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I have a tract map delineating property lines using distances and bearings. It looks something like this (screenshot of part of it):

Portion of a Tract Map Showing Property Lines with Distances and Bearings Annotated

My goal is to locate the exact property corners of one of these lots using an RTK GPS rental.

To do so, I believe I need WGS84 coordinates. I do already have the coordinates of one of the quarter section corners referenced in the map (in NAD83), but not of the property corners I am interested in.

How do I accurately translate the bearings and distances from the tract map to WGS84 coordinates using QGIS?

My first idea was to use the "Advanced Digitizing" tool in QGIS, to "trace" the tract map, starting from the known quarter-section coordinate. However, I'm worried that I am losing accuracy since QGIS assumes some projection, whereas the measurements I have on the map are real-world distances. For example, when I put a line 300 ft north from the starting coordinate using "advanced digitizing", I'm not sure that those 300 ft on the map correspond to the correct distance on the ground.

Any advice?

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Determination of legal boundaries can only be legally done by a registered surveyor. I am not one, and neither are you, given the nature of your question. But if you want to do it for fun or so you have a rough idea (always acknowledging that your findings have no legal bearing and are probably not accurate) a general process might be:

  1. Use a CAD program to draw the lot boundaries and connection to any control marks that are relevant (usually want 2-3 control marks).
  2. Upload your drawing to the GPS controller.
  3. Go to the site, find the control marks/monuments, and use the GPS site calibration function to adjust your boundary file to local coordinates.
  4. Use the GPS to find the lot boundaries as desired.
  5. Get a surveyor to do it properly before you say anything silly to your neighbours.
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  • Thank you Glen. I definitely understand that I shouldn't make any legal conclusions (or neighbor confrontations) from an amateur survey. It's just to get a rough idea. I understand from your response that the coordinates are not usually "calculated" ahead of time; instead, a CAD drawing is georeferenced in the field on the GPS unit itself. Do you happen to know what file formats most GPS controllers expect? Would there be a way to get coordinates "offline" before going into the field beforehand as a backup? I'd like to be well-prepared before I go out and rent the tool.
    – anroesti
    Nov 28, 2023 at 21:23
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    Again, I am not a surveyor and am drawing on limited experience. Most controllers want dxf. Some coordinates may be calculated or downloaded (such as the coordinates of control marks) but no, the boundary corner coordinates are not determined beforehand. Everything is a vector, and everything must be related to previous plans and what's actually on the ground.
    – GlenS
    Nov 28, 2023 at 21:35
  • Thanks, really appreciate your insights.
    – anroesti
    Nov 28, 2023 at 21:49

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