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I need to measure the distance (with the ruler) of points from two different layers. One layer is NAD83 and the other is NAD27. When importing the NAD27 csv file, I specified it was NAD27. Then I used: Toolbox-> Data Management -> Projections and Transformations -> Project and I projected from the input coordinate system of NAD27 to the output coordinate system of NAD83.

The issue is that I have a ton of CSV files, each with data from different projections (there is a column that specifies projection). I use Microsoft Access to connect a lot of tables and then extract the data I need, save in a table, and import to ArcGIS. The problem is that after I just transformed my NAD27 to NAD83, the lat/long in the actual table is still the same, so if I join the tables and extract data later on, I will have to do the transformations all over again.

Any advice?

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Try using the Field Calculator to recalculate the Lat/Long once you've done the data transformation.

If you need to preserve the original values (for some reason), then add two new columns and calc those with the NAD83 values.

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    There also a tool, Add XY Coordinates. – mkennedy Nov 14 '14 at 18:22
  • You both gave great advice. I found the tool for "Add XY Coordinates (Data Management)." I ended up using that but also did a quick practice with the Field Calculator, in case I go that route in the future. Thanks! – WolverineTime Nov 14 '14 at 19:53
  • @WolverineTime - YW. mkennedy's suggestion is faster/better for most applications. I should've mentioned it for a more complete answer. NOTE: Using the Field Calculator allows one to customize the field "values" and the Add XY Coords tool does not. Also using the tool may overwrite existing values - which can be good if you want it and quite bad if you don't. – user23715 Nov 14 '14 at 20:56
  • Hi user23715, I appreciate your suggestion of using the Field Calculator. Alas, I am still at a level in which I do not know what to actually input in the field calculator, so that it outputs the newly transformed lat/long. – WolverineTime Nov 18 '14 at 18:18
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    @WolverineTime The answer is a bit confusing in that you don't access the Field Calculator per se. To add XY coordinates you actually Calculate Geometry (another choice when you right-click a column heading in an attribute table). – Chris W Nov 24 '14 at 23:15

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