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I'm trying to project some point data in ArcMap.

I created the point data in excel, then summarised it in R and exported it as a csv. Then added it through 'add XY data' tool in ArcMap, and exported it from an events file to a shapefile.

The points appear in the correct place, relative to each other, but when tried to overlay on the world imagery basemap, it simply sits down near Antarctica.

I've checked and re-checked the projections of the imported layer and the dataframe (I'd like to work in GDA_1994_MGA_Zone_56), but have also tried changing to a geographic coordinate system, which doesn't change anything. In fact, when I try to change the projection to a gcs, using the 'project - data management' tool, this error comes up.

invalid extent for output coordinate system
Failed to execute (Project).

I can't for the life of me figure out what is going wrong, there's probably a simple explanation, but I'm at my wits end!

Erica
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Alice Howie
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  • My latitudes and longitudes were stored as characters in R (not numeric)... would this potentially cause an issue? Initially I didn't think so, as the points are coming up positioned correctly relative to each other, just not in the right spot on the map... – Alice Howie Jun 18 '20 at 01:51

1 Answers1

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It helps to have them stored originally as numeric data, but since it's actually coming in as a CSV, I think they are importing as numeric -- as you note, they are correct relative to each other.

If your points are showing up on a map but in the wrong location, then their initial projection definition is incorrect. Looking at the Add XY Data dialog, you need to specify an initial coordinate system. If nothing is specified, ArcMap assumes that it is latitude/longitude decimal degrees.

Once it's imported as the wrong coordinate system, attempts to reproject will just continue the But you do not necessarily need to delete the points and start to re-import from scratch. Try using the Define Projection tool (which modifies the metadata to the desired projection) instead of Project (which mathematically recalculates coordinates from current projection to a new projection).

Erica
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