Base Station and NAD 83 Corrections

Ok coming from an environmental resource background I am somewhat new to the precision mapping world so please excuse my ignorance. My RTK corrections are coming over in NAD83. However I know my base station will only be recording raw data and getting the RTCM data from the correction service so I understand the coordinate system corrections in that regard don’t matter (or if they do please correct me). I will be using RTK to create my known base point out in the field on most missions. I have had nothing but issues with OPUS and have given up on that as a primary solution. Since I have NAD 83 corrections coming over I will have to collect that base point in NAD 83, but PC master requires a WGS 84 Lat/Long for processing. So my thought was, collect the base point in NAD 83 (Whatever UTM Zone Im in) with ellipsoidal height and just do a projection transformation in ArcGIS Pro on the back end to get the lat/long needed for PC Master from the point I collected in the field. I am pretty sure this workflow will work. Just wanted some thoughts. Thanks.

Look at it this way:

We live on a globe, which has Lats/Longs. Everywhere we are, there is a Lat/Long.

Knowing this, and the fact our planet is a spheroidal object, we simple humans make flat planes and assign that plane a coordinate. This “coordinate” could be any type of x,y,z coordinate. To keep navigation simple and precise, we have created massive coordinate systems. You will recognize “UTM” coordinates (UTM Zone 12N epsg32612) or something similar.

But I’m in NAD83… Ah yes, that is when the models were built. It’s “better” than NAD27. What makes it better? Its how we measured the globe. Its more refined. Gets better mileage and WORKS with our fancy GNSS toys. AND… no matter what coordinate you get, it WILL have a Lat/Long assigned to that exact point, no matter what.

So, how do you collect your base point? Was it supplied by the friendly neighbourhood surveyor? Did you occupy the point and use the data supplied by the base station? Did you…

—> So I arrive in the field. I place my base point (spike or target), shoot the point I wish to set my base station up on (in my chosen coordinate system).

  • I can create this point from the data supplied by my correction service (OPUS in US, Cannet in Canada)
  • I can occupy a known point, created by someone else. In this case, you can verify with your instruments and check the awesomeness…

Once you are happy, you start recording your GNSS against the point you created or occupied.

Now, once you are finished your flight, you wait and than stop your GNSS recording. You promptly fire up your PC Master and that window with the Lat/Long/ELLIPSOIDAL values. THIS is where knowing the EXACT location matters… as the file only reads the first line in the gnss file, you must enter the CORRECT coordinates.

  • you have this, because you either
    1: created the point… and your coordinate system WILL translate to a lat/long.
    2: the supplied point WILL translate to a lat/long.

If you can get your RTK point out in the field, great! If you go to a project with no survey, you must create that point or have someone do it for you.
Its all about that point when you calibrate your lidar data.

1 Like

I have got this figured out guys. Thanks in advance!

1 Like