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Archive for March, 2011

Historical USGS Quads

Posted by smathermather on March 4, 2011

This will be a very quick post today.  We wanted to use some historical USGS quads for analysis.  We had a ready source, used ArcGIS to georeference them to a grid, but then wanted something approaching a seamless product.

Enter gdal.

First step, create an image to put the mosaic into:

gdal_merge -o usgs_merge.tif -createonly input1.tif input2.tif ...

Then mosaic into that.  Since we have a shapefile with the shape of the bounds of each of the images in question, we can use a cutline to perform the mosaic, e.g.

gdalwarp -cutline quadrangle_index_24k.shp -cwhere "quadname_ = West_View" "West_View.tif" usgs_merge.tif

In all honesty, this was scripted in Excel for expediency, but could easily be done in Windows Command with for-in-do, or BASH at a UNIX machine.

Final result:

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