[postgis-users] working with PLSS: state-plane survey system coordinates

[Dylan Beaudette]

Hi everyone,

Here is a rather odd question: 

say i have a vector description of 'sections' as defined in the PLSS 
(http://nationalatlas.gov/articles/boundaries/a_plss.html), and I would like 
associate legal definitions with a real-world coordinates.

starting with "T10, R10, Section 10, mount diablo base meridian" , it would be 
a simple matter to lookup the matching section polygon, locate its centroid, 
and dump the x,y coordinates. 

however, it is common practice to define a location in terms of 1/4 of 1/4 
section, i.e. :

"NE 1/4 of NE 1/4 of Section 10, T10, R10"

the problem then arises: how can i approximately subdivide the section polygon 
(as it is usually not a square) such that : the polygon is bisected along 
each axis twice:

+------+------+
|         |    | * |
|         +--+--|
|         |    |   |
+------+------+
|         |        |
|         |        |
|         |        |
+------+------+

note that the NE 1/4 of the NE 1/4 of the section is marked with a * . also 
note that the section will not always be oriented parallel to the x and y 
axis as in the example above. 

therefore the question is : is there a generic way to bisect a polygon 
resembling a square (an approximation is ok too) within an x,y plane ?

ideas?

thanks!


-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341