GIS update - transforming coordinate systems

Following on from a previous post about getting my data files ready to use in my model, I need to update the transform coordinates instructions.

I previously stated that this could be done effectively from within ArcMap. However I have been having problems getting this to work correctly through the transform command within ArcMap (View - Data Frame Properties - Coordinate System - Transformations).

Some of the data I have been provided with has an underlying coordinate system of WGS_1984_UTM_Zone_16N, but camera data I have has been supplied in NAD_1927_UTM_Zone_16N and so my data files need converting to the later coordinate system.

There is a difference between the Geographic Coordinate System and the Projected Coordinate System. The supplied WGS_1984 is from the Geographic Coordinate System and transforming this only allows you access to other Geographic Coordinate Systems. The correct NAD1927 coordinate system is not geographic but projected and so the transformation function within ArcMap does not adequately transform the data....

so... this can be done more effectively from within ArcCatalog...

Navigate to the appropriate file in ArcCatalog, i'll run through this for my data layer of rivers

1. Select modelRivers.shp
2. Click on File - Properties
3. Select XY Coordinate
4. Choose Select
5. Chose Projected Coordinate Systems - UTM - NAD 1927 - NAD 1927 UTM Zone 16N.prj
6. Click Add
7. Click Apply - OK

Note, you cannot change the coordinate system if the file is already open in ArcMap, so you need to remove the layer from ArcMap before attempting to change the coordinate system.