Declination auto vs manual

[Špela Borko]

Dear Survex users,

I have a problem using *declination auto. It seems that with "auto" command
survex consistently uses higher declination value as one can find with
online IGRF model. The error is consistent in time. I tried to use
different in and out cs. Bellow is an example with real coordinates from
where I am seeing this behaviour (13.5091 46.37474, Slovenia). Am I missing
something? Can anyone explain?

I am managing surveys for two deep caves that connected more than 1 km
below surface. Some surveys are more than 20 years old, and altogether from
more than 60 excursions, so including declination for each survey by hand
is quite painful. Since the future goals are high (more connections), I
desperately need 3d model as accurate as possible.

Thank you!

Greetings,
Špela Borko

___________________
*cs EPSG:3912
*cs out EPSG:3912
*entrance test_autodec_GK.1
*data normal from to tape compass clino
*fix test_autodec_GK.1 385675 137825 2227
*begin test_autodec_GK
*declination auto 385675 137825 2227
*date 2019.10.19
1 2 100 60 0
*end test_autodec_GK

*entrance test_nodec.1
*fix test_nodec.1 385675 137825 2227
*begin test_nodec
*date 2019.10.19
1 2 100 60 0
*end test_nodec

*entrance test_manualdec_GK.1
*fix test_manualdec_GK.1 385675 137825 2227
*begin test_manualdec_GK
*declination 3.74 degrees
*date 2019.10.19
1 2 100 60 0
*end test_manualdec_GK

*entrance test_autodec1997_GK.1
*fix test_autodec1997_GK.1 385675 137825 2227
*begin test_autodec1997_GK
*declination auto 385675 137825 2227
*date 1997
1 2 100 60 0
*end test_autodec1997_GK

*entrance test_manualdec1997_GK.1
*fix test_manualdec1997_GK.1 385675 137825 2227
*begin test_manualdec1997_GK
*declination 1.31 degrees
*date 1997
1 2 100 60 0
*end test_manualdec1997_GK

*cs LONG-LAT
*cs out EPSG:3912

*fix test_nodec_wgs.1 13.5091 46.37474  2227
*entrance test_nodec_wgs.1
*data normal from to tape compass clino ignoreall
*begin test_nodec_wgs
*date 2019.10.19
1 2 100 60 0
*end test_nodec_wgs

*declination auto 13.5091 46.37474 2227
*fix test_autodec_wgs.1 13.5091 46.37474 2227
*entrance test_autodec_wgs.1
*data normal from to tape compass clino ignoreall
*begin test_autodec_wgs
*date 2019.10.19
1 2 100 60 0
*end test_autodec_wgs