[GRASS-user] v.lrs

Moritz Lennert mlennert at club.worldonline.be
Wed Sep 12 06:45:16 PDT 2012


On 12/09/12 14:40, Markus Neteler wrote:
> On Tue, Jul 17, 2012 at 12:19 PM, Enrico G<mrenrich84 at gmail.com>  wrote:
>> Hello everybody,
>>
>> I am trying to understand if GRASS fits me with its v.lrs module and how can
>> I use it
>
> I have created a (yet minimal) new Wiki page:
> http://grass.osgeo.org/wiki/Linear_Reference_System
>
> On the page, there are two articles listed which may be of interest,
>
>> I work as a marine surveyor mainly in the offshore oil&  gas industry,
>> occasionly cable&  environmental as well.
>> In this environment, everything is referenced to a (p)line and its offsets.
>>
>> Offset here are usually meters off a line, + or - outside a line (depending
>> on bearing), which is a different referencing method than the one used in
>> v.lrs, correct?
>
> In GRASS, an offset is the distance from a milepost along the line.
>
>> I.e.
>>
>> -------A------------------
>> 0----1----3----4----5----6
>> --------------------------
>> -------------------B------
>>
>> A = KP 1.25 DX =  1
>> B = KP 4.75 DX = -2
>>
>> where:
>> KP = miles post (distance from start of line)
>> DX = offset
>
> Why is this distance to the line important for you? It won't be
> reached anyway if not connected.

v.lrs.create has 'thresh' option to take into account points that are 
not exactly on the line.

You might want to use a combination of v.lrs.* + v.distance.

Moritz


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