Define projection changes position of raster layer

[DitlevReventlow]

Hey Everyone.

I use define projection on a raster layer that has the spatial reference system User_defined equidistant_Cylindrical and the datum user_defined, and change it into either equidistant_culindrical (Sphere) or equidistant cylindrical (world).

I try to do it into both because I am not sure which of them is the correct one. My thought was then to convert into WGS_1984 afterwards and see which fits best.

However, when I do the define projection, the whole raster drastically changes position. How can this be? Isn't define projection just used to define the projection system, not actually changing the position or drawing. This is at least how it has normally worked for me.

The reason why I am doing this is because I want the data in WGS_1984. Any help on how I could do this is also needed.

I would very much appreciate any help. Thank you very much!

Best regards

Ditlev Reventlow

[DanPatterson_Retired]

Melita....upon your review of the pre-existing threads, is there anything that hasnt been covered or suggested, except for the confirmation that one, or both has been defined incorrectly?  Perhaps the data should be zipped and posted or sent to esri to unravel this protracted issue. 

It would be useful to just remove the projection information (if it is in a format that this can be readily done, like a tif), then follow the procedure of adding each one to a separate data frame with no defined coordinate system...no other data ... and then introduce a basemap or to see what is going on.  There is an underlying assumption that one and/or both will line up with something.

[XanderBakker]

In addition to what Dan Patterson explained... the projection is used to interpret the coordinates of the dataset and define the location of the data on the earth. If you look closer to the variables that define the projection you will notice that the falseOriginAndUnits is different for both projections:

Sphere_Equidistant_Cylindrical	World_Equidistant_Cylindrical
-10007700 -10007700 10000	-10018900 -10018900 10000

This would mean a shift of 11200 meter in both X and Y

Python snippet:

import arcpy
sr1 = arcpy.SpatialReference(53002) # Sphere_Equidistant_Cylindrical
sr2 = arcpy.SpatialReference(54002) # World_Equidistant_Cylindrical
print sr1.name, "\t", sr2.name
print sr1.falseOriginAndUnits, "\t", sr2.falseOriginAndUnits