[GRASS-user] v.lrs

GRASS GRASS user
1

Hello everybody,

I am trying to understand if GRASS fits me with its v.lrs module and how can I use it

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?
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

I loose myself in here already, didn’t really understood if grass can manage this method…?

so, stop the questions to this one for the moment but watch out cause more will come… :slight_smile:

Thank you and have a good day

2

On Tue, Jul 17, 2012 at 12:19 PM, Enrico G <mrenrich84@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

3

On 12/09/12 14:40, Markus Neteler wrote:

On Tue, Jul 17, 2012 at 12:19 PM, Enrico G<mrenrich84@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