1. ASPRS Panel on Digital Sensor Calibration/Evaluation
USGS Early Testing Efforts of Digital Camera Systems
May 26, 2004
Jon Christopherson, SAIC
USGS EROS Data Center

2. Background USGS has been calibrating film cameras since 1973
Optical Science Lab at USGS HQ in Reston, VA
Uses multi-collimator assembly developed in 1953
Metric aerial film cameras very flat, very stable

3. 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+)

4. 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)

5. 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

6. Exploratory Research

7. Exploratory Research (cont.)

8. Exploratory Research (cont.)

9. 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?

10. 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

11. 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

12. MTF Characterization
EDC working with SDSU to develop MTF characterization tools & software
In lab using ISO 12233
In-situ with ground targets
Ease-of-use

13. 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?

14. 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!

15. EDC Range

16. EDC Range
Targets patterned after OSU range

17. 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.

18. Contact Information
Gregory L Stensaas (605)
USGS EROS Data Center
Commercial Remote Sensing
Characterization, Calibration, Verification, and Validation (C2V2) Project