Steven

I have done this a couple of times, although I have always first created a pseudo survey by making a very (very) crude centerline based on the original plan and elevation drawings (or plan and estimated altitudes) using a scale rule and pencil.

I measure overall x and y coords of the pseudo stations (only about 10 or 20 for an entire cave) and use a spreadsheet to calculate delta x and delta y values for each pseudo leg to enter thus…

   declination 21 deg # is effective with cartesian co-ords, tick

   flags duplicate #prevents length accumulation

   flags approximate

   data cartesian from to northing easting altitude

   7  7a  90  -99  4.5

   7a 9   97 -9 4.5

   9 10   31 -22 0

I then draw a collection of scraps attached to this centerline, and THEN fix any entrances with known gps coordinates.

Ie Similar to what you have done, but there is a crude centerline that allows model outputs to be generated as well as map outputs.

Now, whenever we do some modern survey deep in the cave, there is generally a pseudo station somewhere nearby to connect to.  Of course it will be not quite in the right place, so we just add another differential pseudo leg between the closest pseudo station and the estimated position of our new modern survey.

Some related information in this link that seems closer to what you have done (but not what I have followed http://therion.speleo.sk/wiki/doku.php/faq?s[]=cartesian#how_to_add_old_lost_data_survey_to_some_new_data

Not sure if the above will be that helpful, given you have progressed as far as you have, but hopefully give you some ideas.

Bruce

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From: therion-bounces@speleo.sk [mailto:therion-bounces@speleo.sk] On Behalf Of Steven Tucker
Sent: Tuesday, 17 February 2015 7:15 p.m.
To: therion@speleo.sk
Subject: [Therion] Joining old and new surveys

Hi,

I have an old survey from the 80s and I have new sections that I want to add with Therion. The old survey has no centerline data.

I have redrawn the old survey in a th2 file and allocated 3 points which correspond to 3 different entrances. In the th file I have given coordinates to all 3 of those points. This works perfectly.

I am struggling to connect the new section with this old section. The new section starts in a deep section of the cave and is far away from any of my currently defined points.

What is the easiest way to connect the new and old sections?

Thanks,

Steven