by lyoyha 
, Wednesday, October 20, 2021, 07:39 (1131 days ago)
Hi Micha. It seems to me that the direction reduction does not work correctly in the program when working in the Gauss-Kruger projection. Namely, if active "horizontal distance reduction" then "direction reduction" stops working.
I am attaching a project with a triangulation network.
https://wdfiles.ru/a0668d
https://wdfiles.ru/04c32c
https://wdfiles.ru/a435ed
by Micha 
, Bad Vilbel, Wednesday, October 20, 2021, 02:33 (1131 days ago) @ lyoyha
Hello lyoyha,
I cannot download the project. However, I create a new project having Gauß-Krüger coordinates and enable both, horizontal distance reduction and direction reduction. The network was adjusted and no error occurs. The option, direction reduction, was not disabled or somethink like that. In short, I couldn't figure out what do you mean with "stop working".
Kind reagrds
Micha
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applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences
by lyoyha , Wednesday, October 20, 2021, 06:25 (1131 days ago) @ Micha
Everything is good in the first two pictures. But further, if I turn on the horizontal distance reduction, then the correction for the direction reduction is no longer applied.
Here is the project:
https://dropmefiles.com/bA1mf
Here are the pictures, if they don't load directly into my previous post:
https://dropmefiles.com/by5Ra
by Micha , Bad Vilbel, Thursday, October 21, 2021, 03:49 (1130 days ago) @ lyoyha
Hello lyoyha,
thank you for providing the project and the screenshots. I figured out the problem right now. I changed a SQL statement that adds the reduction types to the adjustment process. Can you try this JAG3D snapshot?
If it works as expected for you, I will release an official version.
Kind regards and thank you for reporting this problem!
Micha
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applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences
by lyoyha , Thursday, October 21, 2021, 07:29 (1130 days ago) @ Micha
Fine. Everything seems to work.
Now, for my example, we can say that "raw data" contains measured values on the Earth's surface (ellipsoid), and result data displays the adjusted elements already on the projection plane.
There is only one caveat: the reduction is applied specifically for directions, but not for geodetic azimuths measured on the Earth's surface. To reduce the geodetic azimuths measured on the surface of the Earth, the program needs to "be able" to calculate and apply the convergence of the meridians. In the meantime, the program does not know how to do this, it is only possible to set such a value of the geodetic azimuths measured on the surface of the Earth by a banal sequential selection so that after reduction (as in directions) we get the required azimuth value already on the projection plane.
Sorry for my English )
by Micha , Bad Vilbel, Friday, October 22, 2021, 08:14 (1129 days ago) @ lyoyha
Hello,
Fine. Everything seems to work.
Thank you for your quick reply and for confirmation.
There is only one caveat:
I don't have projects that use projections like Gauß-Krüger or UTM. That's why I don't need such reduction/correction terms during my work. In short, I'm not an expert in this area and, of course, it is not an adjustment problem. 
On the one hand, the distance reduction is very important even if the network is of small extent, on the other hand, the direction reduction is only useful, if the network extent is quite large - as far as I know. So, most adjustment applications supports the distance reduction but not the direction reduction.
Kind regards
Micha
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applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences
by Micha , Bad Vilbel, Saturday, October 23, 2021, 08:21 (1128 days ago) @ lyoyha
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applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences