[gdal-dev] Static/Dynamic datum problems

[Cameron Shorter]

Hi folks,

Our Australian spatial data users are about to face a systematic mismatch
challenge when trying to use multiple static datums (GDA2020, GDA94) with
the dynamic datum (WGS84). At the moment, it is government agencies
grappling with the problem, but it is about to become a mainstream issue.

Australia now has static datums for the years 1994 and 2020 and uses WGS84
(a time-dependent datum!), for web-mapping and web-services.  We recognise:
1. Transforming from GDA94 to GDA2020 reflects Australia’s tectonic
movement of ~ 1.8 metres to the North East.
2. GDA94 was defined as ‘equal to WGS84’ in 1994.
3. GDA2020  was defined as ‘equal to WGS84’ in 2020.
All three statements can’t be accurate. It results in mis-aligned maps in
WGS84

I believe this is a problem the whole world needs to address, given the
upcoming modernsation of significant national datums including the U.S and
we need to bring this topic into an international conversation, ASAP.
I'm interested to know if anyone here is looking into and/or has opinions
on how it should be solved. I'd like to incorporate your ideas into the
recommendations that we are putting foward.
-- 
Cameron Shorter
Technology Demystifier
Open Technologies and Geospatial Consultant

M +61 (0) 419 142 254
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