[Proj] setting lambert conformal conic projection in gdalwarp

[Mikael Rittri]

Hello Matt,

I think there are many GIS systems, apart from proj.4, 
that don't handle the case where the Lambert cone has
degenerated into a cylinder. So my guess is that there
is something wrong with your metadata.  

Possibly, the intention was to define a Lambert Conformal
Conic with one standard parallel at 50dN. If so, and if 
we assume WGS84, the Proj.4 definition would be

  +proj=lcc +lat_1=50 +lat_0=50 +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs

If this is the true coordinate system of your source image,
then "up" in the source image would be roughly northwest (in
UTM zone 18).  

On the other hand, if the metadata really are correct, 
it should be possible to emulate the coordinate system 
by using ordinary Mercator like this:

  +proj=merc +lon_0=0 +x_0=0 +y_0=-6413524.5942 +datum=WGS84 +units=m +no_defs

where the false northing y_0 is chosen so that 
0dE, 50dN will be projected to 0, 0. If this is correct, 
then "up" in the source image should be true north. 

Best regards,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

________________________________

From: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] On Behalf Of Mathew Fox
Sent: den 17 augusti 2011 15:16
To: proj at lists.maptools.org
Subject: [Proj] setting lambert conformal conic projection in gdalwarp


Hi Jose, Charles, 

thanks for your input.
Now, what is a reasonable solution for this? Can I use a custom projection in gdal (parsing the parameters without naming it "lcc")?

Matt.

> Matt

>
> There is a problem with the lcc projection. The two latitudes +lat_1 and
> +lat_2 define the standard parallels, where the cone intersects the
> ellipsoid. They can't be both zero (the cone would degenerate into a

> cylinder).

Of course, they *can* both be zero and the equations then become those
of the Mercator projection.  It's just that the authors of proj.4 chose
not to handle this case.

   --Charles


Hi all,

I am having problems with the Lambert Conformal Conic projection.

I am trying to convert an LCC file into UTM:

gdalwarp -of GTiff -s_srs '+proj=lcc +lat_1=0 +lat_2=0 +lat_0=50  +lon_0=0

+x_0=0 +y_0=0 +units=m +no_defs' -t_srs '+proj=UTM +zone=18 +units=m
+datum=NAD83 +no_defs' cols.asc cols.tif

I got the parameters from an existing LCC file.

Problem is, when I try to set this projection to my file I get an error

about the projection parameters.
ERROR 6: Failed to initialize PROJ.4 with `+proj=lcc +lat_1=0 +lat_2=0
+lat_0=50 +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs '.
conic lat_1 = -lat_2

Thank you in advance for any suggestions.


Matt.