[GRASS-user] linear referencing system - has anyone used it?

GRASS GRASS user
1

I posted a question a few weeks ago about the linear referencing system. Has anyone actually used it to make new maps from field data? Unfortunately the developer of this function (Radim Blazek) no longer works on Grass. Below is a copy of my original question.

Thanks and cheers.

Fellow GRASS users,

I would like to build a new point data layer from a large database of stream
surveys which have 2 pieces of spatial info:

1) an LLID number for that stream
2) distance from the start of that stream

Based on what I have seen, I would use the linear referencing system
modules. I am not sure if I need to build a new reference layer as I have a
stream layer with the LLID info already in it. Additionally, I could not
find an example of how v.lrs.segment works in practice. I have attempted to
summarize things as I understand it to help make it easier to answer my
questions. As I understand it the input parameters for v.lrs.segment would
be as follows:

1) input= the stream layer with the associated LLID info
2) output = the name of the output layer
3) llayer = whether it is a point or line (is it 1 for line and 0 for
point?)
4) rsdriver = I don't know what this means
5) rsdatabase = the location of the file with the LLID # and distance
6) rstable = the name of the file which has the LLID number and distance?
will it automatically add in the other data in the database? Or do I do
that later using a spreadsheet program on the .dbf

As I am still learning how to do this, I expect I will have more questions
in the future. Hopefully this will be of use to others as well. Many
thanks in advance. Cheers.

Lindsay Mico
Environmental Consultant
Demeter Design LLC
(503) 368-7195
http://demeterdesign.net
"Thoughtful Planning is the Surest Investment"

2

On Wed, 14 Mar 2007 12:37:28 -0800
Lindsay Mico wrote:

I posted a question a few weeks ago about the linear referencing system.
Has anyone actually used it to make new maps from field data? Unfortunately
the developer of this function (Radim Blazek) no longer works on Grass.
Below is a copy of my original question.

Thanks and cheers.

Fellow GRASS users,

I would like to build a new point data layer from a large database of stream
surveys which have 2 pieces of spatial info:

1) an LLID number for that stream
2) distance from the start of that stream

I've only used v.lrs.segment with single line segments, not networks
of lines. For this I passed this type of information formated as:

P stoptext catnum offset

in a text file and piped it to the command.

Based on what I have seen, I would use the linear referencing system
modules. I am not sure if I need to build a new reference layer as I have a
stream layer with the LLID info already in it. Additionally, I could not
find an example of how v.lrs.segment works in practice. I have attempted to
summarize things as I understand it to help make it easier to answer my
questions. As I understand it the input parameters for v.lrs.segment would
be as follows:

1) input= the stream layer with the associated LLID info
2) output = the name of the output layer
3) llayer = whether it is a point or line (is it 1 for line and 0 for
point?)

Please refer to the GRASS vector intro for details on layers within
vector files. Essentially, unless you are messing with this "feature"
it will always be 1.

4) rsdriver = I don't know what this means

dbf, pgsql, sqlite, etc

5) rsdatabase = the location of the file with the LLID # and distance

name of database, for example name of sql database.

6) rstable = the name of the file which has the LLID number and distance?

table name

will it automatically add in the other data in the database? Or do I do
that later using a spreadsheet program on the .dbf

As I am still learning how to do this, I expect I will have more questions
in the future. Hopefully this will be of use to others as well. Many
thanks in advance. Cheers.

It is useful to read through all the material in the tutorial if you
haven't already done so.

T
--
Trevor Wiens
twiens@interbaun.com

The significant problems that we face cannot be solved at the same
level of thinking we were at when we created them.
(Albert Einstein)