[GRASSLIST:3890] Re: Projection and m.in.e00

[Michel Wurtz]

Ben Logan wrote:
[...]
> Now I'll import the e00 file (boundary.e00) into a new mapset to avoid
> the problems mentioned in the m.in.e00 manpage (the 'saa' mapset
> doesn't exist yet):
> 
> GRASS:~/grass5.0/saa > m.in.e00 input=boundary.e00 mapset=saa verbose=1 logfile=out.log

m.in.e00 doesn't (yet) interpret the projection info, except
for scale value.  I plan to write a translator for projection
info from e00 to Grass, so m.in.e00 could at least build a
correct header for the file, and if possible have an option to
reproject the data in the map projection but it is not easy to
have a full list of the projections used by e00 and how they
are defined by Grass (not complicated, but long if you want them
all).  m.in.e00 actually set allways proj to 99 and zone to 0.

However, if you use verbose=4 (at least), the logfile will show
you the content of the projection info of the e00 file imported.
You can then modify (by hand) the grass header and the mapset
projection, and use v.proj to reproject your data...

When using :

grass> m.in.e00 boundary.e00 verbose=4 logfile=boundary.log

the log file contains :

...
SIN  2
Ignoring data
LOG  2
Ignoring data
PRJ  2
Current Mapset : Ignoring projection data
Projection    ALBERS
Datum         NAD83
Zunits        NO
Units         METERS
Spheroid      GRS1980
Xshift        0.0000000000
Yshift        0.0000000000
Parameters
 34  0  0.000 /* 1st standard parallel
 38  0  0.000 /* 2nd standard parallel
-82  0  0.000 /* central meridian
 33  0  0.000 /* latitude of projection's origin
0.00000 /* false easting (meters)
0.00000 /* false northing (meters)
EOP
Scale used = 1.000000
IFO  2
BOUNDARY.BND XX 4 16 1
INFO table .BND
xmin = -420133.160000, ymin = 16980.227000
xmax = 353657.000000, ymax = 730721.940000
Creating region
...

> Now I'll quit Grass and restart in the new 'saa' mapset (I guess it
> isn't strictly necessary to exit Grass, but ...).
> 
>  From the new mapset, I 'cd $LOCATION'.  Here's what the WIND file
> looks like:
> 
> proj:       99
> zone:       0
> north:      730721.94
> south:      16980.227
> east:       353657
> west:       -420133.16
> cols:       21666124
> rows:       19984768
> e-w resol:  0.03571429
> n-s resol:  0.03571429
> 
> Well, clearly this is all wrong if in fact the source e00 was in
> lat/lon projection.

Since the original file is not in lat/long coordinates, it is not
wrong (in fact east, west, north and south values are calculated from
the data.  The logfile show the content of the .bnd file, wich are
the same).

Use v.proj to have a lat/long map...

--
Michel WURTZ - DIG - Maison de la télédétection
               500, rue J.F. Breton
               34093 MONTPELLIER Cedex 5