r.proj's "use different location" error while working in different dbases

[Nikos Alexandris]

GRASS-ers,

I have "wgs84" locations in different dbases, for example:
"/grassdb/ellas/wgs84" and "/grassdb/global/wgs84".

I want to "r.proj" something from "ellas" to "global" dbase and I get
the following error:

---
# working in "global"
g.gisenv

GISDBASE=/geo/grassdb/global
LOCATION_NAME=wgs84
MAPSET=PERMANENT

# trying to "pull" data
r.proj aster_gdem out=aster_gdem_ellas location=wgs84 mapset=PERMANENT
dbase=/geo/grassdb/ellas

ERROR: You have to use a different location for input than the current
---

This is a bug, ins't it? I suppose the "dbase=" parameter is not checked
at all in this case (?).

Best regards, Nikos

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[hamish-2]

Nikos Alexandris wrote:

> I have "wgs84" locations in different dbases, for example:
> "/grassdb/ellas/wgs84" and "/grassdb/global/wgs84".
>
> I want to "r.proj" something from "ellas" to "global" dbase
> and I get
> the following error:
>
> ---
> # working in "global"
> g.gisenv
>
> GISDBASE=/geo/grassdb/global
> LOCATION_NAME=wgs84
> MAPSET=PERMANENT
>
> # trying to "pull" data
> r.proj aster_gdem out=aster_gdem_ellas location=wgs84
> mapset=PERMANENT
> dbase=/geo/grassdb/ellas
>
> ERROR: You have to use a different location for input than
> the current
> ---
>
> This is a bug, ins't it? I suppose the "dbase=" parameter
> is not checked at all in this case (?).

yes, it appears so.


r.proj(.seg) has the following check:
    if (strcmp(inlocation->answer, G_location()) == 0)
        G_fatal_error(_("You have to use a different location for input than the current"));


maybe it should assemble indbase->answer/inlocation->answer
and test that against G_location_path(). ?  then dirsep hell?


please file a bug


Hamish



     

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[Nikos Alexandris]

Nikos:
> > I have "wgs84" locations in different dbases, for example:
> > "/grassdb/ellas/wgs84" and "/grassdb/global/wgs84".

> > I want to "r.proj" something from "ellas" to "global" dbase
> > and I get the following error:
> > ERROR: You have to use a different location for input than
> > the current

> > This is a bug, ins't it? I suppose the "dbase=" parameter
> > is not checked at all in this case (?).


Hamish:
> yes, it appears so.

> r.proj(.seg) has the following check:
>     if (strcmp(inlocation->answer, G_location()) == 0)
>         G_fatal_error(_("You have to use a different location for input than the current"));

> maybe it should assemble indbase->answer/inlocation->answer
> and test that against G_location_path(). ?  then dirsep hell?

> please file a bug


Done: http://trac.osgeo.org/grass/ticket/675

Alternative solution with respect to the specific example here: allow
g.copy to copy data from another dbase/location to the current dbase in
a location with identical name and projection definition of course (?).

Nikos

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[Glynn Clements]

Nikos Alexandris wrote:

> Alternative solution with respect to the specific example here: allow
> g.copy to copy data from another dbase/location to the current dbase in
> a location with identical name and projection definition of course (?).

We don't currently have any way to check whether two projections are
identical, and this isn't a trivial question. E.g.:

1. Some of the parameters are floating-point values, so we would need
to choose some kind of tolerance.

2. Are WGS84 and NAD83 the same? In the absence of grid shift files,
the only difference is that the eccentricity of the WGS84 and GRS80
ellipsoids differ by 1.5e-6.

3. If the projections use grid shift files, do we just check that they
use the same file, or do we compare their contents?

--
Glynn Clements <[hidden email]>
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[Nikos Alexandris]

Nikos Alexandris wrote:

> > Alternative solution with respect to the specific example here: allow
> > g.copy to copy data from another dbase/location to the current dbase in
> > a location with identical name and projection definition of course (?).


Glynn Clements:

> We don't currently have any way to check whether two projections are
> identical, and this isn't a trivial question. E.g.:
>
> 1. Some of the parameters are floating-point values, so we would need
> to choose some kind of tolerance.
>
> 2. Are WGS84 and NAD83 the same? In the absence of grid shift files,
> the only difference is that the eccentricity of the WGS84 and GRS80
> ellipsoids differ by 1.5e-6.
>
> 3. If the projections use grid shift files, do we just check that they
> use the same file, or do we compare their contents?

Seems not that easy after all. As a simple user I would expect that (at
least?) locations created using 'epsg:4326' would be easy to
compare/identify.

Nikos

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[hamish-2]

Nikos wrote:
> Seems not that easy after all. As a simple user I would
> expect that (at least?) locations created using 'epsg:4326'
> would be easy to compare/identify.

see the qgis bug tracker for real-life examples of why it is not.


Hamish



     

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[Timmie]

> We don't currently have any way to check whether two projections are
> identical, and this isn't a trivial question. E.g.:
Interesting.
Why does it say
"data set and location projection appear to match"
when importing a file into GRASS?

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