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This fixes the current forward implementation of Peirce Quincuncial proj to correctly flip/reflect out the southern hemisphere to four triangles, and rotate entire result to a square or diamond. (It there resolves the issues identified with pull request https://github.com/OSGeo/PROJ/pull/2230 , where southern hemisphere was wrongly projected over northern, and reverses the restriction to northern hemisphere introduced there). It also adds additional lateral projection of the hemispheres.
- This PR adds an optional parameter `+type` which allows selection of projection. The `+type=square` and `+type=diamond` types match in principle ESRI's twin implementations of square and diamond PQ projs. The **default** if not specified is `+type=diamond`.
- The previous behaviour restricted to the northern hemisphere can be reproduced using the `+type=nhemisphere`, though this is an edge case only.
- An additional `+type=horizontal` and `+type=vertical` rectangular lateral versions have been added that place each hemisphere side-by-side. This is primarily to allow creation of projections such as Greiger Triptychial, which also require the additional optional params `scrollx` or `scrolly` in order to shift parts of the projection from one side of the map to the other.
- Additional documentation has been added to proj description, including quoting the usual meridian used in common usage of projection, and images showing the different types.
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* Document the default poder_engsager algorithm for tmerc.
* Give exact expression for phi' in terms of phi
* Aadd another datapoint on range of applicability + explanation for
complex numbers.
* Update tmerc figure with one reflecting poder/engsager algo.
Courtesy of @hobu.
Co-authored-by: Charles Karney <charles.karney@sri.com>
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Limit peirce_q to northern hemisphere, and fix images for adams_hemi, guyou and peirce_q
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- Central lon for zone 2 should be -d10, not d10
- Extra lobe was missing for zone 11
- New figure generated
- New test suite values generated
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- The current implementation of the Interrupted Goode Homolosine
projection emphasizes land area. This is a compliment projection
that emphasizes ocean area.
- A value of lon0=-160 produces a reasonable real-world map.
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regenerate associated images
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This commit adds five new projections to PROJ:
adams_hemi: Adams Hemisphere in a Square
adams_wsI: Adams World in a Square I
adams_wsII: Adams World in a Square II
guyou: Guyou
peirce_q: Pierce Quincuncial
The code originates from Gerry Evendens libproject and has been adapted
to work with modern PROJ. To ensure that the modified code works as
intended extensive test data has been created using libproject and
sproj so that no errors occured when porting from libproject to PROJ.
The test data is wrapped in a gie files. All test cases reproduce
results from libproject at the mm level.
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* Make tmerc an alias for etmerc
This switches the algorithm used in tmerc to the Poder/Engsager
tmerc algorithm. The original tmerc algorithm of Evenden/Snyder
origin can still be accessed by adding the +approx flag when
initializing a tmerc projection. The +approx flag can also
be used when initializing UTM projections, in which case the
Evenden/Snyder algorithm is used as well.
If a tmerc projection is instantiated on a spherical earth
the Evenden/Snyder algorithm is used as well since the
Poder/Engsager algorithm is only defined on the ellipsoid.
+proj=etmerc can still be instantiated for backwards compatibility
reasons.
Co-authored-by: Kristian Evers <kristianevers@gmail.com>
Co-authored-by: Even Rouault <even.rouault@spatialys.com>
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image to caption
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Implement the Equal Earth projection (closes #1085)
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