|
|
| GeoCommunity Mailing List |
| |
| Mailing List Archives |
| Subject: | Re: GISList: SUM: Convert township-range-section to coordinates |
| Date: |
11/19/2001 11:55:11 PM |
| From: |
Michael Gallagher |
|
|
on 11/19/01 4:49 PM, Bryan Keith at bryan@geomega.com wrote:
> Well, this isn't much of a SUM since I still don't have an answer. Perhaps
> I wasn't completely clear in my initial post (included below). I had a
> number of suggestions and hints including how to calculate a polygon
> centroid, how convert long-lat to UTM, how to get the bounding coordinates
> of a polygon (none of which I was having trouble with). However, no one
> offered a technique to approximate the center of a quarter section if that
> section isn't roughly square. It's really a problem of not knowing what is
> meant by "northwest quarter of the northeast quarter of section 15" when
> section 15 looks more like a triangle than a square. Theoretically
> sections should be square, but there are many exceptions. I'm not fretting
> about it too much at this point since I still don't have the data that was
> supposed to make this an "urgent" problem two weeks ago. I'll post a real
> summary to this list if I find out anything new.
>
It may well be that the two systems are independent and cannot be converted.
Try talking to a surveyor, there must be surveyor listservs. There may be
information in the original plat that will give you geodetic control points,
but that still won't allow a conversion(except for the points themselves).
The PLSS was not consistent to the degree needed to convert to lat/long or
UTM. And it is unique to each state (I think) as well. It had a lot of
variation and later correction was a political process as much as a
technical one. In Wisconsin the iron deposits in the north resulted in large
magnetic errors and some vary odd township shapes.
You might be able to use the same points on a known base and your provided
files to to provide a Lat/Long reference. Projection distortion should not
be an issue given the typical scale township-range is used.
This would involve finding the same coverage in a different dataset that has
identifiable matching points in both (Road intersections, Town centers,
etc,) If you can scale and distort (hopefully just a little) the two files
until they match you could get your reference system. I do this sometimes in
my small scale mapping and can get files to match well within the precision
of the map, usually in about five minutes. Unprojected data should work ok.
Good luck
Mike Gallagher
Midwest Educational Graphics
To unsubscribe, write to gislist-unsubscribe@geocomm.com
________________________________________________________________________
Setup a GeoCommunity Account and have access to FAST DataDownloads
and Premium Career Posting at a discounted rate!
https://www.geocomm.com/cgi-bin/accounts/login
On-line Archives available at
http://spatialnews.geocomm.com/community/lists/
|
|
Sponsored by:
For information
regarding
advertising rates
Click Here!
|
