[Proj] SP1 question
Gerald I. Evenden
geraldi.evenden at gmail.com
Wed Nov 22 15:59:43 EST 2006
I am resending this because the proj list failed as I had not updated by email
address on the list. Also, I wanted to add a point about the scaling at the
end of the note.
On Wednesday 22 November 2006 1:34 pm, Gerald I. Evenden wrote:
> On Wednesday 22 November 2006 12:32 pm, Jamon Van Den Hoek wrote:
> > hi all,
> >
> > i'm having trouble achieving a transformation from a point's lat/long
> > coords into a user-defined projection with one standard parallel.
> >
> > i'm using PROJ.4's 1SP LCC function (at
> > http://www.remotesensing.org/geotiff/proj_list/lambert_conic_conformal_1s
> >p. html) with the following projection parameters:
> >
> > 1. Origin Longitude (£fo): 90¢X00¡¦00.000000¡¨
> > 2. Origin Latitude (£Xo): 43¢X22¡¦00.000000¡¨
> > 3. False Easting (Eo): 147218.6942 meters (482999.999 U.S. survey feet)
> > 4. False Northing (No): 0.0037 meters (0.012 U.S. survey feet)
> > 5. Scale Factor on Central Meridian (ko): 1.0000365285
> >
> > and the following code:
> >
> > C:\>proj.exe -I +proj=lcc +lat_1=43d22'0"N +lon_0=90d00'0"W
> > +k_0=1.0000365285 +x_0=147218.6942 +y_0=0.0037 +ellps=GRS80 44d10'00"N
> > 89d48'00"W (lat/long of point i
> > want to transform) 131d4'1.401"E 89d59'59.907"S'00"N 89d48'00"W
> > (not sure how to interpret this output line)
> >
> > 1d48'57.388"W 43d21'8.09"N (if "enter" is
> > pressed again, this it outputted)
>
> The main thing wrong is that you seem to want a forward projection yet set
> the -I option to compute the inverse projection. This explains why you get
> geographic coordinates as output.
>
> I constructed the following script:
>
> lproj +proj=lcc +lat_1=43d22n +lon_0=90dw +k_0=1.0000365285 \
> +x_0=147218.6942 +y_0=0.0037 +ellps=GRS80 <<EOF
> 89d48'00"W 44d10'00"N
> EOF
>
> and got the following answer:
>
> 163217.09 88911.46
>
> Also note that longitude precedes the latitude on input.
>
> Another note: it is unusual to use a k_0 factor greater than 1. A more
> typical value would be 0.999 and the value depends of the latitude range of
> your projected area.
The above is my added point.
--
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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