carrier

phase differential correction of the GPS signal and their influence on area measurement

2. Continuation of the test in vertex mode (in 2009 test performed only in continuous mode)

Through local provider of differential corrections: GPS Lombardy (http://www.gpslombardia.it)


Design of experiment

9 Trimble Geo XH receiver9 One parcel inside JRC, 4 modes tested and

compared:

1. DGPS - differential code corrections (meteraccuracy) in continuous mode

2. DGPS - differential code corrections (meteraccuracy) in vertex mode

3. VRS4km - carrier-phase correction via Virtualstations (decimetre accuracy) in continuous mode

4. VRS4km - carrier-phase correction via Virtualstations (decimetre accuracy) in vertex mode


Test field

9 2 operators

9 2 days

9 6 sets (3x2op)

9 4 repetitions

(2 cw and 2 acw)


GPS tracks and measured areas 1/2

DGPS - continuous

DGPS - vertex

Receiver GeoXH+DGPS, Field B, cont : level

1

2 3

45

6

1550

1600

1650

1700

1750

Date of measurement

Mea

sure

men

t m

ean

and

rang

e,

sqm

accepted data

outlier data

overall mean

True_value

Receiver GeoXH+DGPS, Field B, vertex : level

1 2

3

4 5 6

1550

1600

1650

1700

1750

Date of measurement

Me

asu

rem

ent m

ean

a

nd

ran

ge,

sqm

accepted data

outlier data

overall mean

True_value

(Code)


GPS tracks and measured areas 2/2

Receiver GeoXH+VRS, Parcel B, cont : level

Set 1

Set 2

Set 3 Set 4Set 5

Set 6

1600

1650

1700

Date of measurementM

easu

rem

ent

mea

n an

d ra

nge,

sq

m

accepted data

outlier data

overall mean

True_value

VRS - continuous

VRS - vertex

Receiver GeoXH+VRS, Parcel B, vertex : level

Set 1

Set 2

Set 3Set 4

Set 5

Set 6

1600

1650

1700

Date of measurement

Me

asu

rem

ent

m

ea

n a

nd

rang

e,

sqm

accepted data

outlier data

overall mean

True_value

Higher variability in measured area


Tree canopy influence (vertex mode)

Open horizon

VRSDGPS

Trees

90 cm

75 cm

80 cm

10 cm


Statistical tests9 Outlier detection -> the data is free of outliers (only

strugglers were found but kept)

9 According to the analysis of variance the factor direction is significant for operator 1, VRS, continuous mode

9 The direction effect is omitted -> in terms of area is negligible

-0,1

-0,05

0

0,05

0,1

0,15

0,2

erro

r_on

_pe

rim

acw cw

Direction

All Pairs

Tukey-Kramer

0,05

ANOVA

Mean difference as error on perimeter

between

cw (5cm) and acw (-5cm) -> 10cm


ResultsThe overall reproducibility limit of the area measurements,expressed as a buffer on perimeter:

Comparison withthe test done in 2009:- Standalone mode - DGPS (code)- VRS (carrier)

0,230,26DGPS

0,160,25VRS

R limit - vertexR limit - contTrimble GEO XH

0

0,1

0,2

0,3

0,4

0,5

0,6

Standalone-2009

DGPS-2009 VRS-2009 DGPS-2010 VRS-2010

continuous

vertex

2009

2010

Buf

fer,

m

Std alone

Code CodePhase

Phase


Conclusions

9 Carrier phase differential correction does notimprove significantly the accuracy of area measurement in comparison with code correction

9 Use vertex mode with carrier phase differential correction

9 Both types of differential corrections improveaccuracy of area measurements in comparison with standalone accuracy: buffer category goes from 0.75m to 0.50 m


Pay attention to:• Direction effect ->special care to the protocol

• Include parcels with trees on the border

• You need 2-7 days and 2-6 operators

Do not hesitate to ask us for:9 Review of test protocol and plan

9 Statistical analysis of the data

9 Review of the whole test (if analysis of data made by MS)

Reminder on GPS validation tests

Thank you

gps area measurements - europa

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