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 jonchris@usgs.gov

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

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

Exploratory Research (cont.)

Exploratory Research (cont.)

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 with ground 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!

EDC Range

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 Stensaas stensaas@usgs.gov (605) 594-2569 USGS EROS Data Center http://edc.usgs.gov/ Commercial Remote Sensing Characterization, Calibration, Verification, and Validation (C2V2) Project