arcgis-desktopcontoursaga
I have a vector dataset of mean annual precipitation polylines, and I would like to generate a raster from them. I'm not sure the best way to go about it.
ArcGIS has the Polyline to Raster tool but from reading its help file I get the impression it's not really designed to do what I need it to do. Obviously some kind of interpolation is required.
I am hoping that SAGA-GIS might have a useful module. Either that or I guess I could convert the lines to points and then krige them.
I would highly recommend going through the Contour lines to DEM tutorial, available from GRASS wiki. Essentially, they describe different interpolation methods used to produce a DEM. Avoid IDW interpolation using contour lines (i.e. described in one segment of the tutorial) since this is an inappropriate use of the interpolation method. The GRASS module r.surf.contour is probably what you are looking for--more details about the module available here. Their tutorial shows a pretty good interpolated DEM from rasterized contour lines:
As Jay Guarneri mentionned, you can export to GeoTIFF using the Import/Export - GDAL/OGR module and GDAL: Export Raster to GeoTIFF which will create a TIF image.
Another nice way is to create a virtual raster that can be loaded in ArcGIS (verion 10 and above, I think). Virtual raster is essentially an xml file describing your raster and pointing to it. So it's not a copy, and if you update the original raster content, you'll update the vrt at the same time (except if you play with dimensions or projection). You go in Import/Export - GDAL/OGR > GDAL: Export Raster and set Format option to Virtual Raster. It's the equivalent of
gdal_translate -of VRT in.sdat out.vrt
That way you can work on your raster in saga and you just need to reload it in ArcGIS to update. No need to export it every single time.
Best Answer
Giving you GRASS and GDAL based answer if that's an option for you.
GRASS - r.surf.contour is the tool meant to interpolate contours to create DEM. http://grass.osgeo.org/wiki/Contour_lines_to_DEM#r.surf.contour
If using GDAL is an option, try this. ( Install OSGeo4W and run following from shell ). This is an easier option, but kind of a hack, so use with care.
Assuming your isolines layer is called isoline.shp and your polylines have an attribute named PRECIPITATION
Convert to raster , X is the resolution of the output raster
gdal_rasterize -a PRECIPITATION isoline.shp iso_raster.tif -tr X X
Fill intermediate values by interpolation, change XX to appropriate value.
gdal_fillnodata.py -md XX iso_raster.tif iso_raster_interpolated.tif -mask iso_raster.tif