[GRASSLIST:9461] Re: strange behavior from v.to.points : feature or bug?

[Markus Neteler]

On Mon, Dec 05, 2005 at 09:24:55AM -0800, Dylan Beaudette wrote:
> Hi Radim,
> 
> Thanks for the pointers. Maybe a hint about this in the documentation 
> would be helpful, in case that I am not the only who gets mixed up with 
> this module.

done.

Markus
 
> Cheers,
> 
> Dylan
> 
> On Dec 5, 2005, at 4:28 AM, Radim Blazek wrote:
> 
> >Hi,
> >
> >I would say it is correct. At least what I intended.
> >dmax is realy maximum limit not exact ditance.
> >
> >If you need points on exact distance from the beginning
> >you should use v.segment.
> >
> >Radim
> >
> >On 12/4/05, Dylan Beaudette <dylan.beaudette at gmail.com> wrote:
> >>Noticed something strange in v.to.points in GRASS61-CVS (current)
> >>
> >>
> >>vector 't1' is 1000 meters long
> >>
> >>#this should extract 11 points, each 100 meters apart
> >>v.to.points -i in=t1 out=t1_points dmax=100
> >>
> >>resulting table:
> >>+------+------+------------------+
> >>| cat  | lcat | along            |
> >>+------+------+------------------+
> >>|    1 |    1 |                0 |
> >>|    2 |    1 | 90.9090909090943 |
> >>|    3 |    1 | 181.818181818189 |
> >>|    4 |    1 | 272.727272727283 |
> >>|    5 |    1 | 363.636363636377 |
> >>...
> >>|   11 |    1 | 909.090909090943 |
> >>|   12 |    1 | 1000.00000000004 |
> >>+------+------+------------------+
> >>
> >>notice that each point is about 90 meters apart, and there are 12
> >>points.
> >>
> >>now when i run v.to.points with dmax=110 :
> >>#this should extract 10 points, each 110 meters apart
> >>v.to.points -i in=t1 out=t1_points dmax=110
> >>
> >>resulting table:
> >>+------+------+------------------+
> >>| cat  | lcat | along            |
> >>+------+------+------------------+
> >>|    1 |    1 |                0 |
> >>|    2 |    1 | 100.000000000004 |
> >>|    3 |    1 | 200.000000000007 |
> >>....
> >>|   10 |    1 | 900.000000000034 |
> >>|   11 |    1 | 1000.00000000004 |
> >>+------+------+------------------+
> >>
> >>the correct and desired result!
> >>
> >>Any ideas on this {feature,bug} ?
> >>
> >>Thanks,
> >>
> >>--
> >>Dylan Beaudette
> >>Soils and Biogeochemistry Graduate Group
> >>University of California at Davis
> >>530.754.7341
> >>
> >>
> >
> >
> --
> Dylan Beaudette
> Soils and Biogeochemistry Graduate Group
> University of California at Davis
> 530.754.7341
> 

-- 
Markus Neteler     <neteler itc it>       http://mpa.itc.it
ITC-irst -  Centro per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
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