[Proj] Parsing Lambert Conformal Conic in GDAL
kyle at pobox.com
Fri Jan 3 11:54:16 EST 2014
On Fri, Jan 3, 2014 at 8:49 AM, Andre Joost <andre+joost at nurfuerspam.de> wrote:
> Am 03.01.2014 04:00, schrieb Kyle Shannon:
>> Is it okay to set a lat_1=lat_0,
>> and also specify lat_2. I suspect it is, but I haven't found any
>> concrete definition on limits (and I don't really think there are,
>> within reason).
>> Thought I'd consult the pros on the list to be sure.
> In the formulas given by Snyder, a single parallel LCC projection is
> defined by lat_1=lat_2, but he makes no special treatment for lat_0 (the
> latitude of origin) is equivalent to lat_1 or lat_2 or not.
Right, I feel that lat_0 shouldn't really be considered in this logic.
> Reading older proj trac tickets, I gathered that lat_0=lat_1 is
> misinterpreted in proj4 as lcc single parallel projection. This does not
> coincide with the WKT projection strings supplied by ESRI and others.
Correct. It may be a LCC 1SP, but it doesn't *have* to be. It
depends on the presence of lat_2.
> André Joost
> Proj mailing list
> Proj at lists.maptools.org
My interpretation is that lat_1 must always be specified. Whether or
not it is equal to lat_0 seems irrelevant. If lat_1 == lat_2, then it
is a LCC 1SP.
BTW, are you referring to 'Map Projections: A Working Manual' or
another Snyder publication.
More information about the Proj