I was wondering if I import shapefiles with unknown spatial reference into a feature dataset, with desired coordinate system, would that work?

  • Bad things could happen. If your shapefiles do not have a spatial reference one of three things will occur: 1 fail to import, 2 import and adopt the spatial reference of the dataset, 3 assume geographic/projected as WGS/NAD and project accordingly. Please take the time to define your shapefiles spatial reference before importing. – Michael Stimson Jul 15 '15 at 1:27
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    Actually, with a feature dataset, you'll always get the FDS's coordinate reference, despite any explicit request otherwise. Still, it's better to always correctly define the projection of all shapefiles. – Vince Jul 15 '15 at 1:34
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    Why wonder when you can test and examine the results? I think this should be done prior to asking a question like this one. – PolyGeo Jul 15 '15 at 2:02
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    Based on a quick test, a shapefile in a projected coordinate system (PCS) without a defined projection will import into a feature dataset with a PCS, however, the resulting feature class will be corrupt. On the other hand, a shapefile with a geographic coordinate system will import into a feature dataset and display properly. It is always best practice to make sure your spatial data have defined coordinate systems prior to import into a FGDB. – Aaron Jul 15 '15 at 2:40
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    @AliKhatibi Defining the coordinate system is very fast and efficient in ArcGIS. You can automate the process in ModelBuilder or with Python. – Aaron Jul 15 '15 at 12:08

No, it will not work (unless you're just using the import to define the CRS to what you know it is supposed to be). When importing to a feature dataset, everything must end up in the same CRS. The import process can automatically project from the source CRS to the feature dataset's, but in order to do that it has to know the source CRS in the first place. If it doesn't, because it's defined incorrectly or not at all, it will essentially define the source as target and make no projection. This is just like using the Define tool and setting it to whatever.

If you have an undefined coordinate system, you must properly identify it first and then define it before the software will be able to do anything with it automatically (at least, correctly). It can't project if it doesn't know what it's projecting from, or it will give you bad coordinates if you tell it to project from something incorrect (which is even worse than just defining it incorrectly since you'd be transforming values).

If you know what CRS they should be in, it sounds like you're just looking for a way to batch project, as described at Defining projections for multiple shapefiles in ArcMap? If you don't know, or they differ, you're going to have to investigate them all individually.

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