[Proj] Implementation(s) for Oblique Stereographic

Gerald I. Evenden gerald.evenden at verizon.net
Thu Oct 27 14:51:47 EDT 2005

On Thursday 27 October 2005 06:38 am, Oscar van Vlijmen wrote:
> When sorting out the stereographic problems of some applications and
> databases, one might also want to look at the oldies:
> 2036: NAD_1983_CSRS98_New_Brunswick_Stereographic
> 2200: ATS_1977_New_Brunswick_Stereographic
> 2290: Prince_Edward_Island_Stereographic
> 2291: NAD_1983_CSRS98_Prince_Edward_Island

I have the publications from UNB and libproj4 +proj=sterea can be used with 
the above.  I have also have happy users from PEI with sterea.  I can only 
check with UNB values to the centimeter as their examples are only to 0.01 

> 22700: Deir_ez_Zor_Levant_Zone
> 22780: Deir_ez_Zor_Levant_Stereographic
> For the above mentioned e.g. the ESRI-ArcGIS projected coordinate systems
> list says "Double_Stereographic".

If the specs say Double Stereographic and with the usage of scale factor of 
1.0 (where +k_0=1) at the a point of tangency at the central meridian then 
sterea should do the job.  In theory, you could have Double Stereographic 
with other conditions.  Note: in usage +k_0 may not be 1.; it is just that if 
it is, then the scale should be 1.

> Dutch RD, Romanian Stereo 33 & 70, Polish quasi-stereographic have already
> been discussed.
> I believe Dutch RD can be approximated with sub-mm accuracy by sterea.
> Polish quasi-stereographic can only be approximated by sterea with sub-cm
> accuracy. Probably this projection will be in use until at least 2009.
> The sterea approximation for Romanian Stereo 70 is also not better than
> sub-cm level, but I have not enough test points to verify this.
> Collector's item:
> the "Alaska Conformal" projection is a unique modified oblique
> stereographic projection. See PJ23Z0 or alconfor/inv in GCTP2. The GCTP
> test suite has enough test points.

The Alaskan Modified Stereographic is a warped surface approximated by 
polynomial distortion.  Somewhat similar to the New Zealand grid.  The basic 
stereographic was used in its determination but thats where the similarity 

The GCTP test suite is manic with the number of points.
Jerry and the low riders:Daisy May and Joshua
"The being cannot be termed rational or virtuous,
who obeys any authority, but that of reason."
---Mary Wollstonecraft 1792

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