[GRASS5] PROJ_INFO and prime meridian

[Markus Neteler]

(cc grass5)

On Wed, Jun 04, 2003 at 08:54:45PM +0100, Paul Kelly wrote:
> 
> 
> On Wed, 4 Jun 2003, Markus Neteler wrote:
> 
> > > > lat_0: 45.9000000000   <- given 45:54N
> > >
> > > > lat_1: 33.0000000000   <- calculated by GRASS, given 'return'
> > > > lat_2: 45.0000000000   <- calculated by GRASS, given 'return'
> > >
> ...
> > Deleting
> >  lat_1: 33.0000000000
> >  lat_2: 45.0000000000
> >
> > g.region -l
> > Unable to initialise PROJ.4 with the following parameter list:
> >  proj=lcc lat_0=45.9000000000 lon_0=14.0000000000 x_0=800000.0000000000
> > y_0=601000.0000000000 a=6377397.155000 rf=299.152813
> > towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68
> > The error message was 'conic lat_1 = -lat_2'
> > ERROR: Can't get projection key values of current location
> >
> 
> Mmmm obvious suggestion then:
> delete lat_0 and lat_2 from PROJ_INFO; add
> lat_1: 45.9
> 
> Is this any better?

Yes. Now the shift is reduces to 70m eastwards and 170m northwards.

The reference Orthophoto I have verified with a vector street map from
a different data provider, they match.

I have made a screenshot of a zoomed area:
http://mpa.itc.it/markus/tmp/lcc_1945_ortho2000.png
(1MB)
http://mpa.itc.it/markus/tmp/lcc_1945_ortho2000_small.png 
(500kb)

So maybe now only the rome40 datum for the LCC location 
is wrong (and the prime meridian slightly different).

> Also the first time you tried it (the original PROJ_INFO) what did r.proj
> print out as the parameters being used? Did it have lat_1 or lat_0 and
> lat_2?

Reverting the PROJ_INFO to the original version, it prints:
r.proj in=268_09ne.rect out=test loc=bzLCC map=PERMANENT

Input Projection Parameters: +proj=lcc +lat_0=45.9000000000
+lat_1=33.0000000000 +lat_2=45.0000000000 +lon_0=14.0000000000
+x_0=800000.0000000000 +y_0=601000.0000000000 +a=6377397.155000
+rf=299.152813 +towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68

Output Projection Parameters: +proj=tmerc +lat_0=0.0000000000 +lon_0=9.0
+k_0=0.9996000000 +x_0=500000.0 +y_0=-5000000.0 +a=6378388.000000
+rf=297.000000 +towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68

Markus