[Proj] a problem about polyconic inverse translation

[Gerald Evenden]

American Polyconic will not inverse project when longitudes are more
than 90 from the central meridian.

Polyconic was normally used for large scale mapping where the longitude
extent was typically less than a degree.  I do not believe it is 
currently in
common use as it is neither conformal nor equal area.

On Nov 2, 2004, at 9:25 PM, ~{UEA"~} wrote:

> Hi,
>    I am doing some work on polyconic inverse translation using proj4.
>    and I find  a minor  problem. What I have done is:
>
> $proj +proj=poly +lon_0=0 <<EOF
>> 70e 3dN
>> EOF
> 7776455.16  580425.56
>
> $invproj +proj=poly +lon_0=0 <<EOF
>> 7776455.16  580425.56
>> EOF
> 70dE 3dN
>
> All is ok,but when I do the followed:
>
> $proj +proj=poly +lon_0=0 <<EOF
>> 160e 3dN
>> EOF
> 17723619.31  1629185.73
>
> $invproj +proj=poly +lon_0=0 <<EOF
>> 17723619.31  1629185.73
>> EOF
> *   *
> I got nothing .
>
> I also tried some other data , if the latitude is small and longitude 
> is large ,I can't get correct result  or got not noting.
>
> I look at the source file PJ_poly.c, and find that the inverse 
> translation is a kind of iteraor.
>
> Is it possible that there is a minor bug in the polyconic inverse 
> translation algorithm ?
>
> 	
> ---------------------------------------------------------
> 	Zhang Lili
> 	Institute of Geography and Nature Resource Reseach,
> 	Chinese Academy of Sciences
> ---------------------------------------------------------
>     Building 917, Chaoyang District, Beijing, 100101, China
>     E-Mail: zhangli at supermap.com
>     Http://www.igsnrr.ac.cn, www.gischina.com
>     Voice: +86-10-82736655   Fax: +86-10-82734630
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> ~{!!!!!!!!!!!!!!!!!!!!~}2004-11-03
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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
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