I am trying to import an contour file and trying to come up with an DEM map
from it. I tried it my way but end up with wrong output. I am looking
forward for some one who can import this map and convert it to DEM and
finally and most importantly we should be able to view the output in NVIZ. I
have attached the folder having the contour data, this data is of IIT
bombay.
If someone succeeds in doing this, please send me the procedure (with all
the details of resolution, grid size etc). I will be very thankful to one
who helps me out of this problem.
regards,
Nikhil Morajkar
Junior Software Engineer,
Department of computer science and Engineering,
Geo-Spatial Information Science & Engineering (GISE),
Advance Research Lab,
Indian Institute of Technology, Bombay (IITB)
Powai, Mumbai
I am trying to import an contour file and trying to come up with an DEM map
from it. I tried it my way but end up with wrong output. I am looking
forward for some one who can import this map and convert it to DEM and
finally and most importantly we should be able to view the output in NVIZ. I
have attached the folder having the contour data, this data is of IIT
bombay.
If someone succeeds in doing this, please send me the procedure (with all
the details of resolution, grid size etc). I will be very thankful to one
who helps me out of this problem.
Thanks for replying.I tried many things like v.surf.rst, r.surf.contour etc
but still I could'nt get the desired output, sometimes it runs for a
long-long time which never ends and sometimes after the resolution being
changed it gives weird output and which cannot be viewed in NVIZ it says
loading failed. I had posted the problems that I faced but did not get
reply/help, so this time around I have uploaded the datafile so that one can
just try out the thing on their machine and see if its possible and works
fine on their system and kindly help me in my work. I have spent more than 2
weeks on this and have not succeeded yet. I think the problem is with
resolution. I need serious help from someone.
It is in lat-long, isnt it? Or a different projection?
I figured out, that the hight column is not numeric, but character.
Maybe thats he problem?
using:
v.surf.rst input=kontour@mapset elev=kontour_dem
after converting hight to integer and
setting resolution to
0:00:01
I get: see attached
Achim
Am 09.11.2010 13:12, schrieb nikmor:
hey Achim
Thanks for replying.I tried many things like v.surf.rst, r.surf.contour etc
but still I could'nt get the desired output, sometimes it runs for a
long-long time which never ends and sometimes after the resolution being
changed it gives weird output and which cannot be viewed in NVIZ it says
loading failed. I had posted the problems that I faced but did not get
reply/help, so this time around I have uploaded the datafile so that one can
just try out the thing on their machine and see if its possible and works
fine on their system and kindly help me in my work. I have spent more than 2
weeks on this and have not succeeded yet. I think the problem is with
resolution. I need serious help from someone.
I think the output you got is correct. But when i try to change the
resolution (eg: 0:00:01) in the g.region resolution tab(GRID resolution 2D
both north-south and east-west), it gives an error saying :ERROR: Invalid
input <res=0:00:01>". Am i doing something wrong???. And one more thing is
that how have you converted the height to integer please give me details of
this too. I am really very thankful for your time and effort.
> And one more thing is
> that how have you converted the height to integer please give me details of
> this too. I am really very thankful for your time and effort.
There are many ways. For example like Micha said:
--%<--
I'm including a mapset "bombay" with the contour vecto, the contour raster and the resulting dem.
Like Achim said, first you must convert the HEIGHT column to integer (I did this with Openoffice Calc).
--%<--
here he means the dbf-file
or you change the table after imported
(using SQL)
I think the output you got is correct. But when i try to change the
resolution (eg: 0:00:01) in the g.region resolution tab(GRID resolution 2D
both north-south and east-west), it gives an error saying :ERROR: Invalid
input<res=0:00:01>". Am i doing something wrong???.
check your projection units (g.proj -p)
and your region (g.region -p)
On Tue, Nov 9, 2010 at 12:28 PM, nikmor <nikhil_morajkar@yahoo.com> wrote:
Hello friends
I am trying to import an contour file and trying to come up with an DEM map
from it. I tried it my way but end up with wrong output. I am looking
forward for some one who can import this map and convert it to DEM and
finally and most importantly we should be able to view the output in NVIZ. I
have attached the folder having the contour data, this data is of IIT
bombay.
thanks for the link. I have tried it out and it works with v.surf.rst. But when I use r.surf.contour it takes a very very long time and it never ends. I would be thankful if you could suggest me something regarding the resolution(grid resolution 2d in g.region modules resolution tab).
thanks,
Nikhil Morajkar Junior Software Engineer, Department of Computer Science and Engineering, Geo-Spatial Information Science & Engineering (GISE), Advance Research Lab, Indian Institute of Technology, Bombay (IITB) Powai, Mumbai
— On Wed, 11/10/10, Markus Neteler [via OSGeo.org] <[hidden email]> wrote:
> From: Markus Neteler [via OSGeo.org] <[hidden email]> > Subject: Re: Need some help in converting a contour map to DEM map… > To: “nikmor” <[hidden email]> > Date: Wednesday, November 10, 2010, 2:00 PM > > On Tue, Nov 9, 2010 at 12:28 PM, nikmor <[hidden email]> wrote: > > > > Hello friends > > > > I am trying to import an contour file and trying to come up with an DEM map > > from it. I tried it my way but end up with wrong output. I am looking > > forward for some one who can import this map and convert it to DEM and > > finally and most importantly we should be able to view the output in NVIZ. I > > have attached the folder having the contour data, this data is of IIT > > bombay. > > Please take a look here. > http://grass.osgeo.org/wiki/Contour_lines_to_DEM > > Markus > _______________________________________________ > grass-user mailing list > [hidden email] > http://lists.osgeo.org/mailman/listinfo/grass-user > > — > > View message @ http://osgeo-org.1803224.n2.nabble.com/Need-some-help-in-converting-a-contour-map-to-DEM-map-tp5720519p5723857.html > To unsubscribe from Need some help in converting a contour map to DEM map…, click here.
thanks for the link. I have tried it out and it works with v.surf.rst. But when I use r.surf.contour it takes a very very long time and it never ends. I would be thankful if you could suggest me something regarding the resolution(grid resolution 2d in g.region modules resolution tab). |
|
You can set the resolution to whatever you want. But choosing a reasonable resolution depends on your source data and how large an area you are working with. The contour lines you sent were at 5 m spacing, and the area seems to be only 0.02 deg ~= 2 km. So you can try a small resolution, such as 1 meter. So if you run (from the command line)
g.region vect=contour res=0:00:00.03 -p
This should set the region to the extent of the contour vector, and resolution to 3/100 arcsec or about 1 meter. Your raster will be about 2000X2500 ( ~ 5,000,000 cells), and any modern computer can do raster operations on that size in a reasonable time.
···
--
Micha Silver
[http://www.surfaces.co.il/](http://www.surfaces.co.il/)
Arava Development Co. +972-52-3665918
I am very thankful to all who helped me, I have got the correct output after
setting the resolution and running v.surf.rst. I am attaching the nviz view
of the DEM after exagerating it.Now I am looking forward to drape an aerial
image of the same area on the DEM that I have got. In order to do this I
loaded the DEM map and then draped the imported aerial map (imported using
r.in.gdal, but that single jpeg image(satimage.jpg) got imported into 3
different maps namely satimage.red, satimage.green, satimage.blue, therefore
is just draped only one of it on the DEM). The output view that I get seems
okay but its too dark (black and white-- please see the attachment), though
the original aerial image was colourful which I had imported. Why is it
happening so?? Can any one help me with this.
of the DEM after exagerating it.Now I am looking forward to drape an aerial
image of the same area on the DEM that I have got. In order to do this I
loaded the DEM map and then draped the imported aerial map (imported using
r.in.gdal, but that single jpeg image(satimage.jpg) got imported into 3
different maps namely satimage.red, satimage.green, satimage.blue, therefore
is just draped only one of it on the DEM). The output view that I get seems
okay but its too dark (black and white-- please see the attachment), though
the original aerial image was colourful which I had imported. Why is it
happening so?? Can any one help me with this.
Visualizing (true) color composites
To quickly combine the first three channels to a near natural color image, the GRASS command d.rgb can be used or the graphical GIS manager (gis.m). It assigns each channel to a color which is then mixed while displayed. With a bit more work of tuning the grey scales of the channels, nearly perfect colors can be achieved. Channel histograms can be shown with d.histogram.
Thanks for the link. I finally got the coloured aerial image draped on the
DEM map and which can be viewed in nviz. Since the aerial image was getting
imported in an rgb files (3 different files) I first needed to combine them
into one raster map, which could be done using r.composite. which takes in
these 3 files (.red, .green, .blue) and one output map name of users choice.
Thanks once again for your help sir.
I have a LANDSAT image imported in my mapset using r.in.gdal. I used
r.composite to combine the rgb files. After all these, now if I wants to get
the pixel value on click of a mouse on the raster map. Is it possible for me
to somehow get the pixel value (that is red, blue and green color values
which should lie within 0-255 range) on click. I need some help.
I have a LANDSAT image imported in my mapset using r.in.gdal. I used
r.composite to combine the rgb files. After all these, now if I wants to get
the pixel value on click of a mouse on the raster map. Is it possible for me
to somehow get the pixel value (that is red, blue and green color values
which should lie within 0-255 range) on click. I need some help.
Yes, *before* you combine the bands. If you select one band and use the query button in the GUI interface, you'll get the pixel value of that band at the click location.
