[GRASS-user] Georeferencing vectors and r.thin

GRASS GRASS user
,
1

Hello,
I’m trying to georeference a chart in PDF into a lat-long location. I first convert it into JPG, import it into the unreferenced location using r.in.gdal and so on (as seen on the tutorial). I need to digitize most lines of the original chart and it looks tedious. I’ve tried using r.thin (to convert it to vector with r.lines), but I get the following:

GRASS 6.0.2 (lemd):~/a > r.thin input=a_rect output=a_lines
File a_rect – 3333333 rows X 3333333 columns
(null): open_file: error writing temporary file

Does anyone know how to solve this? Anyway, is it possible to directly georeference the original chart in some vectorial format converted from the PDF without having to make the conversion to an image?
Thanks very much in advance, and excuse this newbie questions. Regards,

Juan Daniel López

2

On Fri, 23 Jun 2006 18:07:51 +0200
"Juan Daniel López Serna" <jjuanda@gmail.com> wrote:

Hello,
    I'm trying to georeference a chart in PDF into a lat-long
location. I first convert it into JPG,

Wouldn't be some non-lossy format better, eg. PNG?

import it into the unreferenced location using r.in.gdal and so on
(as seen on the tutorial). I need to digitize most lines of the
original chart and it looks tedious. I've tried using r.thin (to
convert it to vector with r.lines)

You mean r.to.vect feature=line, right?

, but I get the following:

GRASS 6.0.2 (lemd):~/a > r.thin input=a_rect output=a_lines
File a_rect -- 3333333 rows X 3333333 columns
(null): open_file: error writing temporary file

There have been several fixes to r.thin this year in Grass 6.1. Can you
try a 6.1 CVS snapshot (I don't think that these days it is any less
stable than 6.02, yet much more featurefull and has many bugs fixed,
which are still present in 6.02).

Maciek

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3

On Fri, Jun 23, 2006 at 06:53:57PM +0200, Maciek Sieczka wrote:

On Fri, 23 Jun 2006 18:07:51 +0200
"Juan Daniel López Serna" <jjuanda@gmail.com> wrote:

...

>, but I get the following:
>
> GRASS 6.0.2 (lemd):~/a > r.thin input=a_rect output=a_lines
> File a_rect -- 3333333 rows X 3333333 columns
> (null): open_file: error writing temporary file

3333333 * 3333333

[1] 1.111111e+13

this looks like a pretty big number to me... are you sure that
you want this size?

Markus

4

Hi,
Thanks very much for your answers. Obviously I didnt realized that I was trying to use such a big number, that confirms that I’m a novice in GRASS.
Anyway, apart from correcting the way I proceed with such a big image, I state again the second question in my mail: Is it possible to directly georeference the image in some vector format without having to convert it to raster first?
Thanks again. Regards,

Juan Daniel López

On 6/23/06, Markus Neteler <neteler@itc.it> wrote:

On Fri, Jun 23, 2006 at 06:53:57PM +0200, Maciek Sieczka wrote:

On Fri, 23 Jun 2006 18:07:51 +0200
“Juan Daniel López Serna” <jjuanda@gmail.com> wrote:
…

, but I get the following:

GRASS 6.0.2 (lemd):~/a > r.thin input=a_rect output=a_lines
File a_rect – 3333333 rows X 3333333 columns
(null): open_file: error writing temporary file

3333333 * 3333333
[1] 1.111111e+13

this looks like a pretty big number to me… are you sure that
you want this size?

Markus

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5

On Fri, 23 Jun 2006 22:13:21 +0200
"Juan Daniel López Serna" <jjuanda@gmail.com> wrote:

Hi,
   Thanks very much for your answers. Obviously I didnt realized that
I was trying to use such a big number, that confirms that I'm a
novice in GRASS. Anyway, apart from correcting the way I proceed with
such a big image, I state again the second question in my mail: Is it
possible to directly georeference the image in some vector format
without having to convert it to raster first?

Yes. Once you load the vector into Grass (using any v.in.*, v.external
maybe enough too?) use v.transform.

Maciek

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6

Juan Daniel López Serna wrote:

Is it possible to directly georeference the image in some vector
format without having to convert it to raster first?

use v.transform

Hamish