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David

AUSGeoid 2020 Files

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We have been looking at the AUSGeoid 2020 files published on GA and have a few questions.

1. The uncertainties and n values are contained in separate files. This results in quite a large overhead. It seems to make more sense to have a single file containing both n values and uncertainties?

2. The links on GA are pointing to the 2017 file for the n values (https://s3-ap-southeast-2.amazonaws.com/geoid/AUSGeoid2020_20170908_win.dat) yet there is a new file from 2018 (https://s3-ap-southeast-2.amazonaws.com/geoid/AUSGeoid2020_20180201_win.dat) that appears to have been released to resolve the issue of 0.000 being used as a null value.

3. The uncertainty file has not been updated and is still using 0.000 as a null value?

 

 

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Thanks David,

Here's the response from Geoscience Australia's Geoid Team:

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Unfortunately the win.dat format doesn’t permit additional columns. If the uncertainties were added, the various software packages that, among other things, interpolate the AUSGeoid2020 files to user required latitude and longitude coordinates, would need to be updated and then they wouldn’t be backwards compatible with older geoid models.  It was safer to produce two files and avoid the additional problems associated with format changes.

Yes, you're right about the links; they will be updated. However, they shouldn’t actually make any difference for users that are using the model onshore, as the model is only valid onshore, so this shouldn’t be an issue for users.

The uncertainty offshore is set to zero so that users understand that the model is invalid offshore.

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Please let me know if you need further help.

Kind Regards
Dan

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