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What does the CS-Map v13 upgrade mean for me?
By default,FME uses CS-Map for reprojecting,or converting geometry between coordinate systems.CS-Map has traditionally forced the use of a single datum shift (also called the transformation or geotransformation) when converting between coordinate systems in different datums.It has also used a "pivot datum",i.e.a transformation from Datum A to Datum B would be executed as A -> WGS84 -> B.These properties may be beneficial for usability,since users are less likely to make incorrect or inconsistent choices,but they aren't desirable when multiple choices for datum shifts are required,or when it isn't appropriate to use WGS84 as an intermediate datum.In FME 2013,CS-Map has been upgraded to version 13.In the v13 release,the CS-Map datum transformation approach has become more standards-compliant,and closer to EPSG and ArcGIS.Rather than forcing the selection of a single transformation for each pair of datums,users can now pick the datum shift.This is critical in cases where there is more than one valid way to convert between different datums,and the correct one must be chosen based on context.Transformations also no longer depend on the WGS84 pivot.Further,CS-Map v13 provides more flexibility in defining grid shift-based transformations.For a more detailed discussion on this,visit this blog post onIt's All About Data.Alongside this upgrade is the more flexible ability to choose which U.S.or Canadian grid files to use when converting between the NAD27 and NAD83 datums.
Old workspaces will be backward-compatible,and will function the same as they always have.
New workspaces give you the ability to choose a datum transformation yourself.This can be done within theCsmapReprojectortransformer parameters.
You can type the name of the desired datum shift,view automatic suggestions,or browse the full list of transformations in the Geographic Transformation Gallery.
Note there are single-step transformations as well as multi-step paths,which are made of of chains of single-step transformations.Here you can also specify Canadian and U.S.variants of the NAD27/83 transformation.
If you do not choose a datum transformation,FME will choose one automatically using an algorithm that makes a best guess based on the source and destination coordinate systems.This is called an implicit transformation,or implicit reprojection.Previously,the same datum transformation was always used between two coordinate systems.Now,since FME uses the transformation chosen by an algorithm,users should be aware that this choice may change over time.Manually choosing a datum transformation avoids this.
The chosen implicit transformations can be overridden by adding entries to TransformationExceptions.db,which is located in
You can modify grid-based transformation definitions in Tools > FME Options > Coordinate Systems.Notable improvements include the ability to:
1.Pick any grid format you want for any transformation,and use combinations of formats if desired.
2.Choose the precedence of the grid files for a transformation with more than one grid.
3.Specify the direction the grid operates in.
4.Easily see the grid changes you've made and revert them if desired.Note that administrative privileges are not required,as overrides are stored at user-level in the user's Documents folder.These grid overrides apply to all installed copies of FME that support grid overrides.
5.Choose Canada or U.S.datum shift for implicit transformations,set on a per-user basis.Previously this could only be set during the FME installation and only affected that copy of FME.
To choose Canada or U.S.datum shift for implicit transformations see theFME Server Administrator's Guide.
There is no interface for configuring explicit Grid Transformation Definitions.Instead you must define it in Workbench like above and then:
Creating World Files from Georeferenced Rasters
NAD27 NAD83 Datum Shifts In US and Canada
Where to source Canadian grid shift files not included with FME
Spherical or Web Mercator Coordinate System
Canadian Spatial Reference System (CSRS) High Precision Datum
Oracle Coordinate System Support
Distance Measurements with the GeographicLengthCalculator
Explanation of the Coordinate Systems Exceptions Folder in FME Desktop
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