From 6d1a1ff4e470bb4d26be46bdf01de3d94e6ab8e9 Mon Sep 17 00:00:00 2001 From: Kristian Evers Date: Mon, 18 Sep 2017 22:21:20 +0200 Subject: Moved projection list to using chapter and created a list of transformations. Both are grouped in a section called operations. --- .../operations/transformations/vgridshift.rst | 34 ++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100644 docs/source/usage/operations/transformations/vgridshift.rst (limited to 'docs/source/usage/operations/transformations/vgridshift.rst') diff --git a/docs/source/usage/operations/transformations/vgridshift.rst b/docs/source/usage/operations/transformations/vgridshift.rst new file mode 100644 index 00000000..f48d40c8 --- /dev/null +++ b/docs/source/usage/operations/transformations/vgridshift.rst @@ -0,0 +1,34 @@ +.. _vgridshift: + +================================================================================ +Vertical grid shift +================================================================================ + +Change Vertical datum change by grid shift + ++--------------+--------------------------------------------------------------------+ +| **Options** | ++--------------+--------------------------------------------------------------------+ +| `+grids` | Comma-separated list of grids to load. | ++--------------+--------------------------------------------------------------------+ + +The vertical grid shift is done by offsetting the vertical input coordinates by +a specific amount determined by the loaded grids. The simplest use case of the +horizontal grid shift is applying a single grid. Here we change the vertical +reference from the ellipsoid to the global geoid model, EGM96:: + + +vgridshift +grids=egm96_16.gtx + + +More than one grid can be loaded at the same time, for instance in the case where +a better geoid model than the global is available for a certain area. Here the +gridshift is set up so that the local DVR90 geoid model takes presedence over +the global model:: + + +vgridshift +grids=@dvr90.gtx,egm96_16.gtx + +The ``@`` in the above example states that the grid is optional, in case the grid +is not found in the PROJ.4 search path. The list of grids is prioritized so that +grids in the start of the list takes presedence over the grids in the back of the +list. + -- cgit v1.2.3