shrug-l: Orthoimage quality evaluation references?
johnsonj-gis at hotmail.com
Thu Jan 10 12:55:05 EST 2008
Can anyone point me to a book, article, or online reference that gets into the nitty-gritty of evaluating orthophoto quality? I'm specifically interested in looking at the histogram characteristics of an image as a guide to assessing the quality of the image or "troubleshooting" it.
The particular issue I'm looking at is some color TIFs of an urban area that look okay in ArcMap at the raster resolution (1:1200), but display very poorly when zoomed to smaller scales (1:5000). Pyramiding makes no difference. Display settings make no appreciable difference. What APPEARS to be the issue is that the white areas in the photos are VERY white. The histogram for each of the three bands in the image show very high numbers of 255,255,255 pixels. I theorize that this is throwing a wrench in ESRI's algorithm for resampling the image for display (cubic convolution). The really ODD thing is that the images look fine in PaintShop no matter what scale they are shown at...
In a more general sense I'm interested in how one would quantitatively assess an orthophoto vendor's product. Surely there must be guidelines of some sort that can be applied other than the "eyeball test"?
Not sure that understanding this problem will lead to its solution, but any insights would be welcome.
Jay Johnson, GISP
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