[GRASS-user] problem with reprojection of Hydro1k data

GRASS GRASS user
1

Hello,
First i'd like to know if anybody already used the Hydro1k data from USGS?
I try to make global maps of parameters from continental ones.
The initial projection is lambert azimutal equal area, with different latitude and longitude of origins for different continents. I defined one location by continent; then i reprojected all maps in a latlon global location, with WGS84 datum.
There are gaps between continents, for example between Asia and Europe and between Europe and Africa.
I wonder if the problem comes:
- from the data which don't perfectly cover the earth
- from my reprojection in grass
Thank you if somebody can help me
Regards
Stéphanie

2

Stéphanie,

On Fri, Feb 13, 2009 at 2:18 PM, FAROUX STEPHANIE
<stephanie.faroux@meteo.fr> wrote:

Hello,
First i'd like to know if anybody already used the Hydro1k data from USGS?
I try to make global maps of parameters from continental ones.
The initial projection is lambert azimutal equal area, with different
latitude and longitude of origins for different continents. I defined one
location by continent; then i reprojected all maps in a latlon global
location, with WGS84 datum.
There are gaps between continents, for example between Asia and Europe and
between Europe and Africa.
I wonder if the problem comes:
- from the data which don't perfectly cover the earth

... could be possible, I didn't try with Hydro1k data from USGS.

- from my reprojection in grass

How did you do that? Say, did you use the v.in.region trick
mentioned in the r.proj manual page which helps a lot?

Markus

3

Thank you for your answer Markus.
I didn't read the note in the r.proj page. I will try again and then we will see.
Stéphanie

Markus Neteler wrote:

Stéphanie,

On Fri, Feb 13, 2009 at 2:18 PM, FAROUX STEPHANIE
<stephanie.faroux@meteo.fr> wrote:
  

Hello,
First i'd like to know if anybody already used the Hydro1k data from USGS?
I try to make global maps of parameters from continental ones.
The initial projection is lambert azimutal equal area, with different
latitude and longitude of origins for different continents. I defined one
location by continent; then i reprojected all maps in a latlon global
location, with WGS84 datum.
There are gaps between continents, for example between Asia and Europe and
between Europe and Africa.
I wonder if the problem comes:
- from the data which don't perfectly cover the earth
    
... could be possible, I didn't try with Hydro1k data from USGS.

- from my reprojection in grass
    
How did you do that? Say, did you use the v.in.region trick
mentioned in the r.proj manual page which helps a lot?

Markus

4

I did it; results are not exactly the same but it's not enough because gaps between continents are still more important.

FAROUX STEPHANIE wrote:

Thank you for your answer Markus.
I didn't read the note in the r.proj page. I will try again and then we will see.
Stéphanie

Markus Neteler wrote:

Stéphanie,

On Fri, Feb 13, 2009 at 2:18 PM, FAROUX STEPHANIE
<stephanie.faroux@meteo.fr> wrote:

Hello,
First i'd like to know if anybody already used the Hydro1k data from USGS?
I try to make global maps of parameters from continental ones.
The initial projection is lambert azimutal equal area, with different
latitude and longitude of origins for different continents. I defined one
location by continent; then i reprojected all maps in a latlon global
location, with WGS84 datum.
There are gaps between continents, for example between Asia and Europe and
between Europe and Africa.
I wonder if the problem comes:
- from the data which don't perfectly cover the earth
    
... could be possible, I didn't try with Hydro1k data from USGS.

- from my reprojection in grass
    
How did you do that? Say, did you use the v.in.region trick
mentioned in the r.proj manual page which helps a lot?

Markus

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5

I try the v.in.region + v.proj + g.region + r.proj process (explained in the r.proj page) with a region whose reprojection doesn't allow to get a closed boarder: the projection of the raster doesn't work. Is it normal?
Thank you

FAROUX STEPHANIE wrote:

I did it; results are not exactly the same but it's not enough because gaps between continents are still more important.

FAROUX STEPHANIE wrote:

Thank you for your answer Markus.
I didn't read the note in the r.proj page. I will try again and then we will see.
Stéphanie

Markus Neteler wrote:

Stéphanie,

On Fri, Feb 13, 2009 at 2:18 PM, FAROUX STEPHANIE
<stephanie.faroux@meteo.fr> wrote:

Hello,
First i'd like to know if anybody already used the Hydro1k data from USGS?
I try to make global maps of parameters from continental ones.
The initial projection is lambert azimutal equal area, with different
latitude and longitude of origins for different continents. I defined one
location by continent; then i reprojected all maps in a latlon global
location, with WGS84 datum.
There are gaps between continents, for example between Asia and Europe and
between Europe and Africa.
I wonder if the problem comes:
- from the data which don't perfectly cover the earth
    
... could be possible, I didn't try with Hydro1k data from USGS.

- from my reprojection in grass
    
How did you do that? Say, did you use the v.in.region trick
mentioned in the r.proj manual page which helps a lot?

Markus

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

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