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Wednesday, May 07, 2008

Map2PDF for Raster

The raster team at TerraGo has been hard at work at getting requirements in place for the next generation of Map2PDF for Raster. An example dataset has been put together to demonstrate how anyone can export a wide variety of raster data to GeoPDF. Follow the links below to see the PDF's that were created from Landsat TM data. You might also want to check out a more in-depth description of what the various Landsat TM band combinations are and why they might be useful.

Download these files and play around with them as you see fit. Note that you will have to download the free GeoPDF toolbar from the TerraGo website. Its always better to download these files to your desk top on the links below to download each GeoPDF.

  • 3,2,1 Band Combination: The "natural color" band combination.
  • 4,5,3 Band Combination: This combination of near-IR (Band 4), mid-IR (Band 5) and red (Band 3) offers added definition of land-water boundaries and highlights subtle details not readily apparent in the visible bands alone.
  • 7,4,2 Band Combination: This combination provides a "natural-like" rendition, while also penetrating atmospheric particles and smoke.
  • 4,5,1 Band Combination: Healthy vegetation appears in shades of reds, browns, oranges and yellows. Soils may be in greens and browns, urban features are white, cyan and gray, bright blue areas represent recently clearcut areas and reddish areas show new vegetation growth, probably sparse grasslands.
  • 4,3,2 Band Combination: The standard "false color" composite. Vegetation appears in shades of red, urban areas are cyan blue, and soils vary from dark to light browns.
  • All Bands: This one is really cool because you can interactively turn all the bands on and off.

What's next? Hyperspectral to GeoPDF?


Anonymous Anonymous said...

How to get the pixel values within GeoPDF from the source raster data?

1:54 AM EDT

Blogger George Demmy said...

In general, it's not easy to do. PDF page description was not designed with data preservation and reuse in mind. Notions of pixel values are punted entirely. An image is abstracted away to something opaque and contained in a little unit square. The square is then translated, rotated, and scaled to appear where it should on the page. To map from page position to pixel value it theoretically possible, but non-trivial.

However, there may be provisions for doing just that in Adobe's PDF library or with the Acrobat SDK.

For many applications of GeoPDF, pixel values are not particularly useful since very aggressive (and lossy) JPEG compression more than likely altered the original pixel values.

For classification data, pixel values are often what are thought of, but what really is important is if some point is in or out of a region that has been classified this way or that. Vectorizing the classified regions and assigning the appropriate metadata to the vector polygon is a work around for that use case.



8:08 AM EDT


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