[GIS] Overlay a Lat/Long CSV and NAD83 Shapefile in QGIS

coordinate systemcsvlatitude longitudeqgis

I have a shapefile/accompanying projection files etc:

CURRENT.prj
CURRENT.shx
CURRENT.shp
CURRENT.dbf
CURRENT.sbx
CURRENT.sbn

I also have a CSV of geocoded (lat/long) points.

I load up my lat long points using add delimited text layer save them using: use spatial index with X == longitude and y == latitude. I set the CRS as WGS 84. This loads up nicely and in the expected shape.

However, when I load my shapefile I no longer see my points and I only see the contents of my shapefile. My CURRENT.prj file shows:

PROJCS["NAD_1983_StatePlane_New_Jersey_FIPS_2900_Feet",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",492125.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-74.5],PARAMETER["Scale_Factor",0.9999],PARAMETER["Latitude_Of_Origin",38.83333333333334],UNIT["Foot_US",0.3048006096012192]]

If I look at the layer properties it's using NAD83 as its CRS.

It's not clear to me if the points are no lining up with my shapefile or are simply scaled to a size that isn't visible. I have tried several different CRS settings to no avail. How do I go about debugging this?

It actually just seems to depends what I load up first. If I load up my lat/long points I see those, if I load up my shapefile I see that instead. I never see the second thing I load. "Zoom to Layer" has no effect either way, I can only zoom to the first thing I loaded.

If I go "set project CRS from layer" I can then switch between "zooming" to my points or shapefile. Looks like they're just mapping to very different places (projecting isn't working)?

My shapefile's coordinates are in the 600k, 600k range, while my point coordinates are all in their lat/long (think -70, 40) so it definitely looks like it's not projecting correctly.

For reference I am new (as in a few hours of messing around) to GIS.

Best Answer

After you have added the shapefile, take a look at Rightclick -> SET CRS for Layer.

The layer CRS should be either EPSG:102711, or a custom CRS with these parameters:

+proj=tmerc +lat_0=38.83333333333334 +lon_0=-74.5 +k=0.9999 +x_0=150000 +y_0=0 +datum=NAD83 +units=us-ft +no_defs

You can enable on-the-fly-reprojection, set the project CRS to EPSG:3857, and add a Google or Openstreetmap background with the openlayers plugin. Then you can see which layer is placed well, and which is offset.

If not, it might well be that the .prj file CRS information is wrong, and the shapefile has another projection. It might help to report the extent of the layer, from Rightclick -> Properties, metadata tab.

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