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I am overlaying some WGS84 (EPSG:4326) coordinates over a few DEM rasters with EPSG:102710 (NAD_1983_STATEPLANE_NEW_HAMPSHIRE_FIPS_2800_FEET)

When they are these two different layer CRS the coordinates overlay perfectly where they are supposed to be, however, if I change the coordinates to have the same EPSG as the DEM rasters, then the coordinates are way off. What is the explanation for this?

The rasters were from this site: http://www.granit.unh.edu/data/search. "Digital Elevation Model - Quad 54" for example.

Unfortunately, I cannot provide the coordinates.

marked as duplicate by Dan C, csk, whyzar, JGH, Jochen Schwarze Oct 18 '18 at 13:14

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    Welcome to GIS.SE. What do you mean by "if I switch the coordinates"? Which ones do you switch to which other, and how? – Erik Oct 17 '18 at 14:38
  • You probably changed the projection definition when you should have reprojected the coordinates. – user2856 Oct 18 '18 at 5:57
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It probably because when you "switch coordinates" you are attributing a new CRS instead of reprojecting (meaning the actual coordinate are not modified, you have just changed the name of the CRS)

So before the switch the on the fly reprojection was working and everything was overlapped, after the switch the on the fly reprojection "shut off" because all the CRS where assumed to be identical but as the coordinate are different there is no more overlap.

if you want to have all of your data in the same CRS you should reproject your data (use "reproject" (for vector) or "warp" (for raster) from the processing toolbox or right click on layer name then export>save as...)

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