What coordinate system to export shapefiles
I understand the concept of working within a projection whenever in a map, rather than a geographic coordinate system. However, I notice that when ESRI provides data, it is in NAD_83. If I am working in a map and I create a shapefile, but I want to make it accessable for use by others and for other maps other than my State Plane map, do I work in a specfic projection, but export shapefiles into a geographic coordinate system?
Thanks for your help.
Mapping Center Answer:
As long as the coordinate system (i.e., projection) for the data you share is defined, then that is all that is required for someone else to be able to project and use your data correctly in ArcGIS.
There are advantages to leaving it in the coordinate system you are using -- for example, if someone wants to make measurements, the State Plane coordinate system is better than a geographic coordinate system (like NAD83). However, there are also some advantages to other projecitons. For example, if you wanted to share your data on the web for mashups, then the Web Mercator projection would be a better option. If you are not sure how people will want to use your data, then leaving it in the projection you are using is probably the safest thing to do since it will then have undergone the least amount of processing prior to redistribution. But be sure to define the projection, and you could also use the metadata to provide additional documentation.
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