Repair Lat/Long Coordinate Errors on the Fly

Every once in a while, someone misses a step in processing raw lat/long coordinates. Sometimes data was transferred incorrectly, sometimes the data wasn't available.

Here's some data I threw together as an example - these are my favorite caving diving sites in Florida:

ID	Name	Latitude	Longitude
1	Jackson Blue	30.790475	-85.140083
2	Madison Blue	30.480518	83.244421
3	Orange Grove	30.127215	-83.13053
4	Peacock	30.122503	-83.1324
5	Little River	29.996677	-82.966328
6	Devil's Eye	29.83509	-82.69659
7	Devil's Ear	29.835297	-82.696568
8	Ginnie Spring	29.836178	-82.700148

Initial projection of data is missing a location

Something's wrong. I expected to see Madison Blue just north of that group of three points. (some of those spots are springs that are within a few hundred yards of each other.

! When projecting data, immediately zoom to that layer, or hit the Full Extent button  to ensure that all points were plotted properly.

ArcMap's Zoom to Full Extent tool

After I zoomed to the full extent of the data, I realized what must be wrong with the data (see below). Obviously there's a Longitude value that's missing its negative sign because I haven't been diving in India/Tibet before.

Zoom to full extent to check for mis-projected data.

A few quick tips:

• Locations on the same latitude, but on the other side of the world are probably missing or adding a negative sign
• Points off the coast of Nigeria/Ghana/Gabon, down under of Africa's west coast are probably inheriting a Null or erroneous value, so they're defaulting to the coordinate (0, 0).

• After zooming to the full extent of a map, use the Select Features tool to select those incorrect locations. In the Attribute Table, choose Show selected Records to take a look at the incorrect data.

Fix the Data

1. Start an Edit Session on that layer in question
2. Select the erroneous site. Mine is ID = 2, or Name = Madison Blue
3. From the Editor toolbar, choose the Sketch Properties button to open the Edit Sketch Properties window
4. Add a negative in front of the selected X value and press Enter or click Finish Sketch to apply the update

5. Save and Stop Editing

That's it! Piece of cake..

Corrected data plot