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I feel like there has to be a good way to do this in ArcGIS but can't seem to find it. I have well survey's that pinpoint well locations using the FSL (From southern line of section)/FWL (From western line of section) convention. These descriptions are essentially coordinate pairs but I can't seem to find a good way to accurately use them in ArcGIS. I can use the measure tool and get a good estimate, but I would love to have a way to specify the BLM section and then enter the FSL/FWL and pinpoint the well. Does anyone have any ideas of how to do this?

  • I've done a tag correction here, but you might be referring to a 'section' that is specific to oil/gas/mineral mapping rather than what the term usually means (and note the BLM maintains the PLSS); please do to correct it back (and maybe link to the sections you're talking about) if so. You don't really have coordinate pairs, you have relative coordinates or offsets. You'd need a section grid to reference, and then look at offsets as juturna mentions. However this might be a bit complicated depending on how precise you need to be, since the PLSS isn't a perfectly square grid. – Chris W May 27 '15 at 17:38
  • The most precise method I can think of would be to take an 'official' copy of the section grid, convert it to lines, attribute said lines so they have a NESW designator on them in addition to the TRS they should already have (and delete all east/north lines if you wanted), then for each point select the appropriate TRS line and offset it the given distance, then create a point where the offset lines intersect. I have no idea how to code that. – Chris W May 27 '15 at 18:53
  • @ChrisW I am refferring to BLM Twp/Rng, Sections. You are correct about these not really being coordinate pairs, they are offsets from the section lines done by survey crews. Of course the easiest but least accurate means of doing this is as juturna mentioned but with the non-perfect grid I would start to see errors upwards of more than what I would like. I was able to come up with a couple ways to do this with a high degree of accuracy that I will explain in an answer, but these methods still feel like work-arounds. – GeoJohn May 28 '15 at 16:32
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I was able to come up with an accurate means of achieving my desired results by creating a line FC with two features. One that follows the Southern line of the section polygon and another that follows the Western line of the section polygon. Using the offsets given by the survey, I put buffers around each line with the corresponding survey offsets and then was able to pinpoint my location based on the intersect of the buffers.

  • I hadn't thought about using a buffer, which is potentially a better method than trying to use a COGO offset (particularly given licensing restrictions); though one would have to be careful with coordinate systems (and Cartesian vs geodedic buffers). I wouldn't really consider that method to be a work around, short of writing a dedicated script or model that takes the TRS and offsets in as parameters and does everything else for you. You might be able to make some refinements, but since they're relative references at some point you have to work with the lines they reference. – Chris W May 28 '15 at 20:43
  • Good point, I didn't consider the effect that Cartesian or Geodedic buffers would induce. I think I will try to script this and see what happens. – GeoJohn May 29 '15 at 13:25
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This may not be the quickest way to solve the problem, but if these coordinates are relative to the BLM section, you could place them at the BLM section and then move each point individually using basic editor tools in ArcMap (see: http://resources.arcgis.com/en/help/main/10.1/index.html#/relative_to_its_current_location_delta_x_y/01m80000002t000000/).

This could be done programmatically in ArcPy using the SHAPE@XY token that came with arcpy.da.UpdateCursor. See the answers to this question.

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