ESRI Basemap Coordinate Systems

[ManikMohandas]

I am trying to add shapefiles (lines) to the mxd file with the ESRI World Street Map as basemap. I get an error "Geographic Coordinate Systems Warning" The following data sources use a geographic coordinate system that is different from the one used by the data frame you are adding the data into"

I noticed that I get this error only when I add a line shape file and not when I add point shape file. Besides, both the line and point shape file have the same projections and coordinate systems when I checked it through the ESRI catalog.

Would appreciate any thoughts as to why I keep getting this error message.

[DavidBlanchard · Accepted solution]

The map document will get the Coordinate System of the first layer added. If you add the Esri World Street Basemap, this will set the document to "WGS 1984 Web Mercator (auxiliary sphere)".

If the data you add is not in the exact same coordinate system, you may be warned of this since accuracy may be reduced when projecting on the fly. If you are using low-accuracy data or simply visualizing the data, you probably don't need to worry. If you need higher-accuracy, then you can:

• Project the data
• Set the data frame to the data's projection (this will warp the basemap)
• Set a transformation in the data frame properties (if applicable)

As to why you only get the error message once, ArcMap will only warn you once when you add data of a different projection. The second dataset you add will not always generate a warning.

[ManikMohandas]

Thanks for your answer. I adopted your solution of setting the data frame projections and it worked.

When I just ignore the warning, I would see a red exclamation mark against the basemap in TOC and won't see any basemap being displayed. After setting the data frame projections to match with the shapefiles, I am able to see the basemap displayed correctly. Presently, I am not that much worried about the accuracy.