Changeset 8cfb486 in sasmodels for doc/guide/orientation
- Timestamp:
- Dec 20, 2017 4:16:27 PM (7 years ago)
- Branches:
- master, core_shell_microgels, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests
- Children:
- 5fb0634
- Parents:
- 06ee63c
- File:
-
- 1 edited
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doc/guide/orientation/orientation.rst
r06ee63c r8cfb486 128 128 symmetry. 129 129 130 There are alternative projections. The 131 `sinusoidal projection <https://en.wikipedia.org/wiki/Sinusoidal_projection>`_130 Alternative projections were considered. 131 The `sinusoidal projection <https://en.wikipedia.org/wiki/Sinusoidal_projection>`_ 132 132 works by scaling $\Delta\phi$ as $\Delta\theta$ increases, and dropping those 133 133 points outside $[-180, 180]$. The distortions are a little less for middle 134 134 ranges of $\Delta\theta$, but they are still severe for large $\Delta\theta$ 135 and the model is much harder to explain. The 136 `Guyou projection <https://en.wikipedia.org/wiki/Guyou_hemisphere-in-a-square_projection>`_ 135 and the model is much harder to explain. 136 The `azimuthal equidistance projection <https://en.wikipedia.org/wiki/Azimuthal_equidistant_projection>`_ 137 also improves on the equirectangular projection by extending the range of 138 reasonable values for the $\Delta\theta$ range, with $\Delta\phi$ forming a 139 wedge that cuts to the opposite side of the sphere rather than cutting to the 140 pole. This projection has the nice property that distance from the center are 141 preserved, and that $\Delta\theta$ and $\Delta\phi$ act the same. 142 The `azimuthal equal area projection <https://en.wikipedia.org/wiki/Lambert_azimuthal_equal-area_projection>`_ 143 is like the azimuthal equidistance projection, but it preserves area instead 144 of distance. It also has the same behaviour for $\Delta\theta$ and $\Delta\phi$. 145 The `Guyou projection <https://en.wikipedia.org/wiki/Guyou_hemisphere-in-a-square_projection>`_ 137 146 has an excellent balance with reasonable distortion in both $\Delta\theta$ 138 147 and $\Delta\phi$, as well as preserving small patches. However, it is 139 considerably more expensive to implement, and we have not yet computedthe148 considerably more overhead, and we have not yet derived the formula for the 140 149 distortion correction, measuring the degree of stretch at the point 141 $(\Delta\theta, \Delta\phi)$ in the correction.150 $(\Delta\theta, \Delta\phi)$ on the map. 142 151 143 152 .. note::
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