Reprojection and comparison of data
You have a number of issues with your data:
- The shapefile with the contour lines has a geographic coordinate system defined (coordinates in decimal degrees), however the data really has projected coordinates. It is important to know what the correct coordinate system of this data is and assign that correct coordinate system before you proceed.
- The other aspect is that the contour lines, are a result of some cartographic processing (Cul-de-Sac masking). It has holes in the major contour lines. You would need to correct this before interpolation (see Topo to Raster—Help | ArcGIS Desktop, Spatial Analyst or 3D Analyst required):
- I also found some residue of the legend in the lower right corner of you contour shapefile:
After you have assigned the correct projection Define Projection—Help | ArcGIS Desktop and have reprojected the data to be in the same projection as the DEM ( Project—Help | ArcGIS Desktop ) you can interpolate the contours Topo to Raster—Help | ArcGIS Desktop and calculate the difference between both DEM's Minus—Help | ArcGIS Desktop
Here's the screen shot of the CAD file legend
Just looked up that PRS## is for the Philippines. And it is based on the Luzon datum.
There are several zones with their own central meridians. So you need to know which zone.
And use the correct transformation between Luzon and WGS.
Too much detail I'm sure....
So currently the contour shapefile coord sys is defined like this :
But you can see from the extent tab, that this cannot be true.
Those numbers don't look like decimal degrees to me (too big).
So, redefine it like this:
Right click on the shapefile in Catalog (don't have it open in ArcMap at the same time).
Use the search to find "PRS", in projected coordinate systems.
