[Therion] New default settings and recent proj changes

[Bruce Mutton]

Thanks Martin

That helps a lot.  I wonder if therion.log could echo the destination folder for downloaded files?

(I could not find it on my machine)

A suggestion below.

 

therion 6.0.6+14fac78 (2022-04-26)

  - using Proj 9.0.0, compiled against 9.0.0

initialization file: C:\Program Files (x86)\Therion/therion.ini

reading ... done

configuration file: thconfig-GLMESM_System5000Map.thc

reading ... done

reading source files ... downloading the grid https://cdn.proj.org/nz_linz_nzgd2kgrid0005.tif... done

saved/cached grid file: C:\path\ nz_linz_nzgd2kgrid0005.tif

done

 

Bruce

 

From: Therion <therion-bounces at speleo.sk> On Behalf Of Martin Budaj
Sent: Wednesday, 27 April 2022 05:24
To: List for Therion users <therion at speleo.sk>
Subject: Re: [Therion] Problem with new default settings and recent proj changes

 

On Tue, Apr 26, 2022 at 11:45 AM Bruce Mutton <bruce at tomo.co.nz <mailto:bruce at tomo.co.nz> > wrote:

I am a little confused, as Therion automatically downloaded the grid and yet my therion.ini does not have any of the proj-auto or proj-missing-grid settings mentioned in the 14fac78 Therion Book pg 86-87, which raises for me many questions.  I assume the functionality of those ini statements is now superseded by the proj.ini that is now present in the install folders (as you described as "use the best transformation and download the grids if needed") and that the Therion Book is yet to be updated?

 

Indeed, thbook needs an update. Now, proj-auto is 'on' by default and proj-missing-grid is 'download'.

 

Or maybe I am not looking I the correct place for the ini files that Therion is actually using?

 

If the setting is missing in therion.ini, therion just uses the defaults. You can always override them in the therion.ini file.

  

Can Therion be run without having internet access (or without first having had internet access for a particular survey dataset at some previous time)?

 

Definitely. With the new defaults, it would attempt to download the grid (only if proj can't find it locally) and end with an error message if there is no internet connection.

 

You can do either of these:

 

* change the proj-missing-grid setting to warn, e.g. (this prints a warning stating which grid you need to download manually, then download it and put somewhere where proj finds it)

* set proj-auto off (this is the old behaviour where proj doesn't look for the optimal transformation)

* get online, run therion once, and the grids would be reused in the subsequent runs without internet connection

 

 In the attached file, do the transformations marked [no] and [yes] relate to whether they are used or not?

 

All listed transformations are used. AoU: [no] or [yes] indicates, whether proj optimised a transformation for your particular area (defined by the fixed stations in your data set) [yes] or not [no].

 

And presumably the accuracies listed are the estimated accuracies?

 

Yes, estimated by proj.

  

Can I use proj-missing-grid to improve the accuracy of my example further or is 4m accuracy the best I am likely to get for this particular dataset?

 

Sure, the accuracy when using grids should be in centimeters. It's interesting that in your log file the grid is downloaded (twice!) but not actually used by proj, it would be worth investigating why.

 

Anyway, for cases when you think you can do better than proj (including using a grid file), you can use 'cs-trans' to define a custom transformation between two coordinate systems; see an example in thbook. Probably your local GIS community has already defined such transformations; in the case of Slovakia, our cartographic office published such a list for QGIS users, which can be easily adopted for therion.

 

Martin

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