The Lambert azimuthal equal-area

[Morten Hulden]

Before anyone points it out, I want to correct my mistake:
I realize now LEAC and LAEA are two different projections, and the one
Seppo asked about was the azimuthal projection, not the conical. So here's
the prescription for including both LEAC and LAEA:
.....
diff -w table.h table.h.org

20,24c20
< #define LEAC 7
< #define LAEA 8
< 
< #define NPROJES 9
< 
---
> #define NPROJES 7

.....
diff -w table.c table.c.org

74,96d73
<  TABLE[LEAC][LAT0].ask = 1;
<  TABLE[LEAC][LAT0].def_exists = 1;
<  TABLE[LEAC][LAT0].deflt = 55.0;
< 
<  TABLE[LEAC][LON0].ask = 1;
<  TABLE[LEAC][LON0].def_exists = 1;
<  TABLE[LEAC][LON0].deflt = 20.0;
< 
<  TABLE[LEAC][LAT1].ask = 1;
<  TABLE[LEAC][LAT1].def_exists = 1;
<  TABLE[LEAC][LAT1].deflt = 0.0;
< 
<  TABLE[LEAC][SOUTH].ask = 1;
<  TABLE[LEAC][SOUTH].def_exists = 1;
< 
<  TABLE[LAEA][LAT0].ask = 1;
<  TABLE[LAEA][LAT0].def_exists = 1;
<  TABLE[LAEA][LAT0].deflt = 55.0;
< 
<  TABLE[LAEA][LON0].ask = 1;
<  TABLE[LAEA][LON0].def_exists = 1;
<  TABLE[LAEA][LON0].deflt = 20.0;
< 
121,122d97
<    if (G_strcasecmp(str,"LEAC",4) == 0)   return LEAC;
<    if (G_strcasecmp(str,"LAEA",4) == 0)   return LAEA;

.......
Recompile g.setproj and add to etc/projection:
leac:Lambert Equal Area Conic
laea:Lambert Azimuthal Equal Area


On Wed, 31 Mar 1999, Morten Hulden wrote:

> I tried the leac projection on data from the Eurasia Land Cover Data Base
> at usgs.gov. They don't tell what first standard parallel they used
> for their data so I tried to use the same value as the central parallel
> (55N). I then used r.proj to import elevation data (from DEM) into this
> mapset, and it fits nicely, but _not_ exaxtly. 

Of course not you stupid idiot, you used the wrong projection! And LAEA
does not have a first standard parallel parameter.

Well, after correcting the mistake I tried it again, and it fits to the
pixel! I also used v.proj to convert the borders and coastline-island-lake
(World Data Bank) from ll projection to LAEA and they too fit precisely.


sorry for the mess
Morten Hulden