I'm trying to extract only the largest rivers from a very detailed
hydrology map (mostly for display purposes). Right now the map just
looks black with lines. I've managed to use v.extract for areas but
since the rivers are in segments i can't use v.extract for lengths.
I've tried v.clean snap but it doesn't seem to be doing what I want it
to. Any advice?
-Colin
Colin Nielsen napisał(a):
I'm trying to extract only the largest rivers from a very detailed
hydrology map (mostly for display purposes). Right now the map just
looks black with lines. I've managed to use v.extract for areas but
since the rivers are in segments i can't use v.extract for lengths.
I've tried v.clean snap but it doesn't seem to be doing what I want it
to. Any advice?-Colin
_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser
for now (with my previous experiences with exactly the same problem) v.digit seems to be the fastest solution 
With over to 10,000 river segments that isn't exactly a practical
solution for me. Anything else?
On 3/22/07, Jarek Jasiewicz <jarekj@amu.edu.pl> wrote:
Colin Nielsen napisa³(a):
> I'm trying to extract only the largest rivers from a very detailed
> hydrology map (mostly for display purposes). Right now the map just
> looks black with lines. I've managed to use v.extract for areas but
> since the rivers are in segments i can't use v.extract for lengths.
> I've tried v.clean snap but it doesn't seem to be doing what I want it
> to. Any advice?
>
> -Colin
>
> _______________________________________________
> grassuser mailing list
> grassuser@grass.itc.it
> http://grass.itc.it/mailman/listinfo/grassuser
for now (with my previous experiences with exactly the same problem)
v.digit seems to be the fastest solution
Perhaps v.to.db to add the length of each segment to the database, and
then v.extract? or SQL thru gis.m to create a new map?
Carlos
On 3/22/07, Colin Nielsen <colin.nielsen@mail.mcgill.ca> wrote:
With over to 10,000 river segments that isn't exactly a practical
solution for me. Anything else?On 3/22/07, Jarek Jasiewicz <jarekj@amu.edu.pl> wrote:
> Colin Nielsen napisa³(a):
> > I'm trying to extract only the largest rivers from a very detailed
> > hydrology map (mostly for display purposes). Right now the map just
> > looks black with lines. I've managed to use v.extract for areas but
> > since the rivers are in segments i can't use v.extract for lengths.
> > I've tried v.clean snap but it doesn't seem to be doing what I want it
> > to. Any advice?
> >
> > -Colin
> >
> > _______________________________________________
> > grassuser mailing list
> > grassuser@grass.itc.it
> > http://grass.itc.it/mailman/listinfo/grassuser
> for now (with my previous experiences with exactly the same problem)
> v.digit seems to be the fastest solution
>_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser
--
+-----------------------------------------------------------+
Carlos Henrique Grohmann - Guano
Geologist M.Sc - Doctorate Student at IGc-USP - Brazil
Linux User #89721 - carlos dot grohmann at gmail dot com
+-----------------------------------------------------------+
_________________
"Good morning, doctors. I have taken the liberty of removing Windows
95 from my hard drive."
--The winning entry in a "What were HAL's first words" contest judged
by 2001: A SPACE ODYSSEY creator Arthur C. Clarke
� napisał(a):
Perhaps v.to.db to add the length of each segment to the database, and
then v.extract? or SQL thru gis.m to create a new map?Carlos
it is not a good solution there are no rules on segment lenght in river network (there can be short segement in main stream and longer in tributaries and opposite)
On 3/22/07, Colin Nielsen <colin.nielsen@mail.mcgill.ca> wrote:
With over to 10,000 river segments that isn't exactly a practical
solution for me. Anything else?On 3/22/07, Jarek Jasiewicz <jarekj@amu.edu.pl> wrote:
> Colin Nielsen napisa�(a):
> > I'm trying to extract only the largest rivers from a very detailed
> > hydrology map (mostly for display purposes). Right now the map just
> > looks black with lines. I've managed to use v.extract for areas but
> > since the rivers are in segments i can't use v.extract for lengths.
> > I've tried v.clean snap but it doesn't seem to be doing what I want it
> > to. Any advice?
> >
> > -Colin
> >
> > _______________________________________________
> > grassuser mailing list
> > grassuser@grass.itc.it
> > http://grass.itc.it/mailman/listinfo/grassuser
> for now (with my previous experiences with exactly the same problem)
> v.digit seems to be the fastest solution
>_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser
well problem is on
What if you convert the vector to raster, then back to vector? each
stream should be one segment.
On 3/22/07, Jarek Jasiewicz <jarekj@amu.edu.pl> wrote:
� napisał(a):
> Perhaps v.to.db to add the length of each segment to the database, and
> then v.extract? or SQL thru gis.m to create a new map?
>
> Carlos
it is not a good solution there are no rules on segment lenght in river
network (there can be short segement in main stream and longer in
tributaries and opposite)
>
> On 3/22/07, Colin Nielsen <colin.nielsen@mail.mcgill.ca> wrote:
>> With over to 10,000 river segments that isn't exactly a practical
>> solution for me. Anything else?
>>
>> On 3/22/07, Jarek Jasiewicz <jarekj@amu.edu.pl> wrote:
>> > Colin Nielsen napisa�(a):
>> > > I'm trying to extract only the largest rivers from a very detailed
>> > > hydrology map (mostly for display purposes). Right now the map just
>> > > looks black with lines. I've managed to use v.extract for areas but
>> > > since the rivers are in segments i can't use v.extract for lengths.
>> > > I've tried v.clean snap but it doesn't seem to be doing what I
>> want it
>> > > to. Any advice?
>> > >
>> > > -Colin
>> > >
>> > > _______________________________________________
>> > > grassuser mailing list
>> > > grassuser@grass.itc.it
>> > > http://grass.itc.it/mailman/listinfo/grassuser
>> > for now (with my previous experiences with exactly the same problem)
>> > v.digit seems to be the fastest solution
>> >
>>
>> _______________________________________________
>> grassuser mailing list
>> grassuser@grass.itc.it
>> http://grass.itc.it/mailman/listinfo/grassuser
>>
>
well problem is on
--
+-----------------------------------------------------------+
Carlos Henrique Grohmann - Guano
Geologist M.Sc - Doctorate Student at IGc-USP - Brazil
Linux User #89721 - carlos dot grohmann at gmail dot com
+-----------------------------------------------------------+
_________________
"Good morning, doctors. I have taken the liberty of removing Windows
95 from my hard drive."
--The winning entry in a "What were HAL's first words" contest judged
by 2001: A SPACE ODYSSEY creator Arthur C. Clarke
Colin Nielsen napisał(a):
With over to 10,000 river segments that isn't exactly a practical
solution for me. Anything else?On 3/22/07, Jarek Jasiewicz <jarekj@amu.edu.pl> wrote:
Colin Nielsen napisa�(a):
> I'm trying to extract only the largest rivers from a very detailed
> hydrology map (mostly for display purposes). Right now the map just
> looks black with lines. I've managed to use v.extract for areas but
> since the rivers are in segments i can't use v.extract for lengths.
> I've tried v.clean snap but it doesn't seem to be doing what I want it
> to. Any advice?
>
> -Colin
>
> _______________________________________________
> grassuser mailing list
> grassuser@grass.itc.it
> http://grass.itc.it/mailman/listinfo/grassuser
for now (with my previous experiences with exactly the same problem)
v.digit seems to be the fastest solution
have you some addational atributies on segment?
It is digitised map (it produced a segment between every juncion) without categories and another atributies?
If so, there is no solution in grass (IMHO), but you can search solution in JGRASS in tool called horton machine it seems it will help you, also look for solution in TAS (Terrain analisys system WINDOWS only, free strahler analisys) or maybe the best fot this TauDEM free extension for ArcGIS (not free) and Mapwindow (free), but I don't guarantee success.
or it is regulral hydrological map with adational attributies if so there shall be some addational atributies like hydrological id or name, SQL shall help
cherrs
Jarek
� napisał(a):
What if you convert the vector to raster, then back to vector? each
stream should be one segment.
no, there be much more addational segments. Wrong way. (about twice, as I tried few seconds before)
On 3/22/07, Jarek Jasiewicz <jarekj@amu.edu.pl> wrote:
� napisał(a):
> Perhaps v.to.db to add the length of each segment to the database, and
> then v.extract? or SQL thru gis.m to create a new map?
>
> Carlos
it is not a good solution there are no rules on segment lenght in river
network (there can be short segement in main stream and longer in
tributaries and opposite)
>
> On 3/22/07, Colin Nielsen <colin.nielsen@mail.mcgill.ca> wrote:
>> With over to 10,000 river segments that isn't exactly a practical
>> solution for me. Anything else?
>>
>> On 3/22/07, Jarek Jasiewicz <jarekj@amu.edu.pl> wrote:
>> > Colin Nielsen napisa�(a):
>> > > I'm trying to extract only the largest rivers from a very detailed
>> > > hydrology map (mostly for display purposes). Right now the map just
>> > > looks black with lines. I've managed to use v.extract for areas but
>> > > since the rivers are in segments i can't use v.extract for lengths.
>> > > I've tried v.clean snap but it doesn't seem to be doing what I
>> want it
>> > > to. Any advice?
>> > >
>> > > -Colin
>> > >
>> > > _______________________________________________
>> > > grassuser mailing list
>> > > grassuser@grass.itc.it
>> > > http://grass.itc.it/mailman/listinfo/grassuser
>> > for now (with my previous experiences with exactly the same problem)
>> > v.digit seems to be the fastest solution
>> >
>>
>> _______________________________________________
>> grassuser mailing list
>> grassuser@grass.itc.it
>> http://grass.itc.it/mailman/listinfo/grassuser
>>
>
well problem is on
Colin Nielsen wrote:
I'm trying to extract only the largest rivers from a very detailed
hydrology map (mostly for display purposes). Right now the map just
looks black with lines. I've managed to use v.extract for areas but
since the rivers are in segments i can't use v.extract for lengths.
I've tried v.clean snap but it doesn't seem to be doing what I want it
to. Any advice?
v.build.polylines
There are bugs in 6.2 in this module (easy to workaround, and fixed for
good in 6.3 by Martin Landa):
https://intevation.de/rt/webrt?serial_num=4249
Workaround: run 'v.clean tool=prune thresh=0' on the v.bulid polylines
output. It will remove the bogus doubled vertices.
https://intevation.de/rt/webrt?serial_num=4247
Applies only to boundaries anyway.
After you transform segmented lines into polylines you should be able
to use v.extract by length.
Maciek