[Qgis-user] Your Bearing Distance problem

[J.O.Williams]

A couple of years ago I had the same problem verifying some Bearing-Distance surveys by the US governments Mineral Surveyors. The land was patented back in the 1872 to 1900 time frame. The townships and sections even now have not been surveyed.  The south-west corner of Colorado was surveyed using the New Mexico State Plane coordinate system and was surveyed in from the south and not surveyed in from eastern Colorado.  When the original surveyors surveyed the "probable" sections, the sections were off by about 1/2 mile.  The error was discovered because I lined up a lake on the the original plat with a modern topo. The lake was off by the 1/2 mile from where the plat's section lines were supposed to be.  The mining claims were surveyed into well surveyed mineral location markers.

If the attachment gets stripped please email below and I will reply.

Hope this helps.

J.O. Williams

j . o . williams . jow @@@ gmail . com

The attached PDF is a white paper I wrote on how to verify a modern, year 2000+, GPS resurvey of the mining claims.  The resurvey was however was a partial resurvey.  Some of the claim corners were resurveyed using GPS, but the late 1800's  survey was very good. The other edges of the claim parcels could be re-plotted from the old patent plats. I wrote some code for QGIS 2.18 for bearings and calculated a distance from the US BLMs GLO shapefiles.  By running the calculation scripts, I could compare the "new" bearing-distance" with a georef'fed PNG of the claim survey plat.  The calculations were also run on the tie lines to the Mineral Location Markers. The biggest "gotcha" is getting the angle between the map quadrangles lat-long lines and the UTM coordinate lines.  The angle is available for the center of a topo sheet in the lower left hand corner.  That is the "Grid north rotation factor" discussed in Notes and or Problems number 2. At the time this code did what I wanted it to do.  There are problems with rounding such as "N 15-60 W" being reformatted to "N 16-0 W".

Re-Survey-Workflow.pdf
Description: Adobe PDF document

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