[GRASS-user] Re: QGIS GRASS plugin shadedrelief issue

nunosousa84 nuno_sousa_1984 at hotmail.com
Mon Sep 20 06:32:18 EDT 2010

Thank you all. Well i have some news. Hamish i have followed your suggestion
of using the mapcalc commands. For all this steps i worked directly through
GRASS 6.4 0RC6 and not QGIS. I have opened the grass raster layer with the
contours (lines) and applyed the commands suggested:
The result was this:
Well it seems the terrace effect desappeared but there are some glintches,
do you think its normal?
Concerning the flat mesa tops they look really ugly, any suggestion how to
remake/remodel them? I suppose i have to go to the original geotiff
topography chart and remake some vector lines to overcome that problem? What
should i do?

About the blackspots and the color table im not sure but changing it doesnt
overcome the problem, the spots remain the same. Here it is the r.univar
report of the shadedrelief layer:

"total null and non-null cells: 2256660

total null cells: 6164

Of the non-null cells:


n: 2250496

minimum: -75.1119

maximum: 100

range: 175.112

mean: 42.1701

mean of absolute values: 48.816

standard deviation: 35.304

variance: 1246.37

variation coefficient: 83.718 %

sum: 94903752.6220222563"

Now to the strange issue (QGIS Shaded Relief Plugin). Remember the error i
posted earlier? Well it seems i was able to work with that plugin but only
after i run the surf contour layer in GRASS. Let me explain i redone the
steps decribed before as suggested by Hamish (mapcalc, surfcontour,etc...),
all in GRASS 6.4 0RC6. Then changed to QGIS, opened the layer just made in
GRASS and run the QGIS Shaded Relief Plugin. Now it worked.
About the Region Settings they were set in QGIS. Since the region im working
is fairly small i used this parameters: N-S Res = 1.00014 and E-W Res =
1.00024 (I think this is the minimum resolution supported). One problem i
noticed and it might be a QGIS bug is that everytime i open QGIS or add a
layer it resets the projection/coordination values (For example im using
Datum ED50 UTM zone 29 international ellipsoid but when i open a layer or
QGIS it always resets this values to others). Maybe i should save this
parameters directly in GRASS? My dificulty is how, there are so many
commands for a begginer :-)

Regards and thank you

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