diff options
Diffstat (limited to 'docs/source/development/reference')
| -rw-r--r-- | docs/source/development/reference/datatypes.rst | 79 |
1 files changed, 40 insertions, 39 deletions
diff --git a/docs/source/development/reference/datatypes.rst b/docs/source/development/reference/datatypes.rst index f2f1d9c9..7f2c4b41 100644 --- a/docs/source/development/reference/datatypes.rst +++ b/docs/source/development/reference/datatypes.rst @@ -4,7 +4,7 @@ Data types ================================================================================ -This section describe the multiplude of data types in use in PROJ.4. As a rule +This section describes the numerous data types in use in PROJ.4. As a rule of thumb PROJ.4 data types are prefixed with ``PJ_``, or in one particular case, is simply called :c:type:`PJ`. A few notable exceptions can be traced back to the very early days of PROJ.4 when the ``PJ_`` prefix was not @@ -16,8 +16,8 @@ Transformation objects .. c:type:: PJ Object containing everything related to a given projection or transformation. - As a user of the PROJ.4 library your are only exposed to pointers to this - object and the contents are hidden in the public API. :c:type:`PJ` objects + As a user of the PROJ.4 library you are only exposed to pointers to this + object and the contents is hidden behind the public API. :c:type:`PJ` objects are created with :c:func:`proj_create` and destroyed with :c:func:`proj_destroy`. @@ -51,7 +51,7 @@ Transformation objects .. c:type:: PJ_CONTEXT - Context objects enables safe multi-threaded usage of PROJ.4. Each :c:type:`PJ` + Context objects enable safe multi-threaded usage of PROJ.4. Each :c:type:`PJ` object is connected to a context (if not specified, the default context is used). All operations within a context should be performed in the same thread. :c:type:`PJ_CONTEXT` objects are created with :c:func:`proj_context_create` @@ -97,11 +97,11 @@ Various 2-dimensional coordinate data types. typedef struct { double x, y; } PJ_XY; - .. c:member:: double PJ_XY.lam + .. c:member:: double PJ_XY.x Easting. - .. c:member:: double PJ_XY.phi + .. c:member:: double PJ_XY.y Northing. @@ -134,7 +134,7 @@ types above. .. c:type:: PJ_LPZ 3-dimensional version of :c:type:`PJ_LP`. Holds longitude, latitude and - vertical component. + a vertical component. .. code-block:: C @@ -163,15 +163,15 @@ types above. .. c:member:: double PJ_XYZ.x - Easting. + Easting or the X component of a 3D cartesian system. .. c:member:: double PJ_XYZ.y - Northing. + Northing or the Y component of a 3D cartesian system. .. c:member:: double PJ_XYZ.z - Vertical component. + Vertical component or the Z component of a 3D cartesian system. .. c:type:: PJ_UVW @@ -249,15 +249,15 @@ domain. .. c:member:: double PJ_XYZT.x - Easting. + Easting or the X component of a 3D cartesian system. .. c:member:: double PJ_XYZT.y - Northing. + Northing or the Y component of a 3D cartesian system. .. c:member:: double PJ_XYZT.z - Vertical component. + Vertical or the Z component of a 3D cartesian system. .. c:member:: double PJ_XYZT.t @@ -320,7 +320,7 @@ Complex coordinate types .. c:type:: PJ_COORD - General purpose coordinate union type usefull in two, three and four dimensions. + General purpose coordinate union type, applicable in two, three and four dimensions. This is the default coordinate datatype used in PROJ. .. code-block:: C @@ -385,9 +385,7 @@ Projection derivatives .. c:type:: PJ_FACTORS Various cartographic properties, such as scale factors, angular distortion - and meridian convergence. Calculated with :c:func:`proj_factors`. Depending - on the underlying projection, values can be calculated either numerically - or analytically. + and meridian convergence. Calculated with :c:func:`proj_factors`. .. code-block:: C @@ -434,13 +432,15 @@ Projection derivatives Meridian convergence at coordinate :math:`\left(\lambda,\phi\right)`. Sometimes also described as *grid declination*. + .. c:member:: double PJ_FACTORS.tissot_semimajor - Maximum scale error. + Maximum scale factor. .. c:member:: double PJ_FACTORS.tissot_semiminor - Minimum scale error. + Minimum scale factor. + .. c:member:: double PJ_FACTORS.dx_dlam @@ -449,7 +449,6 @@ Projection derivatives .. c:member:: double PJ_FACTORS.dy_dlam - Partial derivative :math:`\frac{\partial y}{\partial \lambda}` of coordinate :math:`\left(\lambda,\phi\right)`. @@ -460,7 +459,6 @@ Projection derivatives .. c:member:: double PJ_FACTORS.dy_dphi - Partial derivative :math:`\frac{\partial y}{\partial \phi}` of coordinate :math:`\left(\lambda,\phi\right)`. @@ -580,20 +578,20 @@ Info structures .. code-block:: C typedef struct { - char release[64]; - char version[64]; - int major; - int minor; - int patch; - char searchpath[512]; + int major; + int minor; + int patch; + const char *release; + const char *version; + const char *searchpath; } PJ_INFO; - .. c:member:: char PJ_INFO.release[64] + .. c:member:: const char *PJ_INFO.release Release info. Version number and release date, e.g. "Rel. 4.9.3, 15 August 2016". - .. c:member:: char PJ_INFO.version[64] + .. c:member:: const char *PJ_INFO.version Text representation of the full version number, e.g. "4.9.3". @@ -610,7 +608,7 @@ Info structures Patch level of release. - .. c:member:: char PJ_INFO.searchpath[512] + .. c:member:: const char PJ_INFO.searchpath Search path for PROJ. List of directories separated by semicolons (Windows) or colons (non-Windows), e.g. @@ -620,29 +618,32 @@ Info structures .. c:type:: PJ_PROJ_INFO Struct holding information about a :c:type:`PJ` object. Populated by - :c:func:`proj_pj_info`. + :c:func:`proj_pj_info`. The :c:type:`PJ_PROJ_INFO` object provides a + view into the internals of a :c:type:`PJ`, so once the :c:type:`PJ` + is destroyed or otherwise becomes invalid, so does the + :c:type:`PJ_PROJ_INFO` .. code-block:: C typedef struct { - char id[16]; - char description[128]; - char definition[512]; - int has_inverse; - double accuracy; + const char *id; + const char *description; + const char *definition; + int has_inverse; + double accuracy; } PJ_PROJ_INFO; - .. c:member:: char PJ_PROJ_INFO.id[16] + .. c:member:: const char *PJ_PROJ_INFO.id Short ID of the operation the :c:type:`PJ` object is based on, that is, what comes afther the ``+proj=`` in a proj-string, e.g. "*merc*". - .. c:member:: char PJ_PROJ_INFO.description[128] + .. c:member:: const char *PJ_PROJ_INFO.description Long describes of the operation the :c:type:`PJ` object is based on, e.g. "*Mercator Cyl, Sph&Ell lat_ts=*". - .. c:member:: char PJ_PROJ_INFO.definition[512] + .. c:member:: const char *PJ_PROJ_INFO.definition The proj-string that was used to create the :c:type:`PJ` object with, e.g. "*+proj=merc +lat_0=24 +lon_0=53 +ellps=WGS84*". |