Convert ArcGrid to GeoTIFF

[edsu]

In reviewing load_geoserver.rb we noticed that GeoTIFF was hard coded where it might sometimes need to be ArcGrid. We apparently don't have many ArcGrids and it might be possible for us to convert them to GeoTIFF, and simplify that parts of the robots that deal with ArcGrid?

This ticket is to explore how to convert them, and see if they work in GeoServer afterwards.

[kimdurante]

Have tried a few of these and seems to work with no issues.