[GRASS-user] Low map display resolution in default 6.4 ?

GRASS GRASS user
1

Hello,

Since I compiled latest 6.4RC5 Grass version, I experienced
significative speed gain when displaying DEM raster levels - at the
expense of the displayed resolution: the whole thing just looks
"soappy", and keeps getting worse once you zoom in. With my previous
version (6.23), the same raster display opreration (d.rast) took
forever, but I had the possibility to control data errors at the
finest level. So surely there must be an option I don't know yet to
increase the resolution of the Map display windows; it would be very
nice if somebody could explain me how it works.

Thanks for your help,

Felix

2

Felix Schalck:

Since I compiled latest 6.4RC5 Grass version, I experienced
significative speed gain when displaying DEM raster levels - at the
expense of the displayed resolution: the whole thing just looks
"soappy", and keeps getting worse once you zoom in. With my previous
version (6.23), the same raster display opreration (d.rast) took
forever, but I had the possibility to control data errors at the
finest level. So surely there must be an option I don't know yet to
increase the resolution of the Map display windows; it would be very
nice if somebody could explain me how it works.

Hi Felix!

What is the resolution of your DEM?
Did you set it using "g.region"?
Are you interested in (only) displaying or (in addition in) processing
your DEM at high-resolution?

.

If you are new in GRASS-GIS then its worthy to read the intro(s) [1][2].
Perhaps you are looking info on how to set the resolution which is done
with the module "g.region"[3]. ( Note that "g.region" != "r.region" )

Apologies if you are familiar with all this, Nikos
---

[1] http://grass.osgeo.org/grass64/manuals/html64_user/helptext.html
[2] http://grass.osgeo.org/grass64/manuals/html64_user/rasterintro.html
[3] http://grass.osgeo.org/grass64/manuals/html64_user/g.region.html

3

Dear Nikos,

Many thanks for your reply. But even before listing up the requested
data, please noticed that, basically, I didn't change any settings
(g.region) when upgrading to 6.4: I just compiled and installed the
new version, and now everthing I loaded in 6.23 looks "soappy" in 6.4.
Resolution is important for both live display in GRASS, to control
data elevation errors, and further processing, since the final pgn map
should be exported at the highest possible resolution.

As of the requested additionnal data, here you go:

1. DEM resolution:
$gdalinfo srtm_38_03.tif

Driver: GTiff/GeoTIFF
Files: srtm_38_03.tif
Size is 6000, 6000
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.2572235630016,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (5.000000000000000,50.000000000000000)
Pixel Size = (0.000833333333333,-0.000833333333333)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 5.0000000, 50.0000000) ( 5d 0'0.00"E, 50d 0'0.00"N)
Lower Left ( 5.0000000, 45.0000000) ( 5d 0'0.00"E, 45d 0'0.00"N)
Upper Right ( 10.0000000, 50.0000000) ( 10d 0'0.00"E, 50d 0'0.00"N)
Lower Right ( 10.0000000, 45.0000000) ( 10d 0'0.00"E, 45d 0'0.00"N)
Center ( 7.5000000, 47.5000000) ( 7d30'0.00"E, 47d30'0.00"N)
Band 1 Block=6000x1 Type=Int16, ColorInterp=Gray
  NoData Value=-32768

2. Region settings:
$g.region -p

projection: 3 (Latitude-Longitude)
zone: 0
datum: wgs84
ellipsoid: wgs84
north: 60N
south: 34N
west: 11W
east: 35E
nsres: 0:00:03
ewres: 0:00:03
rows: 31200
cols: 55200
cells: 1722240000

If I interpret those numbers correctly, the region is set to the
theoretical max. resolution. Again, since I basically did not touch
the configs during the upgrade procedure (GRASS 6.23>6.4RC5) I thought
to myself it might just be a configuration change of the default
driver used by d.rast: in the old version, it took forever to load,
but the level of details SEEMED much higher, now it loads quasi
instantly, but looks 'soappy'. What changed ?

Regards,

Felix

2009/8/14 Nikos Alexandris <nikos.alexandris@felis.uni-freiburg.de>:

Felix Schalck:

Since I compiled latest 6.4RC5 Grass version, I experienced
significative speed gain when displaying DEM raster levels - at the
expense of the displayed resolution: the whole thing just looks
"soappy", and keeps getting worse once you zoom in. With my previous
version (6.23), the same raster display opreration (d.rast) took
forever, but I had the possibility to control data errors at the
finest level. So surely there must be an option I don't know yet to
increase the resolution of the Map display windows; it would be very
nice if somebody could explain me how it works.

Hi Felix!

What is the resolution of your DEM?
Did you set it using "g.region"?
Are you interested in (only) displaying or (in addition in) processing
your DEM at high-resolution?

.

If you are new in GRASS-GIS then its worthy to read the intro(s) [1][2].
Perhaps you are looking info on how to set the resolution which is done
with the module "g.region"[3]. ( Note that "g.region" != "r.region" )

Apologies if you are familiar with all this, Nikos
---

[1] http://grass.osgeo.org/grass64/manuals/html64_user/helptext.html
[2] http://grass.osgeo.org/grass64/manuals/html64_user/rasterintro.html
[3] http://grass.osgeo.org/grass64/manuals/html64_user/g.region.html

4

Hi Felix,

On Fri, Aug 14, 2009 at 11:43 PM, Felix Schalck<felix.schalck@gmail.com> wrote:
...

1. DEM resolution:
$gdalinfo srtm_38_03.tif

...

Pixel Size = (0.000833333333333,-0.000833333333333)

...

2. Region settings:
$g.region -p

...

nsres: 0:00:03
ewres: 0:00:03

which corresponds to:

g.region -g
...
nsres=0.000833333333333331
ewres=0.000833333333333333

That should be fine, but...

If I interpret those numbers correctly, the region is set to the
theoretical max. resolution. Again, since I basically did not touch
the configs during the upgrade procedure (GRASS 6.23>6.4RC5) I thought
to myself it might just be a configuration change of the default
driver used by d.rast: in the old version, it took forever to load,
but the level of details SEEMED much higher, now it loads quasi
instantly, but looks 'soappy'. What changed ?

(nothing should have changed)

... did you use d.erase to tell the GRASS monitor about the high
resolution? The technology behind all is still the same in 6.4.

Markus

5

Markus Neteler wrote:

Hi Felix,

On Fri, Aug 14, 2009 at 11:43 PM, Felix Schalck<felix.schalck@gmail.com> wrote:
...
  

1. DEM resolution:
$gdalinfo srtm_38_03.tif
    

...
  

Pixel Size = (0.000833333333333,-0.000833333333333)
    

...
  

2. Region settings:
$g.region -p
    

...
  

nsres: 0:00:03
ewres: 0:00:03
    
which corresponds to:

g.region -g
...
nsres=0.000833333333333331
ewres=0.000833333333333333

That should be fine, but...

If I interpret those numbers correctly, the region is set to the
theoretical max. resolution. Again, since I basically did not touch
the configs during the upgrade procedure (GRASS 6.23>6.4RC5) I thought
to myself it might just be a configuration change of the default
driver used by d.rast: in the old version, it took forever to load,
but the level of details SEEMED much higher, now it loads quasi
instantly, but looks 'soappy'. What changed ?
    
(nothing should have changed)

... did you use d.erase to tell the GRASS monitor about the high
resolution? The technology behind all is still the same in 6.4.
Markus
  
d.erase ? Not at all...

I'm really sorry I have no screenshot to show you the difference - since now, when starting 6.23, I'm getting the same high speed-low-res-display. Nonetheless, the loading time alone is a good change-marker, proving that, at least on my machine, something is different now. I'm going to check out the default Ubuntu .deb configuration of GRASS 6.23, and look if something is missing in my own compilation of 6.4.

In the end, perhaps something was broken in the old version (it took really forever to load even one cgiar srtm tile alone) which has been fixed now !

Thank you very much for your patience,

Felix

6

Felix wrote:

2. Region settings:
$g.region -p

projection: 3 (Latitude-Longitude)

....

nsres: 0:00:03
ewres: 0:00:03
rows: 31200
cols: 55200
cells: 1722240000

unless you have some very large monitor, I would suggest to
set the resolution to say 0:01 for display purposes.

g.region res=0:01 -ap

raise it again if you need to do processing.

64 bit computer? or was it compiled with large file support?
(your region is huge)

what does r.univar say about it?

Hamish

7

Felix wrote:

Driver: GTiff/GeoTIFF
Files: srtm_38_03.tif
Size is 6000, 6000

....

2. Region settings:
$g.region -p
rows: 31200
cols: 55200

rows, cols to not match.

try 'g.region rast=your_imported_raster_map'

Hamish

8

After some research, I figured out that:

1) Resolution is not really the problem, since I added a shadings
layer which shows the same impressive details level than I used to
have in old 6.23. It is really a display question.

2) Perhaps it is the graphic driver. I did not yet found the
./configure summary of the default ubuntu GRASS .deb, but I really
doubt that it is built against latest proprietary nvidia 64bits OpenGL
libs - which I did in my own compilation of 6.4RC5. Fact is that
display has changed for all GRASS operations (not only d.rast), and
even though the new display doesn't LOOK very sharp, the levels of
details is just the same, but with an impressive gain in speed.

What do you think ?

Felix

2009/8/15 Hamish <hamish_b@yahoo.com>:

Felix wrote:

Driver: GTiff/GeoTIFF
Files: srtm_38_03.tif
Size is 6000, 6000

....

2. Region settings:
$g.region -p
rows: 31200
cols: 55200

rows, cols to not match.

try 'g.region rast=your_imported_raster_map'

Hamish

9

On 16/08/09 21:48, Felix Schalck wrote:

After some research, I figured out that:

1) Resolution is not really the problem, since I added a shadings
layer which shows the same impressive details level than I used to
have in old 6.23. It is really a display question.

2) Perhaps it is the graphic driver. I did not yet found the
./configure summary of the default ubuntu GRASS .deb, but I really
doubt that it is built against latest proprietary nvidia 64bits OpenGL
libs - which I did in my own compilation of 6.4RC5. Fact is that
display has changed for all GRASS operations (not only d.rast), and
even though the new display doesn't LOOK very sharp, the levels of
details is just the same, but with an impressive gain in speed.

What do you think ?

What do you use to display you maps ? If you use the GUI, note that the GUI does not necessarily display in the current working resolution, but often downgrades resolution for display in order to make it faster. However, you can constrain the display to your computational region's resolution.

You should see no difference in display if you use x-monitors (i.e. launched with d.mon. My memories are a bit weak of that time (long ago), but I think that the 6.2 GUI still used x-monitors for display. This has changed since.

Moritz

10

2009/8/17 Moritz Lennert <mlennert@club.worldonline.be>:

On 16/08/09 21:48, Felix Schalck wrote:

After some research, I figured out that:

1) Resolution is not really the problem, since I added a shadings
layer which shows the same impressive details level than I used to
have in old 6.23. It is really a display question.

2) Perhaps it is the graphic driver. I did not yet found the
./configure summary of the default ubuntu GRASS .deb, but I really
doubt that it is built against latest proprietary nvidia 64bits OpenGL
libs - which I did in my own compilation of 6.4RC5. Fact is that
display has changed for all GRASS operations (not only d.rast), and
even though the new display doesn't LOOK very sharp, the levels of
details is just the same, but with an impressive gain in speed.

What do you think ?

What do you use to display you maps ? If you use the GUI, note that the GUI
does not necessarily display in the current working resolution, but often
downgrades resolution for display in order to make it faster.

That's was exactly my question: so GUI (I use wxpython interface) DEOS
resampling to fasten dispay operations !

However, you
can constrain the display to your computational region's resolution.

How do you do that ?

You should see no difference in display if you use x-monitors (i.e. launched
with d.mon. My memories are a bit weak of that time (long ago), but I think
that the 6.2 GUI still used x-monitors for display. This has changed since.

Moritz

11

Moritz wrote:

You should see no difference in display if you use
x-monitors (i.e. launched with d.mon. My memories are a bit
weak of that time (long ago), but I think that the 6.2 GUI
still used x-monitors for display. This has changed since.

Xmonitors + d.mon are still present in all GRASS 6.x, but they are removed
in grass7. What changed is that the old d.m tcl/tk GUI used them but the
new gis.m tcl/tk GUI does not.

for some things like r.digit and i.ortho.photo they are still required.

use them every day,
Hamish

12

On 17/08/09 12:05, Hamish wrote:

Moritz wrote:

You should see no difference in display if you use
x-monitors (i.e. launched with d.mon. My memories are a bit
weak of that time (long ago), but I think that the 6.2 GUI
still used x-monitors for display. This has changed since.

Xmonitors + d.mon are still present in all GRASS 6.x, but they are removed
in grass7. What changed is that the old d.m tcl/tk GUI used them but the
new gis.m tcl/tk GUI does not.

Yes, and I can't remember when the change from one GUI to the other (as default) happened...

Moritz