QGIS – Mysterious Lat Long Conversion to XY Problem in QGIS

coordinate systemlatitude longitudeqgis

I am trying to import a CSV file with Lat Long values I geocoded in Google Earth into QGIS, and I'm getting some very strange results.

A well-formatted decimal-degree Lat/Long pair (like 30.402716, -88.867475) gets translated into a tiny tiny XY pair like (-0.0008,0.0003). The points show up basically in the right position relative to each other, but these decimal values are way off relative to my other layers, why is this decimal conversion happening and why is it so wrong?

I'm using the "Create Layer from Delimited Text" dialogue, and I set X to Long, and Y to Lat, and selected the CRS to Google Maps Global Mercator EPSG:900913

Best Answer

If they're truly lat/lon coordinates, set the CRS to EPSG:4326 and see if that helps. If you want EPSG:900913, you'll need to ("re")project them.

Related Solutions

[GIS] Displaying lat long values from XLS in ArcGIS Desktop

When someone says that data points are tiny compared to other data layers, the usual problem is that the new points have been assigned a projected coordinate system--probably the one that the other layers are using--but the new points are latitude-longitude and should be assigned a geographic coordinate system.

The Add XY tool will default to the data frame's coordinate system. You need to change that to match what these points are in.

Even though you're seeing latitude-longitude in the data frame, the display units (data frame properties, general tab) may have been set to show degrees or degrees-minutes-seconds even though the data frame's coordinate system is projected.

Google Maps/ArcMap – Working with Lat/Long Coordinates

Due to various vagaries in the ArcGIS software, I'm going to tell you to use different coordinate reference systems. That will let you access the predefined transformations and hopefully make your life easier.

Use WGS_1984_Web_Mercator_Auxiliary_Sphere instead. This one uses WGS 1984 for the geographic CRS (aka datum). The one you're using, WGS_1984_Web_Mercator, uses a sphere (GCS_WGS_1984_Major_Auxiliary_Sphere) and there are no predefined transformations for it.

Next, use Monte_Mario_Italy_1 which is the same, just a different name. Pick Monte_Mario_To_WGS_1984_4 for the transformation.

Or if you want to use Roma_1940_Gauss_Boaga_Ovest, you'll have to define a custom transformation that's a copy of Monte_Mario_To_WGS_1984_4.

FROM roma 1940 TO wgs84
Method: Position Vector
X axis translation: -104.1
Y axis translation: -49.1
Z axis translation: -9.9
X axis rotation: 0.971
Y axis rotation: -2.917
Z axis rotation: 0.714
scale difference: -11.68

If you define a custom transformation in ArcMap, you may have to define it FROM wgs84 TO roma 1940. If so, change the signs on all parameters.

Best Answer

Related Solutions

[GIS] Displaying lat long values from XLS in ArcGIS Desktop

Google Maps/ArcMap – Working with Lat/Long Coordinates

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