[Proj] GeoTiff <-> Proj.4

[Gerald I. Evenden]

On Wednesday 01 October 2008 10:20:41 am support.mn at elisanet.fi wrote:
> I resend the list:
>
> ProjLinearUnitSizeGeoKey 3077 in meters
>
> Angulars:
>
> ProjStdParallelGeoKey 3078 in GeogAngularUnit -> lat_1
> ProjStdParallel2GeoKey 3079 in GeogAngularUnit -> lat_2
> ProjOriginLongGeoKey 3080 in GeogAngularUnit -> lon_0
> ProjOriginLatGeoKey 3081 in GeogAngularUnit -> lat_0
> ProjFalseOriginLongGeoKey 3084 in GeogAngularUnit -> ?
> ProjFalseOriginLatGeoKey 3085 in GeogAngularUnit -> ?
> ProjCenterLongGeoKey 3088 in GeogAngularUnit -> ?
> ProjCenterLatGeoKey 3089 in GeogAngularUnit -> ?
>
> Linears:
>
> ProjFalseEastingGeoKey 3082 in ProjLinearUnits -> x_0
> ProjFalseNorthingGeoKey 3083 in ProjLinearUnits -> y_0
> ProjFalseOriginEastingGeoKey 3086 in ProjLinearUnits -> ?
> ProjFalseOriginNorthingGeoKey 3087 in ProjLinearUnits -> ?
> ProjCenterEastingGeoKey 3090 in ProjLinearUnits -> ?
> ProjCenterNorthingGeoKey 3091 in ProjLinearUnits -> ?
>
> Ratios:
>
> ProjScaleAtOriginGeoKey 3092 in ratio -> k_0
> ProjScaleAtCenterGeoKey 3093 in ratio -> ?
>
> Others:
>
> ProjAzimuthAngleGeoKey 3094 in GeogAzimuthUnit -> alpha
> ProjStraightVertPoleLongGeoKey 3095 in GeogAngularUnit -> ?
> ProjRectifiedGridAngleGeoKey 3096 in GeogAngularUnit -> ?

?? I'm sorry, this is ridiculous.  Not the email but the above nomenclature.

Yes, I agree: "?"

A question: is the "Proj" part of the above list referring to the proj we all 
know and love?

As an aside, the problems of linear units in proj, proj4, libproj4 is probably 
forgotten so I will make a reminder: units are established by the unit that 
is used to define the Earth's radius, R=, or semi-major axis, a=.  If R=1 
then the units are an Earth with a radius=1 so an easting of 100,000 would be 
a ridiculous value.  If a is in US surveyor's feet then easting and northing 
must be in US surveyor's feet.  If one uses the internal ellipsoid figure 
table, ellps=, then because all a= entries in the table are in meters the 
user must refer to the other linear unit items in meters.

BTW: using lproj without specifying a radius or semi-major axis will cause a 
default R=1.

The bottom line is that the user is responsible for both defining the linear 
units as well as ensuring parameter unit consistency.

-- 
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