Collaborating in geospatial context since 2000!

Wednesday, July 23, 2008

Multi-band Raster GeoPDFs

Over the past few months, the raster team has been working hard to iron out the plans for the next generation of Map2PDF for Raster. There have been many interesting developments that have come out of it like adding the ability to query for and display more than just 3 bands of base data at a time. I posted an article about creating a GeoPDF out of AVIRIS data with 224 bands and got mixed reviews as to why this would be useful. The problem was with the way we used Adobe's blend modes when interactively turning visual bands on and off in Adobe Reader. There are quite a few blend modes to choose from and most of them are not applicable to the world of GIS and Remote Sensing! It's ok though as we have found a couple methods that work and are actually pretty useful.
  1. Difference: Subtracts the darker of the two constituent colors from the lighter color (which is the background for the PDF).
  2. Exclusion: Produces an effect similar to that of Difference mode but lower in contrast.
In previous examples, I used blend modes that completely covered the base map data with other bands of sensor data. The Hyperspectral example was ultimately botched because of this. Well...that and we were not stretching the histogram for each band added after the RGB base map.

The graphic that you see below represents a very small QuickBird scene with an IR band that is displayed as Band 4 in the Layers Tab. Open the PDF and click on the Layers Tab to see how blending modes are implemented in the PDF space. This PDF was created with low image quality to save space!

Download the GeoPDF Toolbar to gain access to all the spatial information!


Labels: , ,


Post a Comment

<< Home