- CONVERT RASTER TO VECTOR QGIS HOW TO
- CONVERT RASTER TO VECTOR QGIS DOWNLOAD
- CONVERT RASTER TO VECTOR QGIS FREE
In the copy layer, delete all of the areas that correspond to the original weapons fan image, leaving behind only the hole areas. Add the copy as a layer in MapWindow, along with the original. Make and rename a copy of this shapefile (all three files. For my example, I got this, with holes converted to extra polygon shapes instead of holes: If your original area didn’t have any holes in any of the polygons, you’re done in my case, it did, so I have to continue on. Delete the background shape, leaving only the fan areas and the hole areas.
CONVERT RASTER TO VECTOR QGIS FREE
Open the shapefile in a GIS editor that allows you to erase shapefiles with polygons from a different shapefile layer I’ll use MapWindow 4.4 for this example, since it’s free and has all the tools necessary for the following steps.ħ. Close SAGA, and don’t save the objects when prompted (click on Cancel).Ħ. Click on the shapes tab at the bottom left, right-click on the shape layer, and save it as a shapefile. If I had left the observer’s position marker on the original viewshed, it would have vectorized that as well, so that’s why I turned it off. SAGA will vectorize everything in sight into shapes, including the background and any holes in the GeoTiff. Click OK, and be prepared to wait a few minutes for the operation to conclude, even though there’s no visible sign of progress you’ll hear a sound when it’s done.ĥ.
Choose the image you’ve just imported (renamed by the program to “Unnamed) as the input grid, and check that “Output as …” is set to the default of “Polygons”.Ĥ. Select Modules => Grid => Shapes => Vectorising Grid Classes. Start up the program by double-clicking on “saga_gui.exe” open the GeoTiff created above (Modules => File => Grid => Import => Image, then select the file by clicking on (null), set Split Channels to “False”, and click OK).ģ.
CONVERT RASTER TO VECTOR QGIS DOWNLOAD
Download SAGA 1.2 or SAGA 2.0 from the website, and unzip it into its own folder. In MicroDEM, after zooming in on the viewshed, save it as a GeoTiff as before.Ģ. colored shapes against a uniform background, preferably white.ġ. 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.
CONVERT RASTER TO VECTOR QGIS HOW TO
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.
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