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| author | Kristian Evers <kristianevers@gmail.com> | 2018-05-23 15:49:28 +0200 |
|---|---|---|
| committer | Kristian Evers <kristianevers@gmail.com> | 2018-05-24 08:42:18 +0200 |
| commit | 920978baa9ab974719c57a127a99ebf729370748 (patch) | |
| tree | 9403c87b12ccbe5fbe48b75b1f103db2f2671f1a /docs/source/usage | |
| parent | 37ebb8f9f0cc5083d22f84433fb2de0fdde8be00 (diff) | |
| download | PROJ-920978baa9ab974719c57a127a99ebf729370748.tar.gz PROJ-920978baa9ab974719c57a127a99ebf729370748.zip | |
Add doc section with description of behavioural changes between PROJ versions
Diffstat (limited to 'docs/source/usage')
| -rw-r--r-- | docs/source/usage/differences.rst | 47 | ||||
| -rw-r--r-- | docs/source/usage/index.rst | 2 |
2 files changed, 48 insertions, 1 deletions
diff --git a/docs/source/usage/differences.rst b/docs/source/usage/differences.rst new file mode 100644 index 00000000..58e92cd8 --- /dev/null +++ b/docs/source/usage/differences.rst @@ -0,0 +1,47 @@ +.. _differences: + +================================================================================ +Known differences between versions +================================================================================ + +Once in a while, a new version of PROJ causes changes in the existing behaviour. +In this section we track deliberate changes to PROJ that break from previous +behaviour. Most times that will be caused by a bug fix. Unfortunately, some bugs +have existed for so long that their faulty behaviour is relied upon by software +that uses PROJ. + +Behavioural changes caused by new bugs are not tracked here, as they should be +fixed in later versions of PROJ. + +Version 5.0.0 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + +Longitude wrapping when using custom central meridian +------------------------------------------------------------------------------- + +By default PROJ wraps output longitudes in the range -180 to 180. Previous to +PROJ 5, this was handled incorrectly when a custom central meridian was set with +:option:`+lon`. This caused a change in sign on the resulting easting as seen +below:: + + $ proj +proj=merc +lon_0=110 + -70 0 + -20037508.34 0.00 + 290 0 + 20037508.34 0.00 + +From PROJ 5 on onwards, the same input now results in same coordinates, as seen +from the example below where PROJ 5 is used:: + + $ proj +proj=merc +lon_0=110 + -70 0 + -20037508.34 0.00 + 290 0 + -20037508.34 0.00 + +The change is made on the basis that :math:`\lambda=290^{\circ}` is a full +rotation of the circle larger than :math:`\lambda=-70^{\circ}` and hence +should return the same output for both. + +Adding the :option:`+over` flag to the projection definition provides +the old behaviour. diff --git a/docs/source/usage/index.rst b/docs/source/usage/index.rst index 7de0e147..823e8fe7 100644 --- a/docs/source/usage/index.rst +++ b/docs/source/usage/index.rst @@ -16,4 +16,4 @@ command line applications or the C API that is a part of the software package. projections transformation environmentvars - + differences |