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We're gearing up to support GDA2020

Did you know Australia moves 7cm each year? That’s right – Australia has drifted 1.6 metres to the north-east since 1994. No wonder I can never find my car keys!

It might not seem like much, but at Spookfish, we take accuracy very seriously and so do our customers. It can make a huge difference when you’re viewing imagery with other spatial data, like property boundaries, asset locations or design plans. If these datasets don’t accurately reflect their real-world position, one uninformed decision could lead to a costly mistake.

To ensure all spatial data is accurately positioned, the Australian Government is releasing GDA2020, Australia's new official national datum.

To support GDA2020, there’s a few changes we’ll soon be implementing in our MapViewer, Web Map Tile Service and Web Map Service.

Upcoming changes to MapViewer

With the implementation of GDA2020 in the Spookfish MapViewer:

  • All of our customers will see improvements to the accuracy of property boundaries.
  • OrthoFlex customers will be able to choose one of the eight MGA zones in GDA2020 when exporting a selected area. The existing GDA94 and WGS84 Spherical Mercator options will also remain in place.

These changes will take effect on 2nd July 2018.

Upcoming changes to Web Map Tile Service (WMTS)

The Spookfish WMTS has historically provided a choice of two layers:

  • Web Mercator projection; and
  • An alternate grid configuration for GDA94 alignment.

We'll continue to provide both layers, so if you want to continue to use GDA94, you’ll still be able to do that. However, we are making some changes to the way we calculate the GDA94-aligned layer.

These changes will mean that we achieve GDA94 alignment by using a simple 2 parameter (eastings & northings) shift of the entire grid system in the opposite direction to the motion of the continental plate. This change in the grid system serves to roughly undo the shift Australia has made between 1994 and 2020.

There's a couple of important points to note:

  • As the continent does not move uniformly, the shift values used are approximate. The shift values have been derived by averaging the motion across a set of sample points. So in some areas, the shift will be more accurate than other areas.
  • The data itself will continue to be projected using the Web Mercator projection, not MGA zones.

For use cases where web service performance is more important than accuracy, we recommend our Web Map Tile Service. For higher accuracy or MGA zone-based data, we recommend our Web Map Service.

These changes will take effect on 2nd July 2018.

Upcoming changes to Web Map Service (WMS)

The Spookfish WMS has historically provided two layer groups:

  • ITRF; and
  • GDA94

You can see these two layer groups in the current WMS layer structure:

Current WMS Layer Structure

To bring our WMS in line with industry standards, we’re phasing out the “ITRF” and “GDA94” layer groups.

From 2nd July 2018, imagery alignment will be based on your selected spatial reference system. We’re introducing new layers at the root level to facilitate this change. When you add these new layers to an existing project or map template, your spatial client will intuitively recognise the correct projection and apply it. If there is no pre-existing projection in place, you’ll need to specify the projection when you add the layer to your spatial client.

Here’s an example of the layer structure that will be available from 2nd July 2018. Layers shaded red indicate the old layer groups, which will remain available during a one-month transition period. Layers shaded green indicate the new layers which WMS users will need to migrate to before 2nd August 2018.

WMS Layer Structure from 2nd July 2018

WMS users will need to migrate to the new layers before 2nd August 2018, at which point we’ll remove the “GDA94” and “ITRF” layer groups.

Here’s an example of the layer structure that will be available from 2nd August 2018:

WMS Layer Structure from 2nd August 2018

We're here to help

There’s a lot we’ve covered off in this article, but our team is available to assist. If you have questions or feedback, please comment below or drop us a line.

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