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Adding shapefiles in a different coordinate syste,

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02-10-2017 01:37 PM
SaraCrayton
New Contributor

Hello everyone.

I'm pretty new to using GIS. I'm building a map on top of the imagery basemap provided with ArcMap. When I went to add my first layers, a warning popped up with the titles "Geographic Systems Warning." It says "The following data sources use a geographic coordinate system that is different from the one used by the data frame you are adding into." My layer is in GCS_North_American_1983. I understand that I need to transform the data. When I click the transformations tab, it seems like my option is to transfrom from GCS_North_American_1983 to GCS_WGS_1984. 

My question is: there is a drop down box that says "Using." It seems to give options of ways to transform the data. The defualt option is "none." Is it best for me to choose one of these options or for me to choose none?

Thanks!coordinate systems and transformations #adding data

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3 Replies
AdrianWelsh
MVP Honored Contributor

Sara,

That warning is just a warning. If you're building off of a basemap, the Esri ones are typically projected in a WGS 84 Web Mercator projection. Therefore, I would think your layer should be in that same projection. If not, then GIS will reproject the layer on the fly and give you that warning each time. (info on this: About editing data in a different projection (projecting on the fly)—Help | ArcGIS for Desktop )

If you need your data to be in a certain projection or to assign a projection to it, use the Project tool from the toolbox:

Project—Help | ArcGIS for Desktop 

Also, this thread would be better served if placed in the https://community.esri.com/groups/coordinate-reference-systems?sr=search&searchId=653c1c39-1442-4dd6...‌ or https://community.esri.com/groups/map-projections?sr=search&searchId=b87c4658-3f43-4175-86b2-f8a7eb7...‌ groups.

JayantaPoddar
MVP Esteemed Contributor

You could use <ArcGIS Install Directory>\Desktop10.3\Documentation/geographic_transformations.pdf to choose the appropriate transformation method, depending on the datums and area of use.

The Esri Basemaps are in WGS_1984_Web_Mercator_Auxiliary_Sphere (D_WGS_1984). When adding data of GCS_NAD_1983, you could use transformation method GCS_North_American_1983 to GCS_WGS_1984.

Note: The Transformation method works both ways. GCS_North_American_1983 to GCS_WGS_1984 transformation method can be used when transforming from D_WGS_1984 to D_NAD_1983 and vice-versa.



Think Location
JayJohnson2
Occasional Contributor

This article spells out how to choose from the options list when using this transformation.  Essentially, it depends on where your data is located: https://blogs.esri.com/esri/arcgis/2009/05/06/about-geographic-transformations-and-how-to-choose-the...