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Custom Grid Coordinates?

February 20 2009 | 1 comment
Categories: Map Data

I have a know site that is in NAD_1927_StatePlane_California_III_FIPS_0403. Within this site our engineers created a grid that they used to mark locations that were of interest to them. For example there was a location of interest at (starting at the A0 grid line) -250', -50'. They asked me to plot these locations on the existing grid in my map layout. How do I do this? I am lost. I have attached a sample of the locations I am talking about.

Mapping Center Answer:

Wow that's painful. Your engineers did you no favors! 

I would do this by geocoding and then offsetting the results.  You will need to uniquely name each cell in the grid dataset, "A1", "A2", "A3",...  To do that add a CellName field and use the field calculator to with create a name based on Col_ID + RowID.  Then create a single field geocoder for the grid dataset.

Then in your input table you'll concatenate the first character of your X and Y.  You should also create Xoff and Yoff fields as well for the X and Y offsets.  Then create OldX, OldY, NewX and NewY fields (type = double)

Geocoding your table to your grid will produce points on the grid that will still need to be offset.  You'll want to start editing and select all these points and drag them such that they are located on the origin (xMin and yMin of each grid cell). Save the edits and stop editing

Now use the Calculate Geometry tool for the OldX and OldY fields (right click on the field heading in the table window).  Choose to store the X and Y coordinate in each of your fields.

Your coordinate system's (Cal SP III) units are in feet, so you can now us the field calculator to calculate the NewX and NewY fields with OldX + XOff = NewX  and  OldY + XOff = NewY. 

While your table window is open, choose Export from the Options menu. This will save a table.   Now use that table to generate an XY data layer using the NewX and NewY fields with the Add XY Data menu choice on the Tools menu.

Definitely check your work at this point to verify that the offsets moved the points in the proper direction--if not make the adjustment.

DSMapBook posted by Christopher Mathers on Feb 23 2009 8:10AM
If you have DSMapBook you can use the Create/Update Grid tool to make your grid and it will automatically name each cell using conventions it gives you options to set.

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