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AdvancedAdvancedOrtho Image ProcessingOrtho Image Processing
IGIC 2010IGIC 2010
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Advanced Ortho Image ProcessingAdvanced Ortho Image Processing
Outline
■ About Surdex■ Digital Acquisition Trends■ Image Processing■ Image Processing Approach■ Questions and Answers
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Advanced Ortho Image ProcessingAdvanced Ortho Image Processing
Surdex
■ Surdex headquartered in St. Louis, MO area■ Over a half-century of photogrammetric mapping
~100 employees7 aircraft – 4 Cessna 441 (Conquest) Turbine Aircraft3 Intergraph Digital Mapping Cameras (DMC)5 film camerasLiDAR
■ Very progressive R&DLarge amount of proprietary algorithms and softwareFocus on cost-efficiency and performance
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Surdex’s Digital Camera
■ Own and operate 3 Intergraph DMCsDigital Mapping CameraOperated since summer, 2005
■ Large-format digital frame cameraSimultaneous capture of panchromatic, color, near infrared12 bits/pixel potential dynamic range500MB per exposure
■ >600,000 exposures processed
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Multispectral Imagery (Minnesota NAIP, 2008)
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Advanced Ortho Image ProcessingAdvanced Ortho Image Processing
Multispectral High-Resolution Imagery
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~3” Resolution (Ottawa, Canada, 2007)
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Digital Imaging – From 4+ Miles Up
2’ DOQQ & Close-Up
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Digital Acquisition Trends
■ Film digital faster than most “experts” imagined40+ large-format digital cameras in North AmericaDoubled in last 3 yearsNumerous companies have completely abandoned filmFilm suppliers reducing emulsion offerings
■ Trends Increasing demand for “4-band” (R,G,B,NIR) Increasing demand for stereo Increasingly aggressive schedules
■ Many operators have developed their own software
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Image Processing for Results
■ What does the client want?Pretty picture?Support detailed GIS analysis?Match the last project?Hardcopy or softcopy?
■ Client must be involved in establishing “colorimetry”Color – easiest to establishContrast – affects brightness and sharpnessBrightness – interlocked with contrast
■ Digital imagery – “what color do you want?”
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Resolutions & Flying Height
0.4’ (4,000’) 0.5’ (5,000’) 0.6’ (6,000’) 0.7’ (7,000’) 0.8’ (8,000’)20% low nominal 20% high 40% high 60% high
Actual Surdex DMC Test ImageryAll Exposures Taken Within ~1 Hour Timeframe
All Remapped to (target) 0.5’ GSD
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Color Variation
Courtesy ITT Space Systems
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Calibrated Monitors are a Must!
Courtesy ITT Space Systems
Actual Pictures of Same Image on Different Monitors!
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Linear CCD response needs correction
Gamma(Logarithmic)
Correction
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Advanced Ortho Image ProcessingAdvanced Ortho Image Processing
Processing of Digital Imagery
■ Use reference images from acquisitionWork with client to get the desired lookLock down “colorimetry” before production begins
■ Why?Client has ownership in what deliverables look likeLess alteration of the imagery in the last stepLess re-work, better performance (schedule)Reduces QC to accuracy and artifact scrutiny
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Advanced Ortho Image ProcessingAdvanced Ortho Image Processing
Key Points
■ Technicians sort raw images into “groups”Geopositioned using ABGPS/IMUCommon scene characteristics1,000’s of images loaded at once
■ Enhancements are prototyped■ Batch-processing in distributed environment■ 12bpp processing – option to output to 8bpp■ 4-band processing to output color and CIR
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Processing
■ Gamma correction Initial targeting of image metrics
■ Digital dodgingOffset atmospheric hazeOffset localized brightness/contrast variations
■ Solar correction (“hot spot” removal)Offset solar illumination (especially for high-altitude)Aided by sun ephemeris data and ABGPSAutomated with operator override
■ Full 12 bpp processingOption to output in 8 bpp at completion
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Image Processing Flow Example (NAIP08)
1. Grouping of images2. Gamma correction3. Correct to color metrics
Dodging to remove local variations
Solar correction tooffset sun illumination
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Uncorrected12-bit Raw Image
Image Processing Flow
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Image Processing Flow
Initial Gamma Correction
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Image Processing Flow
Solar Correction
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Image Processing Flow
Digital Dodging
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Pre-Production vs Final Product – “WYSIWYG”
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Effectiveness of the Approach
■ NAIP 20096 states -- ~540,000 sq mi~100,000 exposures acquired @ ~34,000’ MSL~38,000 DOQQs @ 1m resolution X 4-bands5.5 months from acquisition through final delivery
■ Despite incremental product processing:Achieve overall state consistencyAchieve “national” consistency
■ The keys:Reference imagery processColorimetry established before production
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Delivering Seamline Data
■ New deliverable to all clients■ Seamline polygons with attributes
Date/time of acquisitionCamera & aircraft IDsSize of polygon
■ Why?Provide guidance to client or 3rd party QC – most errors are
related to seamlinesProvide a date for each pixel – desired by some for historical
reasons
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Common Seamline Error – and Resolution
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Seamlines – Spokane, WA 2009
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Closing Comments
■ Clients and contractors must work together to establish colorimetry prior to productionNo surprises upon deliveryAssures scheduleReduces cost
■ Take advantage of the content of digital sensors12bpp == 8X more data than scanned film4-band (color + CIR)