Stake Out NAD27 State Plane Coordinates

Emlid Flow & Emlid Flow 360 Coordinate Systems
22

Hi Mark,

No worries, you can test this at your convenience. I was just curious to know how it goes :slightly_smiling_face:

As for the points mismatches, I discussed this with the team. We suppose the difference in QGIS may be caused by the inaccuracy of the transformation that QGIS uses for NAD27 points. And so I believe that the points should be in the right place when staking out.

23

Thanks.

I have set up the base with the latitude and longitude from the section corner tie sheet.

It looks like the only option for entering the location for the base station is using decimal degrees for latitude and longitude. Is this correct? I did not see an option for entering state plane coordinates for the base station.

The rover is set up using the NAD27 state plane coordinates in feet for the central Utah zone.

24

Hi Mark,

The rover expects the base will transmit its position in a geographic CS based on the same datum as the CS of the rover. So, if you’re going to work with points in NAD27, you need to convert your base projected coordinates into NAD27 geographic coordinates. Then, you can enter them in the Base mode tab manually.

25

So I hope I understand what you are saying. You do not change the datum in the base. The latitude and longitude need to be based on the datum that your rover is using. In this project the stake out points are in NAD 27 (ESPG 32043) State Plane Coordinate System, Utah Central in feet.

To set up the base I will need to project the NAD 27 SPC Utah Central feet coordinates of the section corner to decimal degrees latitude / longitude using the ESPG 32043 datum. I think this can be done in Corpscon6.

Is this what I need to do? Is there a better method?

26

Hi Mark,

Hmm, it seems right. In your case, you need:

  • For the base, convert the section corner coordinates from NAD27 / Utah Central (EPSG:32043) to NAD27 geographic decimal degrees (latitude/longitude/ellipsoidal height) and enter them in the Base mode tab
  • For the rover, create a project in NAD27 / Utah Central (EPSG:32043) and import your points

Let me know when you test it!

28

I went out Saturday and set up the base and rover. The base was on a known point and its location coordinates in NAD 27. I took the rover to the survey site and checked out the NAD 27 points. Though the points were not being displayed correctly on the base map they were in the correct real world location. So as you suggested the emlid receivers are providing the correct location and the rendering of the base map is incorrect.

Thank you for your help.

1 Like
30

Hi Mark,

Good to know you’ve got accurate coordinates! Thanks for keeping us in the loop :relieved:

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