diff options
| author | Even Rouault <even.rouault@spatialys.com> | 2019-11-29 21:16:27 +0100 |
|---|---|---|
| committer | Even Rouault <even.rouault@spatialys.com> | 2019-11-29 21:16:27 +0100 |
| commit | 5f749c70c7893f867801d458bdf51abbbaad4f64 (patch) | |
| tree | 438f52d719d5ab6665d158dba0395ac7180228bb /docs/source/operations/operations_computation.rst | |
| parent | c5d8c0862f3a368abfd10ca81676baaa0df8ea91 (diff) | |
| download | PROJ-5f749c70c7893f867801d458bdf51abbbaad4f64.tar.gz PROJ-5f749c70c7893f867801d458bdf51abbbaad4f64.zip | |
operations_computation.rst: fixes
Diffstat (limited to 'docs/source/operations/operations_computation.rst')
| -rw-r--r-- | docs/source/operations/operations_computation.rst | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/docs/source/operations/operations_computation.rst b/docs/source/operations/operations_computation.rst index 85cbfa09..33c635b2 100644 --- a/docs/source/operations/operations_computation.rst +++ b/docs/source/operations/operations_computation.rst @@ -71,7 +71,7 @@ With the above example of two geographic CRS, that have an identified identifier the algorithm will first search in the coordinate operation related tables of the ``proj.db`` if there are records that list direct transformations between the source and the target CRS. The -transformations typically involve :ref:`Helmert <helmert>-style operations or datum shift based on +transformations typically involve :ref:`Helmert <helmert>`-style operations or datum shift based on grids (more esoteric operations are possible). A request similar to the following will be emitted: @@ -405,10 +405,9 @@ Actually, WGS 84 has been considered during the above lookup, because there are transformations between AGD84 and WGS 84 and WGS 84 and GDA2020. However those have been discarded in a step which we did not mention previously: just after the initial filtering of results and their sorting, there is a final filtering -that is done. In the list of sorted results, if a less prioritary result than -its previous one has the same area of use, but a lesser accuracy and that the -more accurace results does not use grids, or the grids are available, then the -less accurate result is discarded. +that is done. In the list of sorted results, given two operations A and B that +have the same area of use, if B has an accuracy lower than A, and A does not use +grids, or all the needed grids are available, then B is discarded. If one forces the datum hub to be considered to be EPSG:4326, ones gets: @@ -593,7 +592,7 @@ the transformation from a compound CRS made of a geographic CRS to another geogr It first starts by the vertical transformations from the vertical CRS of the source compound CRS to the target geographic CRS, using the strategy detailed -in verttogeog_ +in :ref:`Vertical CRS to a Geographic CRS <verttogeog>` What we did not mention is that when there is not a transformation registered between the vertical CRS and the target geographic CRS, PROJ attempts to find |