I have two datasets representing the same area in Romania, but in different CRS, A is local, B is WGS 84.

dataset A with:

Stereo_70 Authority: Custom

Projection: Double_Stereographic False_Easting: 500000,0 False_Northing: 500000,0 Longitude_Of_Origin: 25,0 Scale_Factor: 0,99975 Latitude_Of_Origin: 46,0 Linear Unit: Meter (1,0)

Geographic Coordinate System: GCS_Dealul_Piscului_1970 Angular Unit: Degree (0,0174532925199433) Prime Meridian: Greenwich (0,0) Datum: D_Dealul_Piscului_1970 Spheroid: Krasovsky_1940 Semimajor Axis: 6378245,0 Semiminor Axis: 6356863,018773047 Inverse Flattening: 298,3

and dataset B with:

WGS 84 WKID: 4326 Authority: EPSG

Angular Unit: degree (0,0174532925199433) Prime Meridian: Greenwich (0,0) Datum: WGS_1984 Spheroid: WGS 84 Semimajor Axis: 6378137,0 Semiminor Axis: 6356752,314245179 Inverse Flattening: 298,257223563

In order to convert B to A, I imported A's CRS to B=> Datasets did not overlap, they are miles away from each other.

Could anyone explain what exactly is the problem?

1 Answer 1


To convert a feature class with coordinate system B to a feature class with coordinate system B you can use several approaches.

One possibility is to use Project (Data Management) . You have to specify a datum transformation in this tool too.

Another way is: Add feature class A to a new data frame. Then add feature class B. Set datum transformation in data frame properties. Now both feature classes should align so that you can work with both feature classes. If you want to create a new feature class: Right click to layer B and export it to a new feature class.

  • checked first possibility before; didn't work. tried second: Added feature class A to a new data frame. Then added feature class B. Set datum transformation in data frame properties. feature classes didn't align:(
    – Ligia
    Commented Feb 20, 2013 at 11:18
  • 1
    When adding data A to ArcMap, ArcMap reads the coordinate system information stored with data A. The data frame use coordinate system A. If you add data B to the same data frame ArcMap will project data B 'on-the-fly' to the coordinate system that is set for the data frame (A). If the proper datum transformation is not specified you will see a misalginment of about 50 to 500 meters. If the coordinate system definition of A or B is incorrect you will see a very large misalginment (up to thousands of kilometers). So I assume: the coordinate system definition of A and/or B is incorrect.
    – Jens
    Commented Feb 20, 2013 at 11:46
  • This is exactly what I was writing now :) I think the coordinate system for B be is defined incorrectly. what do I do in this case?
    – Ligia
    Commented Feb 20, 2013 at 12:08
  • Do you know the corret coordinate system for B? Then use the tool Define Projection (Data Management) to overwrite the coordinate system information of B.
    – Jens
    Commented Feb 20, 2013 at 13:03
  • 1
    to 1: I think your original problem is solved: A and B have a misalginment of 0 meters to 50 meteres because of bad digitization. to 2: I suspect that the datum transformation from A to Bing and from B to Bing is not correct. To solve this problem I would start a new question on gis.stackexchange.
    – Jens
    Commented Feb 21, 2013 at 7:49

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