[Geotiff] Projection CS Encoding

[Brent Shaw]

Does anyone out there have any experience encoding geotiffs that are
referenced with a standard transformation method (e.g., Lambert
Conformal, Polar Stereographic, Mercator) on a user-defined projection?
For example, I can create an image where I know:
 
1.  Projection is Lambert Conformal 
2.  I know both standard parallels in degrees
3.  I know the standard longitude in degrees
4.  I know the spacing of the pixels along either of the standard
latitudes in meters
5.  I can compute the lat/lon of any raster pixel in the image to use as
a tie points.  Since I know items 1-4, I really should only need 1 tie
point, but I can compute any of the lat/lons with routines I already
have.  
 
What I specifically don't understand how to use for this case is the
ModelTiePointTag and the PixelScaleTag.  It seems as if the tie points
always need to be specified in some sort of distance unit, which I don't
know and cannot readily compute.  So, is there anyway to encode the
information such that the tie points are specified in lat/lon, but still
use a Projected CS with the other parameters specified?  
 
Thanks for any help anyone can provide.
 
Regards,
Brent
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