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Bug with the stereographic projection at equator #194

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proj4-bot opened this Issue May 22, 2015 · 0 comments

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proj4-bot commented May 22, 2015

Reported by thibbo on 22 Oct 2012 06:08 UTC
The stereographic projection multiplies the coordinates by 2 where lat_0 is set to 0.

The commands used are :

$ wgs='+title=long/lat:WGS84 +proj=longlat +ellps=WGS84 +datum=WGS84 +units=m'

$ echo "-75 35" | cs2cs -f "%.3f" $wgs +to +proj=stere +lat_0=0.00001 +lon_0=-96.0 +ellps=WGS84 +datum=WGS84 +units=m +x_0=0.0 +y_0=0.0 +k=0.9

For the same point :
lat_0=0.00001 gives 1912137.545 3711082.505
lat_0=0 gives 3824275.304 7422167.152

The bug is at line 44 of PJ_stere.c :
A = 2. * P->akm1 / (1. + cosX * coslam);
This line may be :
A = P->akm1 / (1. + cosX * coslam);

Sorry for my English, I am french.

Migrated-From: https://trac.osgeo.org/proj/ticket/194

kbevers added a commit that referenced this issue Oct 18, 2016

Fixed issue #194 (Bug with the stereographic projection at equator) t…
…hat multiplied equatorial coordinates by 2

@kbevers kbevers closed this Oct 18, 2016

@kbevers kbevers added this to the 4.10.0 milestone Oct 18, 2016

QuLogic added a commit to QuLogic/cartopy that referenced this issue Sep 27, 2018

TST: Update image for fixed Stereographic projection.
This is a known bug fix in proj.4 5.0.0, wherein lat_0=0 used to
erroneously multiply results by 2.

See OSGeo/proj.4#194

QuLogic added a commit to QuLogic/cartopy that referenced this issue Sep 27, 2018

TST: Update image for fixed Stereographic projection.
This is a known bug fix in proj.4 5.0.0, wherein lat_0=0 used to
erroneously multiply results by 2.

See OSGeo/proj.4#194

QuLogic added a commit to QuLogic/cartopy that referenced this issue Sep 27, 2018

TST: Update image for fixed Stereographic projection.
This is a known bug fix in proj.4 5.0.0, wherein lat_0=0 used to
erroneously multiply results by 2.

See OSGeo/proj.4#194

QuLogic added a commit to QuLogic/cartopy that referenced this issue Sep 27, 2018

TST: Update image for fixed Stereographic projection.
This is a known bug fix in proj.4 5.0.0, wherein lat_0=0 used to
erroneously multiply results by 2.

See OSGeo/proj.4#194

QuLogic added a commit to QuLogic/cartopy that referenced this issue Oct 3, 2018

TST: Update image for fixed Stereographic projection.
This is a known bug fix in proj.4 5.0.0, wherein lat_0=0 used to
erroneously multiply results by 2.

See OSGeo/proj.4#194
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