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我要补充2个纵坐标系统添加到FME
These are:
WKID 6647(CGVD 2013)正高
WKID 5713 (CGND 1928) Normal-orthometric*
我都在.byn格式所需要的网格文件和安装,我才明白,能够与CSReprojector工作。
我试图使用在线Define Custom Coordinate System从FME创建自定义坐标系为6647和5713.我有需要,但是我无法提交,因为我需要一个参考基准的ESRI WKT信息。
However the datum is vertical and is:
Canadian_Geodetic_Vertical_Datum_of_2013
和
Canadian_Geodetic_Vertical_Datum_of_1928
And does not appear in the list of Datum's.
How do I do this, do I even need to or are the .byn files enough when working with the CSMapReprojector?
第二个进一步的问题是CSMapReprojector询问"Vertial handling" as seen here。随着像“地心或椭圆形的高度 - >正高”项目。
不过我有:正常,正高* - >正高
*普通正高(Hno):这个术语是不合适的,但是it is used to define the type of heights associated with CGVD28. These heights are neither orthometric nor normal, i.e., they are not compatible with the geoid or quasi-geoid. They are determined using normal gravity, but they are based on the formulation of orthometric heights. Normal orthometric heights were used in Canada because no actual gravity measurements were available at the time of the realization of CGVD28. The objective of the 1928 adjustment was the determination of the most accurate orthometric heights, which explains why they are commonly referred as orthometric heights. (Unit: m) -NRCAN
Hi@tforward,
In FME's present coordinate system handling, vertical datums are not part of the coordinate system definitions, but are handled separately in the Vertical section of the CsmapReprojector.
The transformer assumes that the supplied vertical grid is designed to convert the heights from the ellipsoid to orthometric, so if you choose 'Geocentric or ellipsoid height -> Orthometric height', the grid will be applied in the forward direction, while 'Orthometric height -> Geocentric or ellipsoid height' will apply it in reverse. I think the CGVD28 grid will work OK, even though it is not truly Orthometric, however you may wish to test on some known points first.
所述.byn文件可以用于垂直变换,但不能在CsmapReprojector直接选择。为了允许多个网格文件被用于转化,FME使用网格目录文件(.gdc),这是包含相关GRD文件的路径的ASCII FIE。有关创建该文件的详细信息,请参阅https://docs.亚搏在线safe.com/fme/html/FME_Desktop_Documentation/FME_Coordinate_Systems/CoordSys/vertical_grids.htm。This .gdc file is chosen for the Geoid Height Grid setting in the CsmapReprojector.
@daveatsafe Thank you Dave for the quick response, much appreciated.
Just to clarify, I should try using 'Orthometric height -> Geocentric or ellipsoid height' within the CSMapReprojector?
Secondly, as per the .byn files within CSMapReprojector. I do also have a HT2_2010v70_CGG2013a.byn which Conversion grids between CGVD28 and CGVD2013 off the top of your head, do you think this would be all I would need to put into the CSMapReprojector? Best, Tristan
Hi@tforward,
You will still need to create the .gdc containing the path to the .byn file, which is what you choose as the grid file in the CsmapReprojector.
For the HT2_2010v70_CGG2013a grid, please use 'Geocentric or ellipsoid height -> Orthometric height' when converting from CGVD28 to CGVD2013, and 'Orthometric height -> Geocentric or ellipsoid height' for the reverse.
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