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Re: [mapserver-users] distance search in PLSS

Puneet, et al,

I followed this thread and I know that Puneet’s assumption is a “regular and continuous coverage of PLSS”, but as a land surveyor, I have to throw on here. I do not mean to question Puneet’s application of his algorithm, but just for the record, I wanted to clarify what the PLSS is and is not.

The PLSS is not, and was never intended to be “regular” grid anything like a map projection system. The PLSS is not a mapping system that can be treated like a UTM or State Plane zone. It is a means for describing and conveying real property.

Where a mapping system maintains rectangularity throughout a zone, the PLSS only attempted to maintain rectangularity within a single township, and even there it is not particularly rectangular. The east line of a township was to be geodetic north, with the rest of the lines parallel. The west line, being the east line of the next township, was also geodetic north, so obviously not parallel with the other lines in the township due to convergence. Similarly, the east-west lines were adjusted for convergence every four townships (depending on region) causing large east-west shifts every 24 miles as you go north or south. (Nearly ˝ mile at my latitude, 43N)

In addition to the lack of rectangularity beyond the township, there are an endless array of other things that preclude a “regular” coverage, such as water bodies and senior rights or surveys. Senior rights or surveys include things like Homestead Entry Surveys, Indian and Military Reservations, and state lines. Independent resurvey, which are quite common in some areas of the western states due to fraudulent original surveys, completely muck up the works.

Sorry if I sound like I’m ranting. I don’t mean to be critical of anyone. The PLSS is a truly remarkable system that has served us well for nearly 225 years. I have a great respect for the PLSS, and I am just trying to share a bit of that.

Rich

At 01:04 AM 9/2/2002 -0500, you wrote:
I have posted a perl script called plsscalc.pl at the above wiki. Given a township, range, section, quarter-section, and a search radius in miles, this script will spit out all the quarter-sections within the search radius of the origin. Assumes regular and continuous coverage of PLSS.

Hope this helps someone.

pk/



On Thursday, August 29, 2002, at 09:52 AM, Puneet Kishor wrote:

Thanks for the advice Ed. I thought of generating a table, but I really want to do this with a script so I can specify the distance. Anyway... all this discussion has got me thinking and I am putting together a Perl script that might be able to do what I want. When I get it working right I will post it here for others.

Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich@GreenwoodMap.com
(307) 733-0203
http://www.GreenwoodMap.com