diff options
Diffstat (limited to 'docs/source/usage')
| -rw-r--r-- | docs/source/usage/differences.rst | 27 |
1 files changed, 25 insertions, 2 deletions
diff --git a/docs/source/usage/differences.rst b/docs/source/usage/differences.rst index b7c79f53..d5eebe8e 100644 --- a/docs/source/usage/differences.rst +++ b/docs/source/usage/differences.rst @@ -72,8 +72,15 @@ default ellipsoid is GRS80 (was WGS84 in previous PROJ versions). Changes to :ref:`deformation<deformation>` ------------------------------------------------------------------ +.. _differences_deformation: -In the initial version of the of :ref:`deformation<deformation>` operation the time span between :math:`t_{obs}` and :math:`t_c` was determine by the expression + +Reversed order of operation +........................... + +In the initial version of the of :ref:`deformation<deformation>` operation +the time span between :math:`t_{obs}` and :math:`t_c` was determined by the +expression .. math:: @@ -90,4 +97,20 @@ Effectively this means that the direction of the operation has been reversed, so that what in PROJ 5 was a forward operation is now an inverse operation and vice versa. -Pipelines written for PROJ 5 can be migrated to PROJ 6 by adding :option:`+inv` to forward steps involving the deformation operation. Similarly :option:`+inv` should be removed from inverse steps to be compatible with PROJ 6. +Pipelines written for PROJ 5 can be migrated to PROJ 6 by adding :option:` ++inv` to forward steps involving the deformation operation. Similarly +:option:`+inv` should be removed from inverse steps to be compatible with +PROJ 6. + +Removed ``+t_obs`` parameter +............................. + +The ``+t_obs`` parameter was confusing for users since it effectively +overwrote the observation time in input coordinates. To make it more clear +what is the operation is doing, users are now required to directly specify +the time span for which they wish to apply a given deformation. The parameter +:option:`+dt` has been added for that purpose. The new parameter is mutually +exclusive with :option:`+t_epoch`. :option:`+dt` is used when deformation +for a set amount of time is needed and :option:`+t_epoch` is used (in +conjunction with the observation time of the input coordinate) when +deformation from a specific epoch to the observation time is needed.
\ No newline at end of file |