[Proj] problem with Tangent plane stereographic proj

[Gerald Evenden]

ENU is an unknown quantity for me but I can at least comment on various 
aspects
of your numbers with the following shell script:

vals="+proj=stere +ellps=WGS84 +lat_0=45.65 +lon_0=4.55 +k=1"
cat <<EOF >data
45d48'05.3757 4d35'31.7851 296.944
45d48'05.3685 4d35'31.8064 297.014
45d48'05.3624 4d35'31.8254 296.924
EOF
echo "forward"
lproj -r $vals data >data2
cat data2
echo "recyle with binary pipe"
lproj -r $vals data -o | lproj $vals -I -i -W4 -s
echo "original data"
cat data
echo "recycle using formated intermediate data"
lproj $vals data2 -I -W4 -s

The results of this script are as follows:

forward
3277.74 16838.81 296.944
3278.20 16838.59 297.014
3278.61 16838.40 296.924
recyle with binary pipe
45d48'05.3757"N 4d35'31.7851"E
45d48'05.3685"N 4d35'31.8064"E
45d48'05.3624"N 4d35'31.8254"E
original data
45d48'05.3757 4d35'31.7851 296.944
45d48'05.3685 4d35'31.8064 297.014
45d48'05.3624 4d35'31.8254 296.924
recycle using formated intermediate data
45d48'05.3758"N 4d35'31.7850"E 296.944
45d48'05.3686"N 4d35'31.8063"E 297.014
45d48'05.3625"N 4d35'31.8252"E 296.924

These are values for (American) Oblique Stereographic from libproj4.

The only thing that I see as odd is the specification of "+ellps=wgs84" 
which
will normally cause failure because it should read "+ellps=WGS84".  This
applies to both my old proj4 distribution as well as libproj4.  Thus 
there
appears to be some add-on enhancement to "ENU".

Details as to what is in ENU would be required before I could make any
additional comments.

On May 2, 2005, at 9:44 AM, UW+R SA, J Vallet wrote:

> I am encountering problem with a projection (type tangent plane 
> stereographic) that does not give the same results if i run the 
> projection one time and then the reverse. the lat, long differs 
> significantly:
>
> my projection:
> lat/long (wgs84)
> 45d48'05.3757 4d35'31.7851 296.944
> 45d48'05.3685 4d35'31.8064 297.014
> 45d48'05.3624 4d35'31.8254 296.924
>
> -> ENU (+proj=stere +ellps=wgs84 +lat_0=45.65 +lon_0=4.55 +units=m 
> +k=1)
>
> 3277.74 16838.81    296.944
> 3278.20 16838.59    297.014
> 3278.61 16838.40    296.924
>
> ->Lat/Long with Inverse projection (-I)
>
> 45d40'45.433"N  4d45'58.076"E    296.944
> 45d40'45.448"N  4d45'58.066"E    297.014
> 45d40'45.461"N  4d45'58.058"E    296.924
>
> Theoritically, it must be the same as the fisrt set of coords...but not
>
> what am i doing wrong???
>
> thanks in advance for your help!
>
> Julien
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>
>
_____________________________________
Jerry and the low riders: Daisy Mae and Joshua.
"The whole religious complexion of the modern world is due to the
absence from Jerusalem of a lunatic asylum." Havelock Ellis, 1914