[GRASS-user] assign heigght value to pixel(x,y)

vinod_kumar · April 14, 2011, 12:33pm

Hi all,

how to assign height value(z) to a particular pixel having x and y coordinates in an orthphoto using grass.

Thanks in advance,
nani

Daniel_Victoria · April 16, 2011, 3:21pm

Maybe d.rast.edit? never done it myself, just noticed the command on
the raster manual and don't even know how it works...

On Thu, Apr 14, 2011 at 9:33 AM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi all,

how to assign height value(z) to a particular pixel having x and y
coordinates in an orthphoto using grass.

Thanks in advance,
nani

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vinod_kumar · April 16, 2011, 5:23pm

Hi Daniel Victoria,

d.rast.edit is to edit the raster data and i want to know how to assign ‘Z’ value or height value to a particular pixel(x,y) and this would be helpful if there is an automatic algorithm for assigning height value for selected pixels.

Thanks,
nani.

On Sat, Apr 16, 2011 at 8:21 AM, Daniel Victoria <daniel.victoria@gmail.com> wrote:

Maybe d.rast.edit? never done it myself, just noticed the command on
the raster manual and don’t even know how it works…

On Thu, Apr 14, 2011 at 9:33 AM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi all,

how to assign height value(z) to a particular pixel having x and y
coordinates in an orthphoto using grass.

Thanks in advance,
nani

grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

neteler · April 16, 2011, 5:26pm

On Sat, Apr 16, 2011 at 7:23 PM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Daniel Victoria,

d.rast.edit is to edit the raster data and i want to know how to assign 'Z'
value or height value to a particular pixel(x,y) and this would be helpful
if there is an automatic algorithm for assigning height value for selected
pixels.

The easiest way is:
- import pixel with r.in.ascii
- patch into existing raster map with r.patch

Markus

vinod_kumar · April 16, 2011, 8:36pm

Hi Markus Neteler,

yes, importing pixel values with r.in ascii and patch into existing into raster is simple easy for particular pixel,
but if we want to assign a height value to more pixels, for example assigning height value to buildings in a
particular area in raster map is difficult as we don’t no to which pixel value we have to assign height value and
checking each pixel value is difficult. And i am more intrested by doing automatic process.

Thanks in advance,
nani.

On Sat, Apr 16, 2011 at 10:26 AM, Markus Neteler <neteler@osgeo.org> wrote:

On Sat, Apr 16, 2011 at 7:23 PM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Daniel Victoria,

d.rast.edit is to edit the raster data and i want to know how to assign ‘Z’
value or height value to a particular pixel(x,y) and this would be helpful
if there is an automatic algorithm for assigning height value for selected
pixels.

The easiest way is:

import pixel with r.in.ascii

patch into existing raster map with r.patch

Markus

neteler · April 17, 2011, 6:06am

On Sat, Apr 16, 2011 at 10:36 PM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Markus Neteler,

yes, importing pixel values with r.in ascii and patch into existing into
raster is simple easy for particular pixel,
but if we want to assign a height value to more pixels, for example
assigning height value to buildings in a
particular area in raster map is difficult as we don't no to which pixel
value we have to assign height value and
checking each pixel value is difficult.

Now I understand a bit more: so use r.mapcalc with an if() condition.

Markus

vinod_kumar · April 17, 2011, 2:16pm

Hi Markus Netler,

Using r.mapcalc with an if() condition might work but how can we give a condition without knowing anything about pixels(like… where it is located and height… etc).
i am doing this for to assign height values to some pixels where i do not know the buildings location in a raster map graphically.

I think we are on the way to the solution. next step would be the solution.

thanks,
nani.

On Sun, Apr 17, 2011 at 8:06 AM, Markus Neteler <neteler@osgeo.org> wrote:

On Sat, Apr 16, 2011 at 10:36 PM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Markus Neteler,

yes, importing pixel values with r.in ascii and patch into existing into
raster is simple easy for particular pixel,
but if we want to assign a height value to more pixels, for example
assigning height value to buildings in a
particular area in raster map is difficult as we don’t no to which pixel
value we have to assign height value and
checking each pixel value is difficult.

Now I understand a bit more: so use r.mapcalc with an if() condition.

Markus

vinod_kumar · April 17, 2011, 7:57pm

Hi Markus Netler,

i want to identify buildings, trees etc… and assign height values at particular zoom level in a raster map and to view the data in a 3Dimensional where i do not have any information to identify pixel graphically.

And the problem also persists in identifying buildings and assigning height values and to use condition like IF might not be possible as there is no source of information.

Thanks in advance,
nani.

On Sat, Apr 16, 2011 at 11:06 PM, Markus Neteler <neteler@osgeo.org> wrote:

On Sat, Apr 16, 2011 at 10:36 PM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Markus Neteler,

yes, importing pixel values with r.in ascii and patch into existing into
raster is simple easy for particular pixel,
but if we want to assign a height value to more pixels, for example
assigning height value to buildings in a
particular area in raster map is difficult as we don’t no to which pixel
value we have to assign height value and
checking each pixel value is difficult.

Now I understand a bit more: so use r.mapcalc with an if() condition.

Markus

Sylvain_Maillard · April 17, 2011, 8:56pm

Hi,

i’m not sure that the raster way is the easiest, the tools are not really usable for what you want to do …

you better have to make a new vector layer with a “height” attribute, then display it over your raster and edit the vector layer by drawing polygon/point with the height as attibute. Once ended, you will have to convert the vector to raster (v.to.rast) using the attribute “height” as raster value.
I think it’s the easiest way as you will be able to store the same height for many consecutive pixel without having to edit each one, and you will also be able to easily change the height if your first try is not good enought

cheers,

Sylvain

2011/4/17 vinod kumar <nani.kunithi@gmail.com>

Hi Markus Netler,

i want to identify buildings, trees etc… and assign height values at particular zoom level in a raster map and to view the data in a 3Dimensional where i do not have any information to identify pixel graphically.

And the problem also persists in identifying buildings and assigning height values and to use condition like IF might not be possible as there is no source of information.

Thanks in advance,
nani.

On Sat, Apr 16, 2011 at 11:06 PM, Markus Neteler <neteler@osgeo.org> wrote:

On Sat, Apr 16, 2011 at 10:36 PM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Markus Neteler,

yes, importing pixel values with r.in ascii and patch into existing into
raster is simple easy for particular pixel,
but if we want to assign a height value to more pixels, for example
assigning height value to buildings in a
particular area in raster map is difficult as we don’t no to which pixel
value we have to assign height value and
checking each pixel value is difficult.

Now I understand a bit more: so use r.mapcalc with an if() condition.

Markus

grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

vinod_kumar · April 18, 2011, 7:13am

Hi Sylvain Maillard,

Thanks for providing the information on creating separating vector layer to assign height but how to make 3Dimensional layer for the raster with accurate weightage value to each pixel.

Thanks in advance,
nani

On Sun, Apr 17, 2011 at 10:56 PM, Sylvain Maillard <sylvain.maillard@gmail.com> wrote:

Hi,

i’m not sure that the raster way is the easiest, the tools are not really usable for what you want to do …

you better have to make a new vector layer with a “height” attribute, then display it over your raster and edit the vector layer by drawing polygon/point with the height as attibute. Once ended, you will have to convert the vector to raster (v.to.rast) using the attribute “height” as raster value.
I think it’s the easiest way as you will be able to store the same height for many consecutive pixel without having to edit each one, and you will also be able to easily change the height if your first try is not good enought

cheers,

Sylvain

2011/4/17 vinod kumar <nani.kunithi@gmail.com>

Hi Markus Netler,

i want to identify buildings, trees etc… and assign height values at particular zoom level in a raster map and to view the data in a 3Dimensional where i do not have any information to identify pixel graphically.

And the problem also persists in identifying buildings and assigning height values and to use condition like IF might not be possible as there is no source of information.

Thanks in advance,
nani.

On Sat, Apr 16, 2011 at 11:06 PM, Markus Neteler <neteler@osgeo.org> wrote:

On Sat, Apr 16, 2011 at 10:36 PM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Markus Neteler,

yes, importing pixel values with r.in ascii and patch into existing into
raster is simple easy for particular pixel,
but if we want to assign a height value to more pixels, for example
assigning height value to buildings in a
particular area in raster map is difficult as we don’t no to which pixel
value we have to assign height value and
checking each pixel value is difficult.

Now I understand a bit more: so use r.mapcalc with an if() condition.

Markus

grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

Stefan1 · April 19, 2011, 11:11am

nani,

have a look at:

http://grass.osgeo.org/grass64/manuals/html64_user/v.extrude.html

stefan

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vinod_kumar · April 19, 2011, 12:35pm

Hi Sylvain Maillard,

It means that we cannot obtain 3d from raster (orthophoto) and for that we need to build block of data in a 3Dimensional using some graphic software , right?

One more question, i am not having vector layer and i need to create from raster and intrestingly i am having cadastral layer with attributes(height of buildings).

So i am planning to create grid, triangulate and assign heights to the buildings.

And with cadastral data information and raster data, can we create DTM and export those values into VRML or X3d formats.

Thanks in advance,
nani.

On Mon, Apr 18, 2011 at 9:13 AM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Sylvain Maillard,

Thanks for providing the information on creating separating vector layer to assign height but how to make 3Dimensional layer for the raster with accurate weightage value to each pixel.

Thanks in advance,
nani

On Sun, Apr 17, 2011 at 10:56 PM, Sylvain Maillard <sylvain.maillard@gmail.com> wrote:

Hi,

i’m not sure that the raster way is the easiest, the tools are not really usable for what you want to do …

you better have to make a new vector layer with a “height” attribute, then display it over your raster and edit the vector layer by drawing polygon/point with the height as attibute. Once ended, you will have to convert the vector to raster (v.to.rast) using the attribute “height” as raster value.
I think it’s the easiest way as you will be able to store the same height for many consecutive pixel without having to edit each one, and you will also be able to easily change the height if your first try is not good enought

cheers,

Sylvain

2011/4/17 vinod kumar <nani.kunithi@gmail.com>

Hi Markus Netler,

i want to identify buildings, trees etc… and assign height values at particular zoom level in a raster map and to view the data in a 3Dimensional where i do not have any information to identify pixel graphically.

And the problem also persists in identifying buildings and assigning height values and to use condition like IF might not be possible as there is no source of information.

Thanks in advance,
nani.

On Sat, Apr 16, 2011 at 11:06 PM, Markus Neteler <neteler@osgeo.org> wrote:

On Sat, Apr 16, 2011 at 10:36 PM, vinod kumar <nani.kunithi@gmail.com> wrote:

Hi Markus Neteler,

yes, importing pixel values with r.in ascii and patch into existing into
raster is simple easy for particular pixel,
but if we want to assign a height value to more pixels, for example
assigning height value to buildings in a
particular area in raster map is difficult as we don’t no to which pixel
value we have to assign height value and
checking each pixel value is difficult.

Now I understand a bit more: so use r.mapcalc with an if() condition.

Markus

grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user