QuickBird Imagery Processing using ArcGIS , ERDAS Imagine/LPS and GeoExpress 7

QuickBird Imagery Processing using ArcGIS, ERDAS Imagine/LPS and GeoExpress 7

QuickBird Imagery Processing using ArcGIS, ERDAS Imagine/LPS and GeoExpress 7Or, how I learned to stop worrying and embrace high-resolution imagery

Carrie GuilesAnn [email protected][email protected] National ParkWow, thats a lot of imageryCombination of several projects and divisions needing high-res imagery+End of year monies=1600 square Kilometers of QuickBird Ortho-Ready panchromatic/multispectral imageryImagery Order Area

Order breakdown by scene:

Breakdown of a single scene:

Wanted:orthorectified, 2-foot resolution multispectral imagery with less than 2 meter overall error. for background imagery in cartographic products and for heads-up digitizing of featuresNo problem! Someone HAS to have written a detailed how-to document for this!

Buyers RemorseRight?Found 30+ journal articles, but few clues and no step-by-step methodologiesProcessing StepsMosaic (unchip) by sceneSource your DEMOrthorectify the panchromatic and multispectral bandsPan-sharpen your multispectral imageryGeoreference using ground control points1) Mosaic (unchip) by sceneIn order to squeeze the imagery on to DVDs, Digital Globe splits up the scenes into tiles. Not an issue until you realize that the RPC files needed to orthorectify the imagery are delivered by SCENE not by tile. So you have to re-assemble the scenes before orthorectifying.

2) Get your DEM!

Cannot stress this enough - when using Imagine to orthorectify you NEED a DEM that does the following:

covers your full area of interest and

has horizontal and vertical reference EXACTLY the same as your imagery3) Orthorectify your panchromatic and multispectral imagesDone using the LPS Extension of ERDASUsing sensor and image information provided by scene, and using the DEM, you end up with 2 orthorectified images per scene (one panchromatic, one Multispectral)

4) Pan-sharpen

5) Final GeoreferencingAt this point, you should have a pan-sharpened, ortho-corrected image. If desired, you could have used any ground control points (GCPs) during the orthorectification process in Imagine. In our case, since the imagery follows road corridors and the spread of the available GCPs is linear, processing the imagery with GCPs at that point resulted in unsatisfactory products.Instead, we are using our network of ground control points to run georeferencing in ArcMap after the pan-sharpened product is finished. This adds an extra step to the process, but results in a higher quality image.

After final georeferencingerror of less than 1.5 meters using control points for verificationRecent points taken by geology field crew at Old Faithful are within 0.5 meters (using Trimble GeoXH)Contacted by NAIP processing crew, and they are using our GCP database to rectify the 2009 NAIP imagery.Old Faithful

Grand Prismatic Spring

A Bit About Ground Control PointsCollecting ground control points ad hoc for smaller projects has a long tradition at Yellowstone NP. We had many projects from GIS and Geology with GCPs scattered throughout project folders. With ~1600 km of high-resolution QuickBird imagery we realized that we had a choice: register the QuickBird to the existing NAIP imagery (with a ~3m accuracy in areas of low relief, ~7 m in high) or make the QuickBird imagery our best data set to which we could then register other imagery. We chose the latter.Volunteer Crews & Our GCP DatabaseUsed short-term volunteers to collect points over summer 2008 & 20091,200+ pointsNot all are usefulGround Control Fun: The Tree Man

And his cousin, Guardrail Guy

Lessons LearnedCheck for free imagery on the NGA WARP site and use the CIDR tool! (these are changing all the time)Order full scenes rather than by convoluted Area of Interest (such as buffers along roads)Purchase 2 external hard drives one to backup your data daily and one to work from. We used one 1 TB hard drive for processing and backed up to our network drive.When dealing with large amounts of imagery (multiple scenes), keep a log file of your imagery spreadsheet works fine. Most processing was done on a computer with a quad-core processor and 8 GB of RAM. We did spread the work around though, and some was done on dual-core processor with 2 GB of RAM. It just ran MUCH more slowly some processes will run for 8+ hours.Train your ground control point collection crew to a specific method before setting them loose with GPS units!

The AftermathAvailable upon request:How-to documents for the image processing and Ground Control Point collection31 .pdf reference papers used to create this methodology

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