Survey Coordinate System with Unknown Base Location

I plan on performing a survey using two Emlid RS2’s in an area with with no known control points or internet connection. Because I have no known control points to set up the Base and no NTRIP connection, I plan on getting the coordinates of the base using the "Average SINGLE’ coordinate entry method using an averaging time between 5 and 10 minutes. I also plan on logging the base location to run through OPUS to get the absolute coordinates.

If I’m using the Average SINGLE coordinate entry method for the base’s location, can I perform the survey in NAD83 State Plane or do I need to perform the survey in WGS84 because that is the datum the base is already in? I plan on shifting the entire survey in CAD based on the difference between the Average SINGLE solution and OPUS solution.

You should be able to average the point, convert it to NAD83, manually enter that as XYZ and then setup your project in Reachview 3 to use a SPCS. Once you have run it through OPUS they will give you a NAD83 equivalent by which you can shift your data. I have not personally used OPUS for an actual project because we just work in State Plane and align in CAD but we normally have a control point within a couple miles of the site. If you can find anything, even if that means setting up you base, shooting in a point closer to the site and traversing into the site that will work as well but if it’s not an NGS point you will need to know what coordinate system was used.

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Because I don’t have access to an online coordinate conversion tool, what do you suggest for converting from WGS84 to NAD83 in the field. Is it possible to do by hand or is there offline software that I could use?

I’ve been using this site. The are some true Surveyors on here that probably have some better tools but this gets what we need when we have to run a local base. Depending on where you are the coordinates might look almost identical but I always check it before I enter. Since you are planning on PPP your base it probably doesn’t really matter but I’ll let someone else confirm that.

This one is also good but only provided State Plane and UTM

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You can install this locally on your PC , handy tool


I have looked at this but just have not had the time to sit down and start training on it. Do you have any links to any documentation like that they might have?

It’s pretty straightforward, just install and follow the instructions provided. I installed the full package ( was rather large) . There is an option to just pick the coordinate systems you want if I recall, would probably make the install a little smaller.

Hi @Hydro_Jack,

Michael is right: it cannot be done without conversion. When Reach averages coordinates in the Base mode, they are in WGS84.

Other than that, I see no possible issues.


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