[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.

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".

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

Hope this helps.

J.O. Williams

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


-------------- next part --------------
A non-text attachment was scrubbed...
Name: Re-Survey-Workflow.pdf
Type: application/pdf
Size: 33742 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20210410/bba70815/attachment.pdf>