[GRASS-user] Survey descriptions to GRASS vector

[Dwight Needels]

On Aug 25, 2010, at 12:35 PM, Markus Neteler wrote:

> On Wed, Aug 25, 2010 at 4:27 PM, Dwight Needels <NEEDELS at translucida.com 
> > wrote:
>> Is there a straightforward way to encode a survey description of a  
>> parcel in
>> a text file that can then be imported into GRASS as a vector? The  
>> type of
>> description I am talking about looks something like this (where the  
>> numbers
>> are degrees/.minutes/seconds)...
>>
>> "Beginning at [a defined point], thence running North 40-35-00 East  
>> 1,125.90
>> feet to a point, thence turning and running South 01-01-13 West  
>> 288.89 feet
>> to a point, thence turning and running South 58-18-45 West 179.33  
>> feet to a
>> point, [...] , thence turning and running South 83-41-12 West 36.69  
>> feet to
>> the point of beginning."
>
> m.cogo comes to mind:
> http://grass.osgeo.org/grass64/manuals/html64_user/m.cogo.html
>
> for turning this into to true coordinates, then perhaps v.in.ascii.
>
> Markus

Fantastic!

I can bring the survey description in as a series of points by piping  
the output of m.cogo to v.in.ascii, as described in the manual.  
However, I had some difficulty running the shell script to import as a  
vector line map (I am running William Kyngesburye's 6.4RC6-3 on Mac OS  
X Leopard). It fails (as does the v.in.lines script) because 'tac' is  
not available on Mac OS.

I found a 2 year old defect report (Ticket #181) that discusses this  
problem in some detail. As described there, I replaced the tac command  
with 'tail -r', which worked. What is the status of a general fix for  
v.in.mapgen, v.in.lines and v.in.garmin? If it will be awhile, it  
would be nice to include the 'tail -r' tip for Mac OS users on the  
m.cogo manual page. Also, a m.cogo | v.in.lines piping example would  
be useful for non-Mac OS users.

One other thing that I have not been able to figure out is how to  
automatically close the line vector into a polygon to create an area  
for the parcel. Given the small number of vectors involved it is easy  
enough to manually edit each vector to close it, add a centroid, and  
convert lines to boundaries. However, is there a good way to  
accomplish the closing automatically? If so, is this something that  
could be added as an option in m.cogo (or perhaps a v.in.areas wrapper  
script that automatically takes care of all of the steps to close and  
generate areas)? Or perhaps even a general v.in.cogo script that  
imports a cogo.dat formatted file with options for bringing it in as  
points, a line, or an area.

Thanks, -Dwight