[GRASS-user] perpendicular segments to a line

GRASS GRASS user
1

Dear all,
does someone know if there's a simple way to create perpendicolar
segments to a lines (equispaced along this line)???
like this...

| | | | |
-------------------
| | | | |

I have had a look to v.lrs.XXX but I have got some problems to
understand the needed parameters.. also looking at the papers from Radim
didn't help me...
what I need is probably a simple tutorial or something similar...
I mean.. if someone can help me with this topic I can write a wiki page
on this...
but at the moment I can't understand wich can be the simpler way to
solve this problem...
v.segment?
v.split?
v.to.points?
v.lrs.XXX?

I'am quite confused!!!

thank you

Ivan

--
Ivan Marchesini
Department of Civil and Environmental Engineering
University of Perugia
Via G. Duranti 93/a
06125
Perugia (Italy)
e-mail: marchesini@unipg.it
        ivan.marchesini@gmail.com
tel: +39(0)755853760
fax: +39(0)755853756
jabber: geoivan73@jabber.org

2

ivan marchesini wrote:

Dear all,
does someone know if there's a simple way to create perpendicolar
segments to a lines (equispaced along this line)???
like this...

| | | | |
-------------------
| | | | |

How about this:

0. Make sure you input line has categories.

1. Create close parallel lines on the sides of your input line (choose
the distance that suits you):
v.parallel input=center_line output=left distance=0.00001
v.parallel input=center_line output=right distance=-0.00001

2. Calculate the offsets as needed, then use them to create points on
desired locations, along the lines on the 2 sides of your input line:
cat offsets | v.segment input=right output=right_seg
cat offsets | v.segment input=left output=left_seg

3. Connect the closest points:
v.distance from=left_seg to=right_seg from_type=point to_type=point
output=shorties dmax=-1

4. Patch "shorties" with your input (v.patch)

5. Break at crossings (v.clean type=line tool=break)

You obtain a topologically clean line with crossbars.

Maciek

3

ivan marchesini wrote:

Dear all,
does someone know if there's a simple way to create perpendicolar
segments to a lines (equispaced along this line)???
like this...

| | | | |
-------------------
| | | | |

I have had a look to v.lrs.XXX but I have got some problems to
understand the needed parameters.. also looking at the papers from
Radim didn't help me...
what I need is probably a simple tutorial or something similar...
I mean.. if someone can help me with this topic I can write a wiki
page on this...
but at the moment I can't understand wich can be the simpler way to
solve this problem...
v.segment?
v.split?
v.to.points?
v.lrs.XXX?

m.cogo might help as part of a script,

Description:
A simple utility for converting bearing and distance measurements to
coordinates and vice versa. It assumes a cartesian coordinate system

Hamish