GCPs coordinate system and geoid

Not sure where to put this in the forum but I received these questions from our data engineering and was wondering if someone could provide insight here? Thank you!

  1. Look for options in settings for setting the coordinate system that the GCP’s are captured in
    1. Look for options in the settings for the GEOID that the GCP’s are captured/processed in

Hi Thomas,

You can set the coordinate system and geoid in ReachView 3. You can check our guide to learn which coordinate systems and vertical datums are supported by the app.


Similar topic. In ReachView 3 app, when creating a new survey project, the default coordinate system is “Global CS”. Is “Global CS” the same as WGS_1984 EPSG:4326?

Hi Chris,

Welcome to our community forum!

The rover’s coordinates always depend on the base datum. If it’s in WGS1984, the rover will have non-projected geographic coordinates in WGS1984. For instance, if the base datum is in NAD83, the rover’s coordinates will be in NAD83.

Simply speaking, the Global CS option is applied when you don’t need to convert geographic coordinates into the local projected ones. But they will be in the same datum as the base is.



I must repeat Chris’ question: what is Global CS exactly?
As I understand, if you do the survey in the reach panel (which is where I did mine), you don’t get to pick the coordinate system.

I need to convert the survey I did but I can’t figure what is this Global CS (and it’s datum).

The coordinate system and datum that you key in at the base will be the same system at the rover. That is the case whether you are using RV3 or just reach panel. With reach panel, it will only be a Global Coordinate System (GS) in lat/long as opposed to a local coordinate system option. If what you are asking is what system is the Global CS in reach panel/RV3, it’s simply WGS1984. I find this site to be a great resource, at least in North America….ITRF2014, WGS84 and NAD83 | GEOG 862: GPS and GNSS for Geospatial Professionals


All right, so if the Glocal CS is used, the elevation (Z) is only ellipsoidal. I would still need to post-processed the coordinate in order to get an actual mean-sea level elevation.

I will test the precision of doing a survey directly in a local projected system but I am curious to know if others have already done it and how does it compare in terms of precision. Because the app needs to apply a tranformation in order to shift the basic WGS84 coordinates in input to the chosen local system, and, from my experience, there can many transformation equations.

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Hi Anne-Marie,

You can get centimeter-accurate coordinates with local coordinate systems and vertical datums in ReachView 3. As I know, most of our users work in their local coordinate systems. So, I’d really recommend trying it out – it’s the most straightforward way to get projected coordinates and orthometric heights.

When you choose a local coordinate system in ReachView 3, you’ll see a note about the required base datum. In most cases, the projection is applied right to the base’s datum, so there are no datum transformations in-between.

As for the Global CS option, it’s pretty similar to how Reach Panel works. No transformations or projections are applied. As Zach said, it means that the rover’s coordinates will be in the base’s datum. This datum is not necessarily WGS84 – if you enter the base’s coordinates in NAD83, you can collect NAD83 points with the rover. And you’re right that with the Global CS, only ellipsoidal heights are available.