Dear list,
Following the GRASSNews_vol3 article on SRTM import, I was trying to sharpen coastlines using GSHHS shapefiles. However, the imported GSHHS vectors are just lines and not areas. Therefore I do not know how to generate a raster MASK, because there is no area for v.to.rast to produce a filled raster coverage.
Thanks in advance for any help,
Luigi
--
GRASS6/cygwin user
I don't know what to do about the GSHHS coastlines off the top of my head, but if you use the version 2 SRTM, that's all taken care of. It's had all ocean areas identified and flat-filled with 0 elevation, and many lakes have also been identified and flat-filled with the lake elevation. No more noise in the water areas. There are also polygon shapefiles of the mask used to do this.
On Mar 25, 2006, at 1:09 AM, Luigi Ponti wrote:
Dear list,
Following the GRASSNews_vol3 article on SRTM import, I was trying to sharpen coastlines using GSHHS shapefiles. However, the imported GSHHS vectors are just lines and not areas. Therefore I do not know how to generate a raster MASK, because there is no area for v.to.rast to produce a filled raster coverage.
Thanks in advance for any help,
Luigi
--
GRASS6/cygwin user
-----
William Kyngesburye <kyngchaos@kyngchaos.com>
http://www.kyngchaos.com/
"History is an illusion caused by the passage of time, and time is an illusion caused by the passage of history."
- Hitchhiker's Guide to the Galaxy
This site also offers SRTM processed data:
http://srtm.csi.cgiar.org/index.asp
Carlos
On 3/25/06, William Kyngesburye <woklist@kyngchaos.com> wrote:
I don't know what to do about the GSHHS coastlines off the top of my
head, but if you use the version 2 SRTM, that's all taken care of.
It's had all ocean areas identified and flat-filled with 0 elevation,
and many lakes have also been identified and flat-filled with the
lake elevation. No more noise in the water areas. There are also
polygon shapefiles of the mask used to do this.On Mar 25, 2006, at 1:09 AM, Luigi Ponti wrote:
> Dear list,
>
> Following the GRASSNews_vol3 article on SRTM import, I was trying
> to sharpen coastlines using GSHHS shapefiles. However, the imported
> GSHHS vectors are just lines and not areas. Therefore I do not know
> how to generate a raster MASK, because there is no area for
> v.to.rast to produce a filled raster coverage.
>
> Thanks in advance for any help,
>
> Luigi
>
> --
> GRASS6/cygwin user
>-----
William Kyngesburye <kyngchaos@kyngchaos.com>
http://www.kyngchaos.com/"History is an illusion caused by the passage of time, and time is an
illusion caused by the passage of history."- Hitchhiker's Guide to the Galaxy
--
+-----------------------------------------------------------+
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
Carlos "Guâno" Grohmann wrote:
This site also offers SRTM processed data:
http://srtm.csi.cgiar.org/index.asp
Carlos
and .....
William Kyngesburye <kyngchaos@kyngchaos.com>
"History is an illusion caused by the passage of time, and time is an
illusion caused by the passage of history."- Hitchhiker's Guide to the Galaxy
This email is only a sad note of the situation. First of all, that slogan fits well now.
I look at the site. Unfortunately the data is not global. Northern limit goes some hundred meters north from by home. So there is missing even some countries.
Sigh.
I just read the newsletter article and started to use my Saturday evening nicely. ;-(
Best regards from a country which doesn't exist,
Kari
--
Kari Salovaara
Hanko, Finland
Following the GRASSNews_vol3 article on SRTM import, I was trying to
sharpen coastlines using GSHHS shapefiles. However, the imported GSHHS
vectors are just lines and not areas. Therefore I do not know how to
generate a raster MASK, because there is no area for v.to.rast to
produce a filled raster coverage.
others have mentioned the new SRTM v2 so I'll leave that, but for the
general vector how-to question:
An area is made up of a boundary and a centroid, so two steps are
needed:
# convert lines to boundaries
v.type line,boundary
# add centroids
v.category op=add # ?!!!
This second part I know possible, but I forget the correct command.
Maybe it is v.build or v.clean?
Hamish
Hamish wrote:
Following the GRASSNews_vol3 article on SRTM import, I was trying to
sharpen coastlines using GSHHS shapefiles. However, the imported GSHHS
vectors are just lines and not areas. Therefore I do not know how to
generate a raster MASK, because there is no area for v.to.rast to
produce a filled raster coverage.
others have mentioned the new SRTM v2 so I'll leave that, but for the
SRTM V2 is really recommended. They also ship their water masks along
with the
updated SRTM data.
general vector how-to question:
An area is made up of a boundary and a centroid, so two steps are
needed:# convert lines to boundaries
v.type line,boundary# add centroids
v.category op=add # ?!!!This second part I know possible, but I forget the correct command.
g.manual v.category
4) Add categories/centroids to a vector map without categories
v.category in=wkt out=wktnew option=add
Markus
William, Eric, Carlos, Hamish, Markus:
Thanks erverybody for your suggestions,
I used GeoTIFF WRS-2 tiles from GLCF, so I have probably wasted a fair amount of time filling voids etc. However, as Hamish would say, not really a waste of time cause I learned something on r.fillnulls and r.resamp.rst.
Hamish: thank you for the hint on the vector general question. I have been playing aroung with v.type for quite a while, then I decided to ask for help. Good, for two reasons. First, I got to know about srtm2. Second, now I know it is possible to build area topology from lines.
Thank you all again and if anybody knows the correct command to add centroids to boundaries, please let me know.
Luigi
P.S. While I was writing this message, Markus filled the gap: THANKS!!!
On Sun, 26 Mar 2006 16:36:32 +1200
Hamish <hamish_nospam@yahoo.com> wrote:
Following the GRASSNews_vol3 article on SRTM import, I was trying to sharpen coastlines using GSHHS shapefiles. However, the imported GSHHS
vectors are just lines and not areas. Therefore I do not know how to generate a raster MASK, because there is no area for v.to.rast to produce a filled raster coverage.others have mentioned the new SRTM v2 so I'll leave that, but for the
general vector how-to question:An area is made up of a boundary and a centroid, so two steps are
needed:# convert lines to boundaries
v.type line,boundary# add centroids v.category op=add # ?!!!
This second part I know possible, but I forget the correct command.
Maybe it is v.build or v.clean?Hamish
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