[GRASS-user] Help combining raster and vector data into single raster image

GRASS GRASS user
,
1

I am currently trying to take a raster map and a vector map and combine them to produce a raster (image) map. I am running GRASS 6.1.0 on an Intel Mac and have tried several different avenues, none to any success. If anyone has any successful experience with any of the following methods, I would greatly appreciate any help you could provide.

1. First tried displaying everything in the "Map Display" window, saving this image as a TIFF, JPG, BMP, and/or a PPM, and then importing this image using r.in.gdal.
   In every case, the output image looks fine, but r.in.gdal imports the three bands (red, green, blue or 1, 2, 3) as empty files. At least, when I display the files, there is nothing there. I tried combining the three bands into a single RGB raster using r.composite, and also tried overriding the projection on import in case there was a problem with that, but neither trick worked. Is there something I am missing here?

2. Also tried using the regular display monitor with the PNG driver to save a PNG file. Similar problem, as I can produce the png file, but when I import this into Grass, it again is an empty file. I would like to use the CELL driver (per Grass 5 documentation), but this feature must have been removed from Grass 6, because it is not listed as a valid display monitor with d.mon -l and when I try the command "d.mon start=CELL" it says there is no such monitor as 'CELL'.

3. I also tried to get around the apparent r.in.gdal problem by using gdal_translate to translate the various image files (TIFF, JPG, etc) into an ArcInfo ASCII grid and then import this into Grass using r.in.arc. While gdal_translate writes the Arcinfo grid sucessfully, trying to import this file in grass using r.in.arc results in the following error:
r.in.arc: ** errors detected in header section **

   illegal line in header
   dx 1.000000000000
   "cellsize" field missing from header
   "nodata_value" field missing from header
ERROR: Can't get cell header

Does anyone what I am doing wrong in any of these methods (it is very likely I am missing something, I've only been using grass for a couple of weeks)? Or have any tips on how to accomplish what I want to produce?

Thanks in advance for any advice.

Romy

2

Romy Schneider wrote:

I am currently trying to take a raster map and a vector map and
combine them to produce a raster (image) map. I am running GRASS
6.1.0 on an Intel Mac and have tried several different avenues, none
to any success. If anyone has any successful experience with any of
the following methods, I would greatly appreciate any help you could
provide.

1. First tried displaying everything in the "Map Display" window,
saving this image as a TIFF, JPG, BMP, and/or a PPM, and then
importing this image using r.in.gdal.
   In every case, the output image looks fine, but r.in.gdal imports
the three bands (red, green, blue or 1, 2, 3) as empty files. At
least, when I display the files, there is nothing there. I tried
combining the three bands into a single RGB raster using r.composite,
and also tried overriding the projection on import in case there was
a problem with that, but neither trick worked. Is there something I
am missing here?

Images are normally imported at the origin of the coordinate system,
which results in them lying outside of the current region. Check the
maps' bounds with r.info; you can fix the bounds with r.region.

In any case, this is usually the wrong approach. Rendering maps
introduces resampling errors and loss of georeferencing.

2. Also tried using the regular display monitor with the PNG driver
to save a PNG file. Similar problem, as I can produce the png file,
but when I import this into Grass, it again is an empty file.

This is essentially the same process as #1, except doing it manually
instead of having gis.m/d.m doing it for you. It suffers from all of
the same issues as #1.

I would like to use the CELL driver (per Grass 5 documentation), but
this feature must have been removed from Grass 6, because it is not
listed as a valid display monitor with d.mon -l and when I try the
command "d.mon start=CELL" it says there is no such monitor as 'CELL'.

The CELL driver is no longer supported. It wouldn't eliminate the
problems you are having.

3. I also tried to get around the apparent r.in.gdal problem by
using gdal_translate to translate the various image files (TIFF, JPG,
etc) into an ArcInfo ASCII grid and then import this into Grass using
r.in.arc. While gdal_translate writes the Arcinfo grid sucessfully,
trying to import this file in grass using r.in.arc results in the
following error:
r.in.arc: ** errors detected in header section **

   illegal line in header
   dx 1.000000000000
   "cellsize" field missing from header
   "nodata_value" field missing from header
ERROR: Can't get cell header

I'm not familiar enough with ArcInfo files to comment on this.

Does anyone what I am doing wrong in any of these methods (it is very
likely I am missing something, I've only been using grass for a
couple of weeks)? Or have any tips on how to accomplish what I want
to produce?

To combine several maps, first convert the vectors to rasters with
v.to.rast, then patch the raster maps together with r.patch.

In general, re-importing images generated by the d.* commands and the
PNG driver is almost always the wrong approach.

--
Glynn Clements <glynn@gclements.plus.com>

3

Romy,

Try this...

-Use v.to.rast to create a rasterized version of your vector map. Make sure
that the areas between the vectors are Null (use r.null as needed)

-Use r.colors (and r.reclass/r.recode as needed) to make sure that the
vector items are the proper color.

-Use r.patch to fill in the null areas between the vectors with your raster
map, creating a new map with the rasters and vectors in a single raster
image.

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics and Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

From: Romy Schneider <romy@tacc.utexas.edu>
Date: Mon, 25 Sep 2006 14:25:15 -0500
To: <grassuser@grass.itc.it>
Subject: [GRASS-user] Help combining raster and vector data into single raster
image

I am currently trying to take a raster map and a vector map and
combine them to produce a raster (image) map. I am running GRASS
6.1.0 on an Intel Mac and have tried several different avenues, none
to any success. If anyone has any successful experience with any of
the following methods, I would greatly appreciate any help you could
provide.

1. First tried displaying everything in the "Map Display" window,
saving this image as a TIFF, JPG, BMP, and/or a PPM, and then
importing this image using r.in.gdal.
   In every case, the output image looks fine, but r.in.gdal imports
the three bands (red, green, blue or 1, 2, 3) as empty files. At
least, when I display the files, there is nothing there. I tried
combining the three bands into a single RGB raster using r.composite,
and also tried overriding the projection on import in case there was
a problem with that, but neither trick worked. Is there something I
am missing here?

2. Also tried using the regular display monitor with the PNG driver
to save a PNG file. Similar problem, as I can produce the png file,
but when I import this into Grass, it again is an empty file. I
would like to use the CELL driver (per Grass 5 documentation), but
this feature must have been removed from Grass 6, because it is not
listed as a valid display monitor with d.mon -l and when I try the
command "d.mon start=CELL" it says there is no such monitor as 'CELL'.

3. I also tried to get around the apparent r.in.gdal problem by
using gdal_translate to translate the various image files (TIFF, JPG,
etc) into an ArcInfo ASCII grid and then import this into Grass using
r.in.arc. While gdal_translate writes the Arcinfo grid sucessfully,
trying to import this file in grass using r.in.arc results in the
following error:
r.in.arc: ** errors detected in header section **

   illegal line in header
   dx 1.000000000000
   "cellsize" field missing from header
   "nodata_value" field missing from header
ERROR: Can't get cell header

Does anyone what I am doing wrong in any of these methods (it is very
likely I am missing something, I've only been using grass for a
couple of weeks)? Or have any tips on how to accomplish what I want
to produce?

Thanks in advance for any advice.

Romy