And the same process can be used with any “clean” raster area shapes, i.e. That can be done with free software, using a multi-step process. If I have a GIS program that lets me set one color in raster image as transparent, I can set white as the transparent image in the viewshed image, and overlay the viewshed on top of another image, perhaps a topo map:īut if the GIS program doesn’t allow raster color transparency, or if I want more flexibility in displaying the viewshed, it would be useful to convert it into a polygon shapefile. I can now open the viewshed image by itself in a GIS program. You can now save it as a GeoTiff with File => Save map as image => As GEOTIFF, screen scale. Zooming in to at least 1:1, or even greater, eliminates that problem (see this post for more info on how to zoom) the viewshed will be redrawn when you zoom in. If I save the image as is, it will be saved at the screen resolution, which will result in poor resolution (pixelation) at the edges. The terrain image has been blanked out, but the viewshed is still displayed as an overlay. If I right-click on the image, select “Display Parameter”, then “Blank”, I get the following image: I’ve turned off the symbol for the observer’s location, for reasons that I’ll explain later. There’s a somewhat painless way to do it with free software.įirst, here’s a viewshed created in MicroDEM, following the process outlined in the earlier post: You can do this with the Spatial Analyst extension for ArcGIS, but the two together are pretty expensive. More generally, the need might arise to convert a general raster image of an area into a polygon shapefile. But it could be useful to export the viewshed data alone, either in raster or shapefile vector format, for use in other GIS programs. In a previous post, MicroDEM was used to create viewsheds from a DEM (digital elevation model), and plot them on top of either a DEM terrain image or a corresponding map loaded into the program.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |