[GRASSLIST:510] Re: [GRASS5] LRS

[Radim Blazek]

On 3/31/06, Markus Neteler <neteler at itc.it> wrote:
> Radim,
> (cc strk)
>
> this is great news! Maybe the wording could be synchronized
> with that of PostGIS?
>  http://postgis.refractions.net/docs/ch06.html#id2793484
>
> I think that Christoph Spoerri and strk are working on it:
>  http://postgis.refractions.net/pipermail/postgis-devel/2005-April/001338.html
>  http://postgis.refractions.net/pipermail/postgis-devel/2005-November/001652.html
>
> Since both GRASS-LRS and PostGIS-LRS are in development,
> it will hopefully be possible to synchronize the terminology.

The functions in PostGIS do not correspond exactly to v.lrs.* which
can better support real world data. The equivalent for line_interpolate_point()
and line_substring() in GRASS would be v.segment or Vect_line_segment()

v.lrs.* does more, it can generate LRS from layer of lines and points
eg roads and milestones.

I am using the mentioned PostGIS functions for example  in WebGIS application
(PHP/PostGIS/AJAX) which is using the data (linear layer + lrs table)
generated by v.lrs.create. The lrs table is mapping real world to GIS.
The mapping is necessary because lines in GIS do not exacly correspond
to physical objects.

The LRS in GRASS is on higher application level then the functions in PostGIS.
Note that I dont say it is superior, it just do something else - more.
That is the reason we cannot probably find equivalents in terminology.

Radim


> Markus
>
> On Fri, Mar 31, 2006 at 11:13:24AM +0200, Radim Blazek wrote:
> > I would like to include my implementation of LRS
> > (lineare reference system) which was available here
> > http://mpa.itc.it/radim/lrs/index.html
> > in standard GRASS distribution.
> >
> > The LRS supports georeferencing of points and segments
> > given by linear feature, e.g. a road and a position on the
> > linear feature in real world for exemple km+meters.
> > It can also do reverse task, that means to report linear feature
> > and position (road nr., km+m) for point (near the road).
> >
> > I have a question about terminology, I am in doubts how to call
> >
> > 1) The value specifying certain fix point in real world, e.g.
> >   milepost, milestone. The point has usually a physical representation
> >   but I mean the value it represents i.e. mile, kilometer,
> >   not the physical object.
> >
> > 2) The value which specifies the distance along a linear object
> >     from 1) (from milepost) to a certain position on the linear feature.
> >     The distance is given for example in meters or feets.
> >
> > 3) How to call the module which generates labels of existing LRS
> >     Here is example of a map with labels and strokes generated
> >     byt this module: http://mpa.itc.it/radim/lrs/stationing-small.png
> >
> > I hope that native english speakers and people working with LRS can help.
> >
> > Thanks
> > Radim
>