Mapping Center

Last week's blog post Filling in and clipping in a raster described how to fill in holes in a "bad DEM" using data from an existing "good DEM", then clip it to the outline of a feature.

The blog post suggested using some ArcGIS geoprocessing tools that available with the Spatial Analyst extension. As with most GIS operations, there is more than one way to get to the final answer! In this blog post, I describe how Map Algebra can be used to achieve the same results.

We can break this process down into three steps. Read More...

Sometimes you want to use raster data, like a digital elevation model (DEM), but it doesn't have the same exact extent as the area you are mapping. For example, if I use gtopo30 and "countries" data (available on the ESRI Data and Maps CD) to create map of the Pacific Northwest, the coastline boundaries do not coincide. In some places the elevation values are missing for inland areas, and in other places, there are elevation values outside the extent of the land area. So we need a way to clean up the data and make them coincide. Just clipping won't work as this won't add the missing elevation values.

I can fix all this if I have some other elevation data to fill in the missing interior elevation. For example, I can use etopo2 data (also on the Data and Maps CD) to get the elevation values for the pixels that need them. Read More...