I have an RS3 and will be shooting points for a project in Puerto Rico on the east end of the island. They already have points shot on a Carlson/Stonex GPS setup that has a vertical file indicated as “Puerto Rico 2012b.gsf”. I feel I’m pretty safe assuming this is Geoid12b, but know that there’s apparently a difference in NAVD88 vs PRVD02 for that area. I also noticed a note in the changelogs for 5.2:
" Added
We added new vertical CRSs to support the legacy “GEOID12B” geoid. It covers the CONUS area and Alaska “NAVD88(GEOID12B) height”, Virgin Island “VIVD09(GEOID12B) height” and Puerto Rico “PRVD02(GEOID12B) height”."
However, when setting up the project in the Emlid app, I’m just seeing
-NAVD88(GEOID12B)
-NAVD88(GEOID18)
-NAVD88(GEOID18) Puerto Rico
-and a few other non-relevant datums.
My question is: what would be the best vertical datum to select to ‘marry up’ best with the other GPS’ data?
One way would be to collect your points with ellipsoid elevation and then use the NGS Geoid 12B tool to get a geoid undulation for each point.
Then use the formula H = h -N to obtain your orthometric elevation.
H = orthometric elevatio (What you want)
h = ellipsoid elevation (what you measured on the point)
N = Geoid undulation (What you got from the Geoid 12B tool).
You’re right that “Puerto Rico 2012b.gsf” is a version of the GEOID12B geoid model, specifically for Puerto Rico. While NOAA uses the same name (GEOID12B), they have separate files for different regions. To make sure your vertical datum aligns with the other GPS data, it’s important to confirm the exact geoid model that’s being used.
Right now, we have the latest geoid for Puerto Rico, which is NAVD88 (GEOID18) Puerto Rico height. This will give you orthometric heights consistent with the Puerto Rico Vertical Datum of 2002 (PRVD02).
Thanks, as it appears Puerto Rico 12b is no longer available for the Emlid so we’ll use geoid 18. Using the NOAA geoid calculators, it appears in that part of the world there is a difference of roughly 1.8cm in elevation change between the two so I can handle that just fine.
Yep, that’s correct. The GEOID12B Puerto Rico model isn’t available now. Version 5.2 is a bit outdated, but we do support the Puerto Rico PRVD02 height. The geoid just has since been updated, and the latest version is GEOID18. This model ties NAD83(2011) ellipsoid heights directly to PRVD02 in Puerto Rico. Hope it works well for your needs!
