U.S. Department of the InteriorU.S. Geological Survey

ASPRSPanel on Digital Sensor

Calibration/Evaluation

USGS Early Testing Efforts of Digital Camera Systems

May 26, 2004

Jon Christopherson, SAICUSGS EROS Data Center

jonchris@usgs.gov

Background

USGS has beencalibrating film cameras since1973 Optical Science

Lab at USGS HQ in Reston, VA

Uses multi-collimator assembly developed in 1953

Metric aerial film cameras very flat, very stable

Laboratory Calibration Research

June ’03 - Control point cage installed at EDC Contract w/ Pictometry

Australis software used to determine camera coefficients

In early stages of research now Multiple cameras &

lenses have been tested (~10+)

USGS Digital Camera Testing

USGS facilities suitable for small- and medium-format cameras Ill-suited for most large-format systems

EDC has tested USGS camera plus selected few outside systems

Range from Medium-format, medium-expense systems (~$20K) to “pocket” cameras (< $1K)

Caveats!

The results presented here are from exploratory research only

Not meant to imply the quality of any camera/back/lens

These results are: Far from complete! Far from conclusive! However, they are a start and indicate areas of

interest for ongoing research

Exploratory Research

Sample Initial Results of Various Cameras & Lenses

-20

0

20

40

60

80

100

0 5 10 15 20 25 30

Radius from FPA Center (mm)

Dis

tort

ion

(p

ixe

ls)

14n 60mm Micro

D1X 20mm (30.1mm eff) FOV

Contax Megavision, 35mm

Contax 645C, 35mm

Minolta Dimage 71 zoom (7mm)

Exploratory Research (cont.)

Radial Distortion (in pixels) by FOV angle

-40.0

-20.0

0.0

20.0

40.0

60.0

80.0

100.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

Half-angle Field of View (degrees)

Ra

dia

l D

isto

rtio

n (

pix

els

)

Kodak 14n, 60mm Micro

Contax/Megavision, 35mm

Contax 645C, 35mm

Nikon D1X, 20mm

Minolta Dimage 7i, Zoom (7mm)

Exploratory Research (cont.)

Angular Distortion Across FOV

-0.500

0.000

0.500

1.000

1.500

2.000

2.500

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

Field of View (Half-angle)

Rad

ial

Dis

tort

ion

in

deg

rees

Kodak 14n 60mm Micro

Contax Megavision 35mm

Contax 645C 35mm

Nikon D1X 20mm

Minolta Dimage 7i Zoom (7mm)

Interim Observations

No system tested approaches the flatness of film metric cameras

Repeatability of results varies with system Variability can likely be controlled – on

some systems only Concern – can calibrations be trusted

over time?

Interim Observations (cont.)

In General: the more “consumer” the less “metric” The less “consumer” the more expensive

There is potential for small- and medium-format metric sensors Potential for great benefits in size, cost, speed,

ease-of-use Possibilities with new aerial platforms

Continued investigation warranted

Near-Term Plans

Basic environmental testing (temperature, vibration) of EDC cameras Explore other camera/sensor types Explore methods to ensure stability

MTF Testing Both Lab & in-situ

Begin radiometric testing Validate all of above with In-Situ testing Enhance EDC photogrammetry capability

MTF Characterization

EDC working with SDSU to develop MTF characterization tools & software

In lab using ISO 12233

In-situ withground targets

Ease-of-use

Radiometric Testing

Start basic: measure s/n, linearity, stability

Would like to move farther Spectral profiling, monitoring Long-term stability

Can systems can deliver “calibrated” multispectral data? How to maintain performance?

EDC In-Situ Range

65 ea. targets in 4mi × 4mi area around EDC surveyed to ± 2cm absolute accuracy

Additional 65 targets in higher density pattern for testing in-situ camera calibration

Site contains operating CORS station Option to set to 1 sec. intervals

Site has been flown once at 6” resolution and at 2’ resolution We need more overflights!

EDCRange

EDC Range

Targets patterned after OSU range

Conclusions

USGS research is underway Small- and medium-format systems

are problematic, but there is promise USGS needs help exploring

techniques being used Partnerships, assistance with

overflights, cameras/sensors, etc.

Contact Information

Gregory L Stensaasstensaas@usgs.gov

(605) 594-2569

USGS EROS Data Centerhttp://edc.usgs.gov/

Commercial Remote Sensing Characterization, Calibration, Verification, and

Validation (C2V2) Project