[GRASS-user] v.lrs

[Markus Neteler]

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.

On the other hand, GRASS supports deviations, see
http://grass.osgeo.org/grass64/manuals/html64_user/lrs.html

Sorry for the delay in answering,
Markus