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I am a wildlife researcher and I am trying to create a set of points 1 km apart on a map of a particular area of my study region. I created a polygon (in Google Earth) that is about the size of what I need my study site to be over the study area, imported this into ArcMap and created a fishnet to the extent of the polygon (with the grid cells 1x1km).

With the fishnet function, evenly spaced points already come up, so what I want to do with those is extract the xy coordinates so I can put them into my GPS device and find them on the ground at my study site!

So, I followed instructions and extract values to each point and used my satellite image data layer of my map with my study site as the input raster; the geographic coordinate systems for all of my files are GCS_WGS_1984 and the projected coordinate system is WGS_1984_Costa_Rica_TM_90 (as my study site is in Costa Rica). I then did the add XY coordinates tool and entered the points shapefile I just created with the extracted raster values in the attribute table. However, the UTM coordinates I am given are way off my study site when I put them into Google Earth to check. I'm not really sure what is going on. I'm wondering if it is off because it is derived from the satellite image in the projected coordinate system rather than the geographic? Maybe it's skewed? Does anyone know how I might be able to fix this mismatch?

I would just use Google Earth but the point function in ArcMap is critical to spacing out my sampling sites correctly. I decided to test some other GPS coordinates I had added to ArcMap as XY data and they too were very off in Google Earth when put into UTM in ArcMap.

For example, one point in ArcMap was: 412327.28387 M E 1136639.13284 M N and the same point in Google Earth was: 741099.72 m E 1137197.38 m N

However, one other thing is I do not know what the UTM zone is; Google Earth said 16 P, but ArcMap does not specify.

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There are several similar versions to the Universal Transverse Mercator system. Google maps, including Google Earth, are using the "WGS 84 / Pseudo-Mercator" coordinates projection. It's not the same as "WGS_1984_Costa_Rica_TM_90" you are using.

You should change the file coordinate, if you are uploading files to Google Earth you need to change the coordinate system into "WGS 84 / Pseudo-Mercator" and if you are uploading files from Google into your maps you need to change there coordinate into "WGS_1984_Costa_Rica_TM_90".

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    Thank you so much! I guess my biggest concern is making sure that when I add these UTM coordinates to my garmin gps device, it will find the correct locations on the ground. The garminn position format is UTM UPS and the Map Datum is WGS 84. Do you know which version of the Transverse Mercator system would be appropriate for this use? Thanks again!
    – Jordan
    Commented May 24, 2017 at 14:15
  • Hi, if this helpful Please give me mark the answer as "answer" or if the answer in part mark the red triple for a good answer. If the map Datum is WGS 84 you should transfer the files CRS into WGS 84 as well. In general, the file CRS should always be sure that the file CRS is accurately like the map CRS.
    – Nitzan Matan
    Commented May 25, 2017 at 9:29

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