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About TerraFlex Project Geodetics in Trimble Positions Desktop add-in and the TerraFlex Desktop add-in 

29 days ago

Introduction

New in Trimble Positions Desktop add-in v10.8.1.1 and the TerraFlex Desktop add-in v5.0 is the ability to configure TerraFlex workflows using local coordinate systems. For the most part, the ability to create a TerraFlex project that uses a local coordinate system is dependent on:

  1. The coordinate system used by the feature classes in the geodatabase.
  2. The curated set of coordinate systems that are supported in TerraFlex v5.
  3. The coordinate systems referenced by the correction sources (sources of accuracy; in real-time or post-processing).

We have tried to put as much of the coordinate system information as possible in one place - a new wizard page during project setup called Project Geodetics. The text below describes the options available on this page, with the same content being available from within the app by clicking on the Click here for more details about geodetic settings link on the wizard page itself.

Project Wizard: Project Geodetics

Geodatabase Coordinate System (horizontal)

The Esri ArcGIS definition of the horizontal coordinate system used by the geodatabase feature classes in the project, expressed in its individual components.
Coordinate System: Esri name of the coordinate system used in the geodatabase feature classes
Geographic Coordinate System: Esri name of the underlying geographic coordinate system used in the geodatabase feature classes
Datum: Esri name of the datum referenced in the underlying geographic coordinate system used in the geodatabase feature classes
Matching Trimble Datum (if any): Trimble name of the equivalent Trimble datum

Map Coordinate System

The Esri ArcGIS definition of the horizontal coordinate system used in the data frame of the map document for display.
Coordinate System: Esri name of the coordinate system used in the map document data frame
Geographic Coordinate System: Esri name of the underlying geographic coordinate system used in the map document data frame

Geodetic Workflow

Geodetic workflow defines the way GNSS coordinates are stored in the Terraflex and Positions and how are converted when required. Depending on the geodatabase coordinate system above, the following geodetic workflows are available:

  • Classic (store GNSS as WGS 1984)
    Store all position data in TerraFlex and Positions in the global WGS 1984 datum and apply transformations wherever required. Best used when the datum of the correction source does not match that of the project. Transformations in the field-side of the workflow will be done with Trimble components while transformations in the office-side of the workflow will be done with Esri ArcGIS components (see next section).

    Real-time Accuracy Source
    Corrected positions from local sources (VRS, RTK) will be transformed between their datum (as specified) and that of the project using standard methods. Corrected positions from global sources (RTX and SBAS) will not be transformed.

    Post-processed Accuracy Source
    Post-processing will use base station reference positions in the global WGS 1984 datum and results will be transformed to the project datum. This is affected by the ‘Handling for differential correction’ setting on the ‘Reference Position’ tab of the ‘Base Station Properties’ dialog (editable for user base stations). See this article for more information.

    Datum Transformation for geodatabase: Esri name of the geographic coordinate system (datum) transformation used to store features in the geodatabase feature classes
    Datum Transformation for map: Esri name of the geographic coordinate system (datum) transformation used to display features in the map document data frame

  • Minimize Transformations (store GNSS as <Trimble name of the supported, matched datum> [Esri name: <Esri name of the supported, matched datum>])
    Store all position data in TerraFlex and Positions in the supported local datum and thus minimize the number of datum transformations required in the whole workflow. Best used when all correction sources share the same datum as the project OR when using Trimble RTX.

    Real-time Accuracy Source
    Corrected positions from global sources (RTX and SBAS) will be transformed using the most accurate, time-dependent methods. Corrected positions from local sources (VRS, RTK) will not be transformed and as a result, only those that specify the same datum can be included with the project.

    Post-processed Accuracy Source
    Post-processing will use base station reference positions that match the local datum and results will not be transformed. Only base stations that have reference positions in the local datum will be usable for post-processing. This is affected by the ‘Handling for differential correction’ setting on the ‘Reference Position’ tab of the ‘Base Station Properties’ dialog (editable for user base stations). See this article for more information.

  • Use a Standard Reference Frame (store GNSS as <Trimble name of the supported, standard datum> [Esri name: <Esri name of the supported, standard datum>])
    Store all position data in TerraFlex and Positions in the supported local datum but allow office-side transformations between the project’s local coordinate system and that of the geodatabase using Esri ArcGIS components (see next section). This option is only available for select regions where the use of related local coordinate systems is common.

    Real-time Accuracy Source
    Corrected positions from global sources (RTX and SBAS) will be transformed using the most accurate, time-dependent methods. Corrected positions from local sources (VRS, RTK) will not be transformed and as a result, only those that specify the same datum can be included with the project.

    Post-processed Accuracy Source
    Post-processing will use base station reference positions that match the storage datum and results will be transformed to the alternate local datum used in the geodatabase. Only base stations that have reference positions in the storage datum will be usable for post-processing. This is affected by the ‘Handling for differential correction’ setting on the ‘Reference Position’ tab of the ‘Base Station Properties’ dialog (editable for user base stations). See this article for more information.

    Datum Transformation for geodatabase: Esri name of the geographic coordinate system (datum) transformation used to store features in the geodatabase feature classes
    Datum Transformation for map: Esri name of the geographic coordinate system (datum) transformation used to display features in the map document data frame

About Esri ArcGIS Datum Transformations

Based on the Geodetic Workflow setting and the way datums and datum transformations are modeled in Esri ArcGIS components, it may be necessary to select the following datum transformations:

  • Transformation for geodatabase (storage)
    The datum transformation that will be used to transform between Positions and geodatabase feature geometries coordinates at the time features are stored or retrieved to/from geodatabase.
  • Transformation for map (display)
    The datum transformation that will be used to display Positions feature geometries and positions (in a session) as temporary graphic elements on the map document data frame.

TerraFlex Project Coordinate System (horizontal)

The coordinate system that will be used for the project in both the TerraFlex mobile application and the Connect Map Viewer web application (where it is known as a workspace). This affects storage of data as well as coordinate display, measurement, and navigation.
Note: Projected coordinate systems will be more fully supported in a future release of Positions.
Coordinate System: Trimble name of the coordinate system to be used in the TerraFlex workflow

Feature heights (vertical)

The setting for how feature heights should be handled both field-side in TerraFlex and office-side in Positions. This affects both feature height metadata and the Z component of geometries in 3D, or Z-enabled feature classes.

  • Use height above ellipsoid (HAE)
    Store all feature heights and Z values as-is, without conversion from the GNSS (as height-above- ellipsoid)
  • Use height above mean sea level (MSL)
    Convert feature heights and Z values from height-above-ellipsoid to an orthometric height (typically called MSL) by using the Trimble geoid model selected. Geoids available are filtered based on the current extents of the map in view.
  • Use fixed separation (meters, office only)
    Store all feature heights and Z values with a fixed separation value (in meters) applied to the height-above-ellipsoid value. This is only available in the office-side workflow in Positions (values in TerraFlex will remain height-above-ellipsoid).

For More Information

For more information on geodetics related to high-accuracy GIS data collection workflows, consult this site.

#terraflex
#positions
#trimble_positions
#esri
#arcgis
#arcmap

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