I am using ArcGIS 10.1 (SP1). I got a shapefile with polygons representing some features of the landscape in my study area. This file has been provided by a third party institution.
The coordinate system is missing spatial reference, as ArcGIS informs me as soon as I feed the file into ArcMap. I tried to use 'Define Projection' tool, but nothing happens, i.e. when I add other feature classes created by me (and that matches one another) the shapefile into question does not 'match' the rest of the layers.
Upon further inspections, I realized something that puzzles me even more. I am seeing that, if I take into account a given point in the map, its coordinates correspond to the actual coordinates in the right coordinate system (namely, ED1950 UTM Zone 33N) but are stripped of the first couple of digits. For example: 'true' coordinates of a point 439811 / 3986516, corresponding coordinates in the problematic shapefile 39811 / 86516; so, the first is missing the first digit, the second is missing the first two.
I would like to know if there is any way to fix this problem?
What I seem to understand for sure is that ArcGIS does not recognize this insane 'stripped' version of the ED1950 UTM Zone 33N.
Best Answer
I'm going to put this as an answer, but I'm making several assumptions so this may not be the 'right' answer! This will prove whether or not the values are ED1950 UTM 33 North but with the leading digits stripped off.
Delete any coordinate reference system from the problematic shapefile. A very easy way to do this is to delete (or rename) the .prj file.
Add the shapefile and your reference data to ArcMap.
Make sure the data frame's coordinate system to ED1950 UTM zone 33 North.
Modify or edit it by changing the following projection parameters: a. Set the false easting value to 100000 m b. Set the false northing value to -3900000 m c. Also change the name; add _mod or something.
Okay all dialogs.
If this is the correct coordinate system, the reference data will be projected on-the-fly (in-memory) and line up with the shapefile.
If it works, export out the shapefile (right-click it in the table of contents) and select use data frame's coordinate system.
However, as other commenters have mentioned, it's possible this data is in a completely different coordinate system. (should be a comment) Can you tell us what country the data falls in, and/or from what agency you got it?
Note: The define projection or changing the coordinate system via the data's property page in ArcCatalog updates the metadata only. These workflows don't change the data's coordinate values nor extent, so the data has to be already in the coordinate system you're setting.