GDA 2020 projection and missallignment issues with GDA94 and WGS84

I am having ongoing 1.5 metre misalignment issues between the new Australian GDA2020 projection that we have adopted in February 2020. The basic problem is that I run Geocortex in GDA 2020 (WKID7855) and all of my internally produced map services are in the same projection, however I need to consume some external organisation map services which are in GDA94 (WKID 4283) as they are a single point of truth and I wish to avoid duplication and inconsistencies as it is a legal dataset.

We are running SQL Server, ArcGIS Server v10.81, ArcMap v10.81 and Geocortex v4.14. Running anything through ArcMap is not a problem; if we drop our GDA2020 layers in first (this sets it to 7855) and then add some WGS84 layers, it all aligns fine which indicates ArcMap is not tricked by the WGS null transform issue.

The problem we have is related to Geocortex more than anything and a bit harder to solve. In Geocortex we can only consume map services and they come from internal and external sources, all of our internal sources reference GDA2020 transformed data that’s published in GDA2020 (WKID7855). The Geocortex install is also set to 7855 and it all works fine, however when we add an additional services in WGS84, they don’t align properly to the tune of approximately 1.5m. Australian based Geocortex support through AAM has consulted with VertiGIS yet it remains unsolved, ESRI Australia isn’t interested in it either. Basically from what I understand I can only play with the tips\tricks\tools that Geocortex allows me to use and thus far I have been unable to solve it.

Obviously I wish to consume these externally sourced layers from the point of truth\primary source and this is creating a bit of an issue in house as the last thing I wish to do is duplicate the layers.

[ Sample data for your reference https://maps.dubbo.nsw.gov.au/arcgis/rest/services/Portal_Maps/LPI_lots/MapServer misaligns with https://mapprod3.environment.nsw.gov.au/arcgis/rest/services/Planning/EPI_Primary_Planning_Layers/MapServer/2 ]

Further reading: The crux of the issue is The GDA2020/GDA94 null transform issue I refer to is detailed here (https://support.esri.com/en/technical-article/000017504) under the “GDA2020 and web GIS” section. This article (https://www.spatial.nsw.gov.au/__data/assets/pdf_file/0017/224432/NSW_GDA2020_AGRS_Policy.pdf) and this one ( https://icsm.gov.au/sites/default/files/GMIWG%20Advisory%20on%20WGS%2084%20and%20Web%20Mapping%20%E2%80%93%2015%20June%202020.pdf ) details the issues further.

Does anyone have any suggestions for my scenario?

Permanently deleted user

17 December 2021 04:22

Hi Nigel, I'm also interested in this questions related to use map services mixed with WGS84 (basically ESRIS's basemap) and GDA2020 datum. Have you get answers from VertiGIS or the local support team?

Nigel Christmas

20 December 2021 02:59

Unfortunately not yet. I'm still suffering the null transform issue as below but in reverse:

GDA2020 > (Tf: 7P 108060) > GDA94 > (Tf: NULL 1150) > WGS 84

Aside: WGS 84 input will remain untransformed… still an issue for services published as [WGS 84 = GDA94]

I was led to believe ArcGIS Server v10.9.1 was going to fix this null transform issue and I have only just got it loaded into production. First glance though shows the transformation I require is unchanged i.e.

https://maps.dubbo.nsw.gov.au/arcgis/rest/services/Utilities/Geometry/GeometryServer/findTransformations?inSR=4283&outSR=7855&extentOfInterest=&numOfResults=&vertical=false&f=html

I will follow this up further with ESRI Au to see if I have missed anything.

GDA 2020 projection and missallignment issues with GDA94 and WGS84

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