From 15a225b0d80281b80c536e7b5dde334d12c406c6 Mon Sep 17 00:00:00 2001 From: Kristian Evers Date: Fri, 1 Feb 2019 12:59:44 +0100 Subject: Remove +t_obs parameter from helmert operation --- docs/source/operations/transformations/helmert.rst | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) (limited to 'docs') diff --git a/docs/source/operations/transformations/helmert.rst b/docs/source/operations/transformations/helmert.rst index 5451c3d1..51784bdb 100644 --- a/docs/source/operations/transformations/helmert.rst +++ b/docs/source/operations/transformations/helmert.rst @@ -41,10 +41,7 @@ The kinematic transformations require an observation time of the coordinate, as as a central epoch for the transformation. The latter is usually documented alongside the rest of the transformation parameters for a given transformation. The central epoch is controlled with the parameter `t_epoch`. The observation -time can either by stated as part of the coordinate when using PROJ's -4D-functionality or it can be controlled in the transformation setup by the -parameter `t_obs`. When `t_obs` is specified, all transformed coordinates are -treated as if they have the same observation time. +time is given as part of the coordinate when using PROJ's 4D-functionality. Examples +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ @@ -62,16 +59,16 @@ Simplified transformations from ITRF2008/IGS08 to ETRS89 using 7 parameters: proj=helmert convention=coordinate_frame x=0.67678 y=0.65495 z=-0.52827 rx=-0.022742 ry=0.012667 rz=0.022704 s=-0.01070 -Transformation from `ITRF2000@2017.0` to `ITRF93@2017.0` using 15 parameters: +Transformation from `ITRF2000` to `ITRF93` using 15 parameters: :: - proj=helmert convention=position_vector + proj=helmert convention=position_vector x=0.0127 y=0.0065 z=-0.0209 s=0.00195 dx=-0.0029 dy=-0.0002 dz=-0.0006 ds=0.00001 rx=-0.00039 ry=0.00080 rz=-0.00114 drx=-0.00011 dry=-0.00019 drz=0.00007 - t_epoch=1988.0 t_obs=2017.0 + t_epoch=1988.0 Parameters +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ @@ -178,13 +175,6 @@ Parameters Central epoch of transformation given in decimalyear. Only used spatiotemporal transformations. -.. option:: +t_obs= - - Observation time of coordinate(s) given in decimalyear. Mostly useful - in 2D and 3D transformations where the observation time is not passed - as part of the input coordinate. Can be used to override the observation - time from the input coordinate. - .. option:: +exact Use exact transformation equations. -- cgit v1.2.3 From 29a59cadb9d1371479477af517f3431784e880f9 Mon Sep 17 00:00:00 2001 From: Kristian Evers Date: Thu, 14 Feb 2019 12:00:45 +0100 Subject: Reverse direction of deformation operations/transformations/deformation Changed the direction of dt-calculation to follow the same convention as helmert. Changed from dt = t_c - t_obs to dt = t_obs - t_c, which effectively reverses the direction of the operation. Existing projstrings using deformation can simply reverse the direction of the operation to achieve the same results as before this commit. --- .../operations/transformations/deformation.rst | 20 ++++++++++---------- docs/source/usage/differences.rst | 22 ++++++++++++++++++++++ 2 files changed, 32 insertions(+), 10 deletions(-) (limited to 'docs') diff --git a/docs/source/operations/transformations/deformation.rst b/docs/source/operations/transformations/deformation.rst index 87b08453..0a772547 100644 --- a/docs/source/operations/transformations/deformation.rst +++ b/docs/source/operations/transformations/deformation.rst @@ -127,7 +127,7 @@ Mathematically speaking, application of a deformation model is simple. The defor represented as a grid of velocities in three dimensions. Coordinate corrections are applied in cartesian space. For a given coordinate, :math:`(X, Y, Z)`, velocities :math:`(V_X, V_Y, V_Z)` can be interpolated from the gridded model. The time span -between :math:`t_c` and :math:`t_{obs}` determine the magnitude of the coordinate +between :math:`t_{obs}` and :math:`t_c` determine the magnitude of the coordinate correcton as seen in eq. :eq:`apply_velocity` below. .. math:: @@ -144,7 +144,7 @@ correcton as seen in eq. :eq:`apply_velocity` below. Y \\ Z \\ \end{pmatrix}_A + - (t_c - t_{obs}) + (t_{obs} - t_c) \begin{pmatrix} V_X \\ V_Y \\ @@ -154,14 +154,14 @@ correcton as seen in eq. :eq:`apply_velocity` below. Corrections are done in cartesian space. -Coordinates of the gridded model are in ENU (east, north, up) space because it would -otherwise require an enormous 3 dimensional grid to handle the corrections in cartesian -space. Keeping the correction in lat/long space reduces the complexity of the grid -significantly. Consequently though, the input coordinates needs to be converted to -lat/long space when searching for corrections in the grid. This is done with the *cart* -operation. The converted grid corrections can then be applied to the input coordinates -in cartesian space. The conversion from ENU space to cartesian space is done in the -following way: +Coordinates of the gridded model are in ENU (east, north, up) space because it +would otherwise require an enormous 3 dimensional grid to handle the corrections +in cartesian space. Keeping the correction in lat/long space reduces the +complexity of the grid significantly. Consequently though, the input coordinates +needs to be converted to lat/long space when searching for corrections in the +grid. This is done with the :ref:`cart` operation. The converted grid +corrections can then be applied to the input coordinates in cartesian space. The +conversion from ENU space to cartesian space is done in the following way: .. math:: :label: enu2xyz diff --git a/docs/source/usage/differences.rst b/docs/source/usage/differences.rst index 5694e4d0..caab865c 100644 --- a/docs/source/usage/differences.rst +++ b/docs/source/usage/differences.rst @@ -69,3 +69,25 @@ Before PROJ 6, the proj_def.dat was used to provide general and per-projection parameters, when +no_defs was not specified. It has now been removed. In case, no ellipsoid or datum specification is provided in the PROJ string, the default ellipsoid is GRS80 (was WGS84 in previous PROJ versions). + +Changes to :ref:`deformation` +------------------------------------------------------------------ + +In the initial version of the of :ref:`deformation` operation the time span between :math:`t_{obs}` and :math:`t_c` was determine by the expression + +.. math:: + + dt = t_c - t_{obs} + +With version 6.0.0 this has been reversed in order to behave similarly to +the :ref:`Helmert operation`, which determines time differences as + +.. math:: + + dt = t_{obs} - t_c + +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. -- cgit v1.2.3 From 82855db893dd66de9588497e5748e64a9622ea66 Mon Sep 17 00:00:00 2001 From: Kristian Evers Date: Thu, 14 Feb 2019 12:08:13 +0100 Subject: Cosmetical changes to differences.rst --- docs/source/usage/differences.rst | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'docs') diff --git a/docs/source/usage/differences.rst b/docs/source/usage/differences.rst index caab865c..b7c79f53 100644 --- a/docs/source/usage/differences.rst +++ b/docs/source/usage/differences.rst @@ -65,8 +65,8 @@ Version 6.0.0 Removal of proj_def.dat ----------------------- -Before PROJ 6, the proj_def.dat was used to provide general and per-projection -parameters, when +no_defs was not specified. It has now been removed. In case, +Before PROJ 6, the ``proj_def.dat`` was used to provide general and per-projection +parameters, when ``+no_defs`` was not specified. It has now been removed. In case, no ellipsoid or datum specification is provided in the PROJ string, the default ellipsoid is GRS80 (was WGS84 in previous PROJ versions). -- cgit v1.2.3 From 12689e3d858d66e5e00e8d99f9326ef91cc0a384 Mon Sep 17 00:00:00 2001 From: Kristian Evers Date: Thu, 14 Feb 2019 14:51:39 +0100 Subject: deformation: Replace +t_obs with +dt 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 +dt has been added for that purpose. The new parameter is mutually exclusive with +t_epoch. +dt is used when deformation for a set amount of time is needed and +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. --- .../operations/transformations/deformation.rst | 38 ++++++++++++++-------- docs/source/usage/differences.rst | 27 +++++++++++++-- 2 files changed, 49 insertions(+), 16 deletions(-) (limited to 'docs') diff --git a/docs/source/operations/transformations/deformation.rst b/docs/source/operations/transformations/deformation.rst index 0a772547..3a9d025c 100644 --- a/docs/source/operations/transformations/deformation.rst +++ b/docs/source/operations/transformations/deformation.rst @@ -31,9 +31,9 @@ they represent the physical world better. In PROJ this is done with the deformat operation. The horizontal grid is stored in CTable2 format and the vertical grid is stored in the -GTX format. Both grids are expected to contain grid-values in units of mm/year. -Details about the formats can be found in the GDAL documentation. GDAL both reads and -writes both file formats. Using GDAL for construction of new grids is recommended. +GTX format. Both grids are expected to contain grid-values in units of +mm/year. GDAL both reads and writes both file formats. Using GDAL for +construction of new grids is recommended. Example ------------------------------------------------------------------------------- @@ -59,13 +59,14 @@ to the Danish realisation of ETRS89 is in PROJ described as:: step proj = deformation t_epoch = 2000.0 xy_grids = ./nkgrf03vel_realigned_xy.ct2 z_grids = ./nkgrf03vel_realigned_z.gtx + inv # NKG_ETRF@2000.0 -> ETRF92@2000.0 step proj=helmert convention=position_vector s = -0.009420e x = 0.03863 rx = 0.00617753 y = 0.147 ry = 5.064e-05 z = 0.02776 rz = 4.729e-05 # ETRF92@2000.0 -> ETRF92@1994.704 - step proj = deformation t_epoch = 1994.704 t_obs = 2000.0 + step proj = deformation dt = -5.296 xy_grids = ./nkgrf03vel_realigned_xy.ct2 z_grids = ./nkgrf03vel_realigned_z.gtx @@ -86,10 +87,6 @@ component. Parameters ------------------------------------------------------------------------------- -Required -################################################################################ - - .. option:: +xy_grids= Comma-separated list of grids to load. If a grid is prefixed by an `@` the @@ -110,15 +107,22 @@ Required .. option:: +t_epoch= - Central epoch of transformation given in decimalyears. + Central epoch of transformation given in decimalyears. Will be used in + conjunction with the observation time from the input coordinate to + determine :math:`dt` as used in eq. :eq:`apply_velocity` below. + + .. note:: :option:`+t_epoch` is mutually exclusive with :option:`+dt` + +.. option:: +dt= -Optional -################################################################################ + .. versionadded:: 6.0.0 -.. option:: +t_obs= + :math:`dt` as used in eq. :eq:`apply_velocity` below. Is useful when + no observation time is available in the input coordinate or when + a deformation for a specific timespan needs to be applied in a + transformation. :math:`dt` is given in units of decimalyears. - Observation time of coordinate(s) given in decimalyears. If not specified, - the observation time from the temporal component of 4D input points is used. + .. note:: :option:`+dt` is mutually exclusive with :option:`+t_epoch` Mathematical description ------------------------------------------------------------------------------- @@ -182,3 +186,9 @@ conversion from ENU space to cartesian space is done in the following way: where :math:`\phi` and :math:`\lambda` are the latitude and longitude of the coordinate that is searched for in the grid. :math:`(E, N, U)` are the grid values in ENU-space and :math:`(X, Y, Z)` are the corrections converted to cartesian space. + + +See also +----------------------------------------------------------------------------- + +#. :ref:`Behavioural changes from version 5 to 6` \ No newline at end of file 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` ------------------------------------------------------------------ +.. _differences_deformation: -In the initial version of the of :ref:`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` 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 -- cgit v1.2.3