[GRASS-user] Working with USA Public Land Survey System

[Matthew Perry]

On 8/31/06, Dylan Beaudette <dylan.beaudette at gmail.com> wrote:
> On Wednesday 30 August 2006 18:14, Henry House wrote:
> > I have a set of surveyed-section boundaries* for northern California
> > from the United States Public Land Survey System and would like to use
> > GRASS to find geometric fractions of these roughly square sections.
> > For example, I would like to divide a particular section into equal
> > quarters by bisecting it east-west and north-south and then save the
> > northwest quarter for further analysis. Can anyone suggest a method to
> > do this acurately?
>
> .... it looks like we might be able to define the grid in terms of a
> lower-left point, and the width and height of grid cells, and an angle of
> rotation.
>

This would work reasonably well if all of your PLSS sections are
perfectly square. Having dealt with plss in northern california, I can
tell you that the sections in some rural and mountainous areas are not
always regular or even resembling a square. ( good quick example :
http://www.sco.wisc.edu/plss/plss_graphics/section_nosquare_200.jpg )

You might want to go to the county assessors office and see if you can
drum up the official data. Otherwise any attempt at trying to
"calculate" what are legally defined boundaries may get you in
trouble.

-- 
Matt Perry
perrygeo at gmail.com
http://www.perrygeo.net