[mapserver-users] distance search in PLSS

[Puneet Kishor]

Rich,

Thanks for the insight... just as valuable as what Chip (Hankley) 
provided to me earlier, and what I learned in my "Intro to GIS" class 15 
years ago. What you guys say re PLSS is very true, and impt. to 
understand for anyone dealing with it.

My assumption that it is a "regular and continuous coverage" is _only_ 
for the sake of using the perl script... nothing more. I can't predict 
irregularities, and have no confusion with convergence, etc.

My problem was thus... given a piece of land that I happen to know has 
continuous coverage, I needed to identify all the qs within a given 
distance of a given qs. That is all. I need that to then further query a 
sql database to retrieve records that have been encoded with dtrsq. At 
this point I was not able to use a spatial approach to solving this, 
hence had to write the script. It was fun doing it (it is always fun 
writing arrays of hashes <g>).

You are not ranting at all... thanks for a valuable reminder about a 
useful system. Besides, anything that is described as being 
"boustrophedonic" can't be all that bad <g>.

pk/



On Monday, September 2, 2002, at 03:59  PM, Richard Greenwood wrote:

> 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 ½ 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 at GreenwoodMap.com
>> (307) 733-0203
>> http://www.GreenwoodMap.com