Another option would be to get the coordinates of the linking mine station and 
fixing it, and just giving that station a „perfect“ Standards deviation (isn’t 
that default if not given?)

> Am 14.11.2020 um 21:29 schrieb Ben Cooper <[email protected]>:
> 
> 
> Hi Alistair
> I would definitely link all the survey centrelines. The implication is that 
> you have some errors in the survey, but you know that the straight mine level 
> needs to be straight so the error isn’t there. One thing you could try is to 
> set the SD for the level to be very low, and the SD for the rest of the cave 
> to be quite high. When Therion distributes the error, most of this should go 
> to the survey sections either the highest SD, and the level should be less 
> distorted. 
> Best regards 
> Ben
> 
> 
> Sent from my iPhone
> 
>>> On 14 Nov 2020, at 11:49, alastair gott <[email protected]> wrote:
>>> 
>> 
>> HI Therion people,
>> 
>> I'm helping with a project we've got a cave/mine system with a really 
>> straight mine level for one of the entrances, which we have the centreline 
>> data for (but no sketches to show where the points are).
>> 
>> When the system was joined up together with all the entrances there was a 
>> kink in the mine level. so to counteract this, I removed some of the unknown 
>> survey points in the centre of the level and hung the survey on some points 
>> at the beginning and end of the level.
>> 
>> I now want to add in a section of cave in the centre of the level. I have 
>> connected this quite well in a map at a lower level with just the one 
>> entrance coordinates in it, but when I run the full map with all the 
>> entrances in, the model then tries to remove the loop error by doing it's 
>> statisical wizardry.
>> 
>> Unfortunately in doing so, it shifts the start of the level (the entrance) 
>> to the east. and then leaves the section of cave out unconnected.
>> 
>> If anyone can help, then the config for the full system is here: 
>> http://www.cave-registry.org.uk/svn/PeakDistrict/Castleton/peak_speedwell_model/
>> 
>> This is what I get:
>> 
>> <image.png>
>> 
>> 
>> the config for the one entrance coordinate is here: 
>> http://www.cave-registry.org.uk/svn/PeakDistrict/Castleton/peak_speedwell_model/speedwell_mine/Speedwell_mine_thconfig.thc
>> 
>> and these are the two selects if you want to run it at the lower level:
>> select bottomless_pit.speedwell_mine
>> select oakden_level.speedwell_mine
>> This is what I want:
>> 
>> <image.png>
>> 
>> 
>> 
>> If I add in a survey point to hook it to, then I get this:
>> <image.png>
>> 
>> 
>> Rather than this:
>> <image.png>
>> 
>> 
>> Adding in more survey points further down the passage to the south only 
>> increases the amount of distortion in a small space of passage. as there are 
>> three loop closures at the bottom of the picture [just below the red circle) 
>> which the model is running (i've just not included the maps on the drawing 
>> for clarity).
>> 
>> 
>> Regards,
>> Alastair Gott.
>> 
>> [email protected],
>> M: 07931779380.
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