QGIS 1.8.0 - Define shapefile as UTM 15 NAD83 Feet

Question

I have a shapefile which the .prj file says it is

PROJCS["NAD_1983_UTM_Zone_15N",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",1640416.666666667],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-93.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Foot_US",0.3048006096012192]]

QGIS's on the fly reprojecting is not working. It has worked well enough for me so far but I can't seem to figure out how to change the UTM to feet from meters.

Answer 1

UTM is always in metres, being internationally standardized. The proj string for UTM 15N is:

+proj=utm +zone=15 +datum=WGS84 +units=m +no_defs

So if your data is in feet, create a custom CRS with this string:

+proj=utm +zone=15 +datum=WGS84 +units=us-ft +no_defs

or look for the NAD83 projections of the US state your data is about.

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EDIT: To add a custom CRS:

• Settings -> Custom CRS

• Click on the yellow star to create a new CRS

• Enter a name, like UTM15 ft

• paste the proj string in the second line

• Click on the save button