[GRASSLIST:9648] Import Gridded Population of the World

GRASS GRASS user
1

Hello,

I tried to import the raster files of gpw (*bil etc.). The import via r.in.gdal runs without errors but the resulting raster is empty (just zero values).

Is this a known problem ?

Thanks in advance

Karl Broich

--------------------------------------------------------------------------
Dr.-Ing. Karl BROICH Tel: +49 / (0) 89 / 6004 2478
Universität der Bundeswehr München Fax: +49 / (0) 89 / 6004 3858
Institut für Wasserwesen
Werner-Heisenberg-Weg 39
D 85577 Neubiberg
--------------------------------------------------------------------------

2

Karl,

did you zoom to the map?

g.region rast=gpw -p

Then you may check the statistics (probably just the color
table is non-representative):

r.univar gpw

If everything is still zero, please let us know.

Markus

On Tue, Dec 27, 2005 at 05:06:55PM +0100, Karl Broich wrote:

Hello,

I tried to import the raster files of gpw (*bil etc.). The import via
r.in.gdal runs without errors but the resulting raster is empty (just zero
values).

Is this a known problem ?

Thanks in advance

Karl Broich

--------------------------------------------------------------------------
Dr.-Ing. Karl BROICH Tel: +49 / (0) 89 / 6004 2478
Universität der Bundeswehr München Fax: +49 / (0) 89 / 6004 3858
Institut für Wasserwesen
Werner-Heisenberg-Weg 39
D 85577 Neubiberg
--------------------------------------------------------------------------

--
Markus Neteler <neteler itc it> http://mpa.itc.it
ITC-irst - Centro per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
Via Sommarive, 18 - 38050 Povo (Trento), Italy

3

Karl,

[ after having received offlist the data]
ok.

the problem is that GRASS by default applies
a linear color table. However, with the megacities
in Asia and elsewhere, this doesn't quite work

the solution is to apply a custom color table,
or, as a first approach, a logarithmic table

r.colors asds00gialpha1 col=grey.log
d.rast asds00gialpha1

Works :slight_smile:

Markus

On Wed, Dec 28, 2005 at 03:42:42PM +0100, Karl Broich wrote:

Markus,

At 11:23 28.12.2005 +0100, you wrote:
>Karl,
>
>did you zoom to the map?

no.

>g.region rast=gpw -p
>
>Then you may check the statistics (probably just the color
>table is non-representative):
>
>r.univar gpw

total null and non-null cells: 5246208
total null cells: 0

Of the non-null cells:
----------------------
n: 5246208
minimum: 0
maximum: 5.85072e-39
range: 5.85072e-39
mean: 5.68089e-44
standard deviation: 2.93343e-42
variance: 8.60502e-84
variation coefficient: 5163.69 %
sum: 2.98031e-37

>If everything is still zero, please let us know.

It is not exactly zero but very, very small.
Is there something wrong with this data? How can I check this?

Just for Information: I used GRASS 6.1 CVS.

Karl

--------------------------------------------------------------------------
Dr.-Ing. Karl BROICH Tel: +49 / (0) 89 / 6004 2478
Universität der Bundeswehr München Fax: +49 / (0) 89 / 6004 3858
Institut für Wasserwesen
Werner-Heisenberg-Weg 39
D 85577 Neubiberg
--------------------------------------------------------------------------

--
Markus Neteler <neteler itc it> http://mpa.itc.it
ITC-irst - Centro per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
Via Sommarive, 18 - 38050 Povo (Trento), Italy

4

Karl,

final hint :slight_smile:

You may define a custom color table with the rules option
of r.colors (see manual page).

CIESIN's color table for their data can be seen here:
http://sedac.ciesin.columbia.edu/plue/gpw/index.html?main.html&2
and
http://sedac.ciesin.columbia.edu/gpw/global.jsp

Cheers

Markus

On Wed, Dec 28, 2005 at 06:16:40PM +0100, Markus Neteler wrote:

Karl,

[ after having received offlist the data]
ok.

the problem is that GRASS by default applies
a linear color table. However, with the megacities
in Asia and elsewhere, this doesn't quite work

the solution is to apply a custom color table,
or, as a first approach, a logarithmic table

r.colors asds00gialpha1 col=grey.log
d.rast asds00gialpha1

Works :slight_smile:

Markus

On Wed, Dec 28, 2005 at 03:42:42PM +0100, Karl Broich wrote:
> Markus,
>
> At 11:23 28.12.2005 +0100, you wrote:
> >Karl,
> >
> >did you zoom to the map?
>
> no.
>
> >g.region rast=gpw -p
> >
> >Then you may check the statistics (probably just the color
> >table is non-representative):
> >
> >r.univar gpw
>
> total null and non-null cells: 5246208
> total null cells: 0
>
> Of the non-null cells:
> ----------------------
> n: 5246208
> minimum: 0
> maximum: 5.85072e-39
> range: 5.85072e-39
> mean: 5.68089e-44
> standard deviation: 2.93343e-42
> variance: 8.60502e-84
> variation coefficient: 5163.69 %
> sum: 2.98031e-37
>
>
> >If everything is still zero, please let us know.
>
> It is not exactly zero but very, very small.
> Is there something wrong with this data? How can I check this?
>
> Just for Information: I used GRASS 6.1 CVS.
>
> Karl
>
>
>
>
> --------------------------------------------------------------------------
> Dr.-Ing. Karl BROICH Tel: +49 / (0) 89 / 6004 2478
> Universität der Bundeswehr München Fax: +49 / (0) 89 / 6004 3858
> Institut für Wasserwesen
> Werner-Heisenberg-Weg 39
> D 85577 Neubiberg
> --------------------------------------------------------------------------
>

--
Markus Neteler <neteler itc it> http://mpa.itc.it
ITC-irst - Centro per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
Via Sommarive, 18 - 38050 Povo (Trento), Italy

--
Markus Neteler <neteler itc it> http://mpa.itc.it
ITC-irst - Centro per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
Via Sommarive, 18 - 38050 Povo (Trento), Italy