[Proj] GeoTiff <-> Proj.4

Gerald I. Evenden geraldi.evenden at gmail.com
Fri Oct 3 14:26:37 EDT 2008

On Friday 03 October 2008 11:25:47 am support.mn at elisanet.fi wrote:
> Hello,
> I am still asking if it is totally not possible to use omerc to decode
> GeoTiff projections 3,4 and 5. The problem seems to be wha to do with the
> http://en.wikipedia.org/wiki/American_National_Standards_Institute

I first thought was: "what a good idea," but skimming on to ISO reference the 
criticism section brought up the cost involved and that reminded me of a long 
ago experience.  I thought it would be a good idea to get a copy of the ANSI 
C standards but suddenly ran into the $$$  for a copy.

> More about Geotiff <-> Proj.4:
> Ref 1:
> http://www.remotesensing.org/geotiff/proj_list/lambert_conic_conformal_2sp.
> Ref 2:
> http://www.remotesensing.org/geotiff/spec/geotiff3.html#3.1.3.
> Ref 1 gives:
> +proj=lcc
>               +lat_1=Latitude of first standard parallel
>               +lat_2=Latitude of second standard parallel

They should really be called the secant parallels.  There is 
nothing "standard" about them.

The alternate lcc is to specify the parallel of tangency and then k_0 which 
does the same thing.

>               +lat_0=Latitude of false origin
>               +lon_0=Longitude of false origin

Oh, please! "of false origin" good grief.

>               +x_0=False Origin Easting
>               +y_0=False Origin Northing
> Ref 2 gives:
> +proj=lcc
>               +lat_1=Latitude of first standard parallel
>               +lat_2=Latitude of second standard parallel
>               +lat_0=Latitude of natural origin (ProjNatOriginLatGeoKey)
>               +lon_0=Longitude of projection center (ProjCenterLongGeoKey)
>               +x_0=False Origin Easting
>               +y_0=False Origin Northing

Terrible, terrible.  Proj may have also been guilty of the "standard" part.

> I am starting to belive that best way to deal with the problem is to first
> allocate lat_1, lat2, lat_ts and then start to look after any lat or lon
> and put them to lat_0 and lon_0. Since every creator of GeoTiff files puts
> them randomly somwhere what is left.

lat_ts is not involved with conics.

Is there an editor or editing group associated with these sites?

> Regards Janne.

The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist

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