selected characteristics of nri aerial photos … a brief introduction …

Selected Characteristics of Selected Characteristics of NRI Aerial PhotosNRI Aerial Photos

Selected Characteristics of Selected Characteristics of NRI Aerial PhotosNRI Aerial Photos

… … a brief introduction …a brief introduction …… … a brief introduction …a brief introduction …

Characteristics of NRI Aerial PhotosCharacteristics of NRI Aerial PhotosCharacteristics of NRI Aerial PhotosCharacteristics of NRI Aerial Photos

A Few Selected Terms Formats, Spectral Sensitivity, and Scale Scale, Flying Elevation, and Footprints Fiducials and Other Photo Markings Intro to Photo Geometry and the Single

Point Perspective Resolution Orientation of Photos for Scanning Use, Care and Storage of Photos

A Few Aerial Photo TermsA Few Aerial Photo TermsA Few Aerial Photo TermsA Few Aerial Photo Terms

Frame (also known as Metric or Mapping) Cameras Shutter exposes the entire frame at a

single instant Calibrated in a laboratory to determine

internal geometry focal length lens distortion

9 inch by 9 inch film

A Few Aerial Photo TermsA Few Aerial Photo TermsA Few Aerial Photo TermsA Few Aerial Photo Terms

Focal Length Distance (along the optical axis) from the

camera lens to the plane of sharpest focus

Lens

Focal length

A Few Aerial Photo TermsA Few Aerial Photo TermsA Few Aerial Photo TermsA Few Aerial Photo Terms

Vertical Photography Camera axis is < 3° from vertical

Oblique Photography Camera axis is > 3° from vertical Low oblique—no horizon High oblique—includes horizon

Ca m

er a Axi s

Cam

era Axis

Camera Axis

Aerial Photo Formats, Spectral Sensitivity & ScaleAerial Photo Formats, Spectral Sensitivity & ScaleAerial Photo Formats, Spectral Sensitivity & ScaleAerial Photo Formats, Spectral Sensitivity & Scale

Formats: Color film positive One photo per NRI site Monoscopic

Spectral Sensitivity: Natural color Color Infrared

Scales: 1:7,920 1:12:000 1:15,840

Scale, Flying Elevation, and Ground Scale, Flying Elevation, and Ground DistanceDistanceScale, Flying Elevation, and Ground Scale, Flying Elevation, and Ground DistanceDistance

lens elevatio

n

7,920 ft

6,000 ft

3,960 ft

Photo Scale = focal length/height above ground1:7,920 = 6”/3,960’1:12,000 = 6”/6,000’1:15,844 = 6”/7,920’

Ground Distance = Photo Distance/Photo Scale5,940’ = 9”/1:7,9209,000’ = 9”/1:12,00011,880 = 9”/1:15,840

5,940’

9,000’11,880’

Not to scale

Photo FootprintsPhoto FootprintsPhoto FootprintsPhoto Footprints

NOTBURNEY, CALIF.SCALE 1:24000

N4052.R-X00XX00X

TUESDAY, 1992

NOTBURNEY, CALIF.N4052.R-X00XX00X

TUESDAY, 1992

POL YCO MI CAL PROJ ECT IONBASED O N N EARLY NO DAT UMLKJ ALKJ LKJKJ EWR OIN VJNALAI LENV9 2 F ALK 93 OL AK LSLKA UKJF AL LS'ALSK KJSL A EI L KJF A; SL KJF AA

XXOO XXOO X99 34 .2

0 1/2 1 MILE1

Map

Footprint: the perimeter of the area covered by an aerial photo.

Small Scale Footprint (large area covered, features appear small)

Large Scale Footprints (small area covered, features appear large)

NRI Aerial Photography FootprintsNRI Aerial Photography FootprintsNRI Aerial Photography FootprintsNRI Aerial Photography Footprints

Approximate Coverage of NRI Photos

• 1:7,920• 5,940’ x 5,940’• 810 acres

• 1:12,000• 9,000’ x 9,000’• 1,860 acres

• 1:15,840• 11,880’ x 11,880’• 3,240 acres

• Nominal 160 acre area segment

FiducialsFiducialsFiducialsFiducials

Fiducials: permanent reference points exposed onto the photograph.

Principal Point (PP): Center of photo—found by intersection of lines drawn between opposing fiducials.

Nadir: image of point directly below airplane at time of photo (Nadir will equal PP for vertical photos).

Data Strip: varies in appearance and location by camera, but usually contains an altimeter and clock.

Other Photo Markings - Data StripOther Photo Markings - Data StripOther Photo Markings - Data StripOther Photo Markings - Data Strip

altimeter clock

State FIPSCode

County

State

Segment #

Nominal Scaleto nearest 1000.Not to be trusted formeasurements!

Agency Name Date

NOTE: Standard title block info is oriented to the North on NRI photographs.NOTE: Standard title block info is oriented to the North on NRI photographs.NOTE: Standard title block info is oriented to the North on NRI photographs.NOTE: Standard title block info is oriented to the North on NRI photographs.

Other Photo Markings—Standard Title BlockOther Photo Markings—Standard Title BlockOther Photo Markings—Standard Title BlockOther Photo Markings—Standard Title Block

State

Segment #

Nominal Scaleto nearest 1000.Not to be trusted formeasurements!

Agency NameDate

Other Photo Markings—Automated Title BlockOther Photo Markings—Automated Title BlockOther Photo Markings—Automated Title BlockOther Photo Markings—Automated Title Block

County

FIPSNorth Arrow

Time

EXAMPLE 1EXAMPLE 1

State

Segment #

Nominal Scaleto nearest 1000.Not to be trusted formeasurements!

Agency Name

Date

Other Photo Markings—Automated Title BlockOther Photo Markings—Automated Title BlockOther Photo Markings—Automated Title BlockOther Photo Markings—Automated Title Block

FIPS North Arrow

EXAMPLE 2 EXAMPLE 2

Latitude and Longitudeof photo center

Other Photo Markings—Camera # and Focal LengthOther Photo Markings—Camera # and Focal LengthOther Photo Markings—Camera # and Focal LengthOther Photo Markings—Camera # and Focal Length

Camera # Focal length mm

Other Photo Markings: vary in appearance and location but usually include calibrated lens focal length, camera number, and/or lens number. The camera # or lens # is needed to find the camera calibration report.

EXAMPLE 1EXAMPLE 1

Other Photo Markings—Camera #Other Photo Markings—Camera #Other Photo Markings—Camera #Other Photo Markings—Camera #

Camera #

Other Photo Markings: vary in appearance and location but usually include calibrated lens focal length, camera number, and/or lens number. The camera # or lens # is needed to find the camera calibration report.

EXAMPLE 2EXAMPLE 2

Other Photo Markings—Camera # and Focal LengthOther Photo Markings—Camera # and Focal LengthOther Photo Markings—Camera # and Focal LengthOther Photo Markings—Camera # and Focal Length

Camera #

Other Photo Markings: vary in appearance and location but usually include calibrated lens focal length, camera number, and/or lens number. The camera # or lens # is needed to find the camera calibration report.

EXAMPLE 3EXAMPLE 3Focal length mm

Photo Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point Perspective

ObliquePerspective

OrthographicPerspective

Single PointPerspective

Photo Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point Perspective

OrthographicPerspective

Single PointPerspective

If scale and orientation are known, distances and bearings can be measured directly:

Photo scale varies with relief and objects at different elevations are displaced relative to one another, thus distances and bearings are more difficult to measure directly:

Photo Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point Perspective

Single PointPerspective

The photo scale is different at the tops of the buildings than at the street level. The tops of the building are displaced radially outward relative to their location at the street.

Photo Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point Perspective

More than just buildings…

The clearcut boundaries (right) are straight lines on the map and ground

Higher elevations are displaced radially outward (relative to lower elevations)

Photo Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point PerspectivePhoto Geometry--Single Point Perspective

Distortion: error resulting from lens imperfections, camera tilt, poor camera vacuum, etc.

Displacement: the result of projecting a 3-D world (with varying heights) on a 2-D surface from a single point perspective. Allows for stereo viewing, however, NRI photos are not

acquired in stereo Orthorectification: For the NRI, scale

variation, relief displacement, camera orientation, and lens distortion must be removed for accurate measurement of lengths and areas.

Original Photo Orthorectified Photo

Photo Geometry--OrthorectificationPhoto Geometry--OrthorectificationPhoto Geometry--OrthorectificationPhoto Geometry--Orthorectification

Resolution of Aerial PhotographyResolution of Aerial PhotographyResolution of Aerial PhotographyResolution of Aerial Photography

Resolution Smallest feature which can be detected With film, resolution is expressed as Line pairs per

millimeter (lp/mm) or Ground Resolved Distance (GRD) Photography has the most resolving power of any remote

sensing system Mapping frame cameras and films used for the NRI under

ideal conditions can typically resolve about 100 lp/mm GRD = reciprocal of image scale/system resolution. Example: the calculated GRD of a 1:7,920 NRI photo is

7,920/ (100 lp/mm) = GRD 79.2 mm or 3.1 inches

Digital or scanning resolution is expressed as Ground Sample Distance (GSD) which is the size of the pixel in ground units

GSD = reciprocal of image scale/scanning resolution Example: the calculated GSD of a 1:7,920 NRI photo is

7,920/600 dpi = GSD 13.2 inches

Resolution of NRI Photos at Various ScalesResolution of NRI Photos at Various ScalesResolution of NRI Photos at Various ScalesResolution of NRI Photos at Various Scales

Scale GRS 100 lp/mm

GSD 600 dpi scan

7,920 3.1” 13.2”

12,000 4.7” 20.0”

15,840 6.2” 26.4”

MicroTeck 9800XL Scanner ConsiderationsMicroTeck 9800XL Scanner ConsiderationsMicroTeck 9800XL Scanner ConsiderationsMicroTeck 9800XL Scanner Considerations

Standard desktop scanners like the MicroTek 9800XL can do an excellent job of scanning NRI photography.

Limitations of desktop scanners for NRI include:

Less geometric accuracy than photogrammetic scanners

No option for unattended roll film scanning

Advantages of desktop scanners for NRI include:

Cost $1,800 vs. $100,000+ for a photogrammetric scanner

Geometric accuracy acceptable for natural resource projects

The MicroTek is capable of scanning at 1,600 dpi, but testing has shown that 600 dpi is adequate for the NRI.

Orientation of Film on the ScannerOrientation of Film on the ScannerOrientation of Film on the ScannerOrientation of Film on the Scanner

All NRI photos are scanned with North to the top.

The relationship of North to the film markings varies depending on: Flying direction. NRI photos can be flown

North-South, South-North, East-West, or West-East.

Type of camera The following slides will help you

determine the proper orientation.

Top of the ScannerTop of the ScannerTop of the ScannerTop of the Scanner

The front of the scanning bed is considered the top.Place the North end of the photo face down toward front of the scanner

Place North Edge Here

The NRI photography contract specifies that the photo is to be titled on the North edge.

What to scan? Scan the entire piece of film including the data strip and fiducial marks.

North Edge – Standard Title Block – Example North Edge – Standard Title Block – Example 11North Edge – Standard Title Block – Example North Edge – Standard Title Block – Example 11

Standard Titling on North EdgeStandard Titling on North Edge

The NRI photography contract specifies that the photo is to be titled on the North edge. Notice that this photo has the data strip on the opposite end from the previous slide.

What to scan? Scan the entire piece of film including the data strip and fiducial marks.

North Edge – Standard Title Block – Example North Edge – Standard Title Block – Example 22North Edge – Standard Title Block – Example North Edge – Standard Title Block – Example 22

Standard Titling on North EdgeStandard Titling on North Edge

Automated titling varies. Look for the North arrow to determine the correct orientation.What to scan? Scan the entire piece of film including the data strip and fiducial marks.

North Edge – Automated Titling – Example 1North Edge – Automated Titling – Example 1North Edge – Automated Titling – Example 1North Edge – Automated Titling – Example 1

Automated titling varies. Look for the North arrow to determine the correct orientation.What to scan? Scan the entire piece of film including the data strip and fiducial marks.

North Edge – Automated Titling – Example 2North Edge – Automated Titling – Example 2North Edge – Automated Titling – Example 2North Edge – Automated Titling – Example 2

Automated titling varies. Look for the North arrow to determine the correct orientation. Notice this is actually a West arrow. The photo is oriented correctly with West to the left and North to the top.

What to scan? Scan the entire piece of film including the data strip and fiducial marks.

North Edge – Automated Titling – Example 3North Edge – Automated Titling – Example 3North Edge – Automated Titling – Example 3North Edge – Automated Titling – Example 3

Use, Care and Storage of Aerial PhotosUse, Care and Storage of Aerial PhotosUse, Care and Storage of Aerial PhotosUse, Care and Storage of Aerial Photos

Proper Handling of Photographic Materials

Cleaning Storing and Archiving

Additional Notes

Proper Handling of Photographic MaterialsProper Handling of Photographic MaterialsProper Handling of Photographic MaterialsProper Handling of Photographic Materials

Things you can do to protect your photographicmaterials… Keep your work environment and tools clean Wear lint-free gloves Keep photos in protective sleeves Store photos under the best possible conditions Have copies made if you plan to use them in

the field Keep transparencies clean REMEMBER! The NRI photo transparency is the

original film from the camera. No backup copies exist.

If you have to ship an original NRI photo, use FedEx and declare a value

Proper Handling of Photographic MaterialsProper Handling of Photographic MaterialsProper Handling of Photographic MaterialsProper Handling of Photographic Materials

What can damage photographic materials? Fingerprints, dirt, dust, moisture, mold and

prolonged exposure to lights can threaten their quality or worse, render them useless.

Cleaning and Repairing Photographic Cleaning and Repairing Photographic MaterialsMaterialsCleaning and Repairing Photographic Cleaning and Repairing Photographic MaterialsMaterials

Acceptable Cleaning Materials Cotton Fabric

White or light colored Anti-static cloths are ok as well

Soft-Bristled Brushes Flat, camel’s hair Create a static charge by brushing the bristles over

a plastic rod such as a pen

Compressed Air Make sure the air is filtered to avoid sandblasting

and oil spots Solvents

Isopropyl alcohol—98% purity or higher!!! Ethyl alcohol—98% purity or higher!!!

Cleaning Photographic MaterialsCleaning Photographic MaterialsCleaning Photographic MaterialsCleaning Photographic Materials

Good ventilation and sufficient air flow Use soft, lint-free cleaning fabric (cotton) Test a discrete area before you begin

Moisten, clean and re-moisten with solvent—DO NOT SATURATE YOUR PHOTOGRAPH!

Clean one small area at a time Repeat if needed, but be conservative in

your cleaning approach!

Protect from light sources Use proper storage containers

i.e., metal or archival grade safe boxes

Do not stack or pack tightly to avoid pressure on your prints and negatives

Interleave them with acid-free paper

Use moisture-proof storage envelopes

Control temperature and humidity

Avoid storing them near heat sources or ozone-generating machines i.e., photocopiers

Silica gel packets help to dehumidify

Storing and Archiving Photographic MaterialsStoring and Archiving Photographic MaterialsStoring and Archiving Photographic MaterialsStoring and Archiving Photographic Materials

Packing Materials Use proper storage

containers i.e., metal or archival grade safe boxes

Avoid using original packaging—it will break down over time and damage your photographic materials

Storage Location Main or upper floors and at

least 6 inches (15 cm) above the floor

Protect against fire Fireproof storage vaults Fire cabinet or safeThey must be able to prevent

temperatures from rising above

100°F (38°C)

Additional NotesAdditional NotesAdditional NotesAdditional Notes

Unlike unprocessed film, prints are not affected by x-rays i.e., airport security

Do not store black and white and color negatives together in the same envelope

Do not use markers to write on the film or protective sleeve!

SummarySummarySummarySummary

Brief introduction to photo characteristics Formats, film types, range of scales Footprints Photo Markings (title block, fiducials, focal

length) Photo Geometry

Scale varies with relief Radial displacement

Photo Resolution Orientation for scanning Proper Storage