[OSRS-PROJ] Lambert Conformal Conic 1SP
Gerald I. Evenden
gerald.evenden at verizon.net
Mon Feb 10 10:42:57 EST 2003
Correct me if I am wrong but the definition of the Costa Rica
Norte projection is (in proj terms):
<costa-n> # Costa Rica Norte
proj=lcc ellps=clrk66 lat_1=10d28N lon_0=84d20W
x_0=500000 y_0=217820.522 k_0=0.99995696
no_defs <>
This shows tangential specification with scale factor.
What you seem to be confusing is that a non-unity scale factor
does, in essence, turn a tangential spec into a secant form but
I find that specious when the other basic elements of the
projection ONLY specify the base of tangency.
As and aside, what if the user specifies a scale factor
greater than one? Then we have neither tangency nor secancy. ;-)
In my book: LLC with one parallel: tangent form, LLC with two
parallels secant form.
A minor point, a LLC with two parallels can be turned into the
tangent equivalence with a appropriate scale factor greater than
unity. This is why it is nonsense to use the terms tangency/
secancy in any other sense other than whether one or two latitudes
are specified. The cartographer doesn't give a damn as he will
adjust the scale factor or double parallels to give the best fit
to his zone of interest.
Any, we are just squabbling over semantics.
On Sun, 2003-02-09 at 22:13, Clifford J Mugnier wrote:
>
> Costa Rica Zona Norte is defined as:
>
> Latitude of Origin: 10º 28'N
> Scale Factor at Origin: 0.99995696
>
> and
>
> Costa Rica Zona Sud is defined as:
>
> Latitude of Origin: 9º 00
> Scale Factor at Origin: 0.99995696
>
> Both are secant Lambert Conical Orthomorphic projections.
>
> Costa Rica is NOT tangential, it is secant as are ALL other Lambert
> Conformal Conics established by Army Map Service's Inter American Geodetic
> Survey in the 1950's.
>
> If it's tangential, then Scale Factor at Origin is equal to UNITY. Still
> PERIOD. Notice above parameters have Scale Factors at Origin less than
> unity. Still PERIOD.
>
...
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