advanced ortho image processing igic 2010. 2 advanced ortho image processing outline ■about surdex...

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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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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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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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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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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Initial Gamma Correction

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Solar Correction

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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)

advanced ortho image processing igic 2010. 2 advanced ortho image processing outline ■about surdex...

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