How To: Prepare FME workbenches for SLIP moving to GDA2020 – Help Centre

FME workbenches that extract data from web services will potentially be impacted by the GDA2020 implementation, however, this will depend on how the workbench is structured. We have developed the advice below as a potential solution that can be implemented immediately.

Please note: Using data downloads extracts is a more reliable option in this scenario rather than extracting via services. Please see https://toolkit.data.wa.gov.au/hc/en-gb/articles/115000962734-How-To-Download-Geospatial-Data-Snapshots for more information.

Example Scenario – Simple FME workbench extract misalignment due to GDA2020 change

We have used a basic script that takes an extract of an area of interest and saves it to a local file geodatabase.

In this example we are applying an input geometry polygon to set the Area of Interest (AOI).

The workbench is writing directly to a file geodatabase leaving the output projection the same as the source. As the source datum will change when the GDA2020 implementation occurs this will cause a misalignment for those wanting to continue working in the current datum.

The image below displays the resulting misalignment that occurs between an extract from the SLIP UAT (EPSG:7844) and the SLIP PROD (EPSG:3857) environments.

Solution

A relatively easy solution to this is to add a process to test and reproject to the desired datum (in this case we have set the output to EPSG:3857). (Details of each transformer setting can be found at “Transformer Settings” section)

This additional process can be combined as a custom transformer and then added to each layer being called in the workbench by cutting and pasting.

A sample version of this custom transformer can be found at https://github.com/datawagovau/fme-workbenches/tree/master/GDA2020-slip-services-reproject

This will enable the output to remain consistent regardless of whether the service is 3857 or 7844 (See example below). This can be implemented immediately and will mean when the updated GDA2020 service goes live no further change will be required.

Comparison of reprojected UAT and reprojected PROD to existing PROD shows consistent alignment: