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Tuesday, December 30, 2008

Change Detection with GeoPDF

By definition, change detection in most remote sensing software applications is the calculated difference between two images of the same or similar spatial extent. The output from that calculation is another image that highlights the changes that might exceed a user-specified threshold. This is very useful in those instances where your decision makers need to see before and after images of a partcular area. A good example of this was with the large-scale devistation from a Category 3 Hurricane known as Katrina which swept through the city of New Orleans back in 2005. Below, you can see that we are able to mashup recent and archived imagery to perform an accurate analysis of the area in a single PDF file. I created this particular file from QuickBird data acquired on June 23rd 2005 and then on September 3rd 2005 which gives us a good before and after shot of this area in New Orleans.

With GeoPDF, we are able to stack several GIS layers (both raster and vector) on top of each other in a single PDF file. We are also able to view multispectral data by manipulating the image band combinations all in the same GeoPDF file. As you can see below, we switched from true color to color infrared (false color) on the fly to help identify vegetation that was damaged in the storm.  

Once the GeoPDF has been compiled and delivered down range, it can be marked up and then sent back to a GIS Analyst to help make better and more informed decisions about how to respond! Or, the opposite of that can be applied here as well and a non-GIS savvy respondant hired to do "GIS" work can mark up the PDF before sending it out to save time down range.

Set PDF Bookmarks to display specific areas of interest to your audience! Refer to this previous post for more of what can be done using Adobe Bookmarks...

Happy New Years Everyone!

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Anonymous GIS Services said...

Very useful and informative post.
I really enjoy this blog and the insight from everyone who participates.keep on posting.
Photogrammetry and remote sensing

1:19 AM EST


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