[Therion] Problem with new default settings and recent proj changes

Tue Apr 26 11:45:10 CEST 2022

Thanks Martin

14fac78 solved both the proj download related crash and the ~100 m
positional error for lat-long and NZTM fixed points.  I have attached a cut
down version of the therion.log file that was produced.

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superseded by the proj.ini that is now present in the install folders (as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?

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

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

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

And presumably the accuracies listed are the estimated accuracies?

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?

Regards

Bruce

From: Therion <therion-bounces at speleo.sk> On Behalf Of Bruce Mutton
Sent: Monday, 25 April 2022 21:12
To: 'List for Therion users' <therion at speleo.sk>
Subject: [Therion] Problem with new default settings and recent proj changes

Martin

Something bad happened between 6.0.0 and 6.0.5 that we only just noticed
today (because for day to day work we only compile small sections of the
cave).

Therion 6.05 has moved some of our fixed stations about 100 m north (those
specified with cs lat-long and cs EPSG:2193 NZTM) and others (specified with
cs EPSG:27200 NZMG) stayed in their correct locations, severely distorting
our cave.  No errors reported, just outputs with large loop errors and
distorted cave.

Interestingly, it is the old archaic format NZMG that performs correctly and
the modern and lat-long are relocated.

The image below is located with NZMG, as is the cave entrance in the centre.
The cave entrances left and right are located with either lat-long or NZTM.

Before reporting this I thought I'd better at least try 6.0.6+3bc6556

I get a crash right away as the therion.log transcript below indicates.

therion 6.0.6+3bc6556 (2022-04-21)

  - 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... 

C:\Program Files (x86)\Therion\therion.exe: error -- couldn't download the
grid

writing xtherion file ... done

Should I be using one of the new cs-trans or proj-* commands or is there
something else?

Regards

Bruce

-----Original Message-----
From: Therion <therion-bounces at speleo.sk <mailto:therion-bounces at speleo.sk>
> On Behalf Of Martin Budaj
Sent: Friday, 22 April 2022 07:32
To: List for Therion users <therion at speleo.sk <mailto:therion at speleo.sk> >
Subject: [Therion] new default settings

Hi all,

Therion has been supporting the advanced features of the Proj library for
some time now. (Proj's purpose is to do transformations between coordinate
systems.) This functionality was disabled by default and you could enable it
using 'proj-auto' and 'proj-missing-grid' options in the initialization
file.

'proj-auto' lets Proj choose the best transformation and you can set
'proj-missing-grid' to download a grid file (see

https://proj.org/usage/transformation.html#grid-based-datum-adjustments)

if the transformation needs it; see the therion book for details. The log
file lists all the transformations chosen and used at the end.

The latest commit (3bc6556) enables this "use the best transformation and
download the grids if needed" functionality. We know that automatic
downloads are a sensitive issue, but in this case we can trust the Proj
library not to do any harm

( https://proj.org/usage/network.html ) and the user experience is much
better.

Could you check if this version works well with your data sets? The windows
installer is available here:

https://github.com/therion/therion/actions/runs/2203811478  (use the

msys2 version which uses up-to-date Proj library; you need to be logged in
to github to download it).

M.

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