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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>Time has come to assign my least accurate survey data
a lower accuracy! <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>I’m curious as to how Therion deals with the
std deviations. Had a look, but can not find much more than is in the
Therion book.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>First, what are the default values adopted by Therion?
Currently I have only one survey in a large(ish) dataset that has been
allocated sd’s. From a casual look at the distortions it clearly
works – in that a nice result is obtained with more distortion in the
lower accuracy area. I guess that if the default values are zero, then
all the distortion would be forced to an area given non-zero sd’s; Is
this how it works?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>In this case it would seem that if one survey parameter
has a sd setting, all the surveys should all have their respective settings allocated
for this parameter to more accurately model a realistic distribution of
corrections. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>Second, has anyone made any attempt to associate sd
values with recognised cave survey grades (bcra grades for example).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>Here is my off the cuff assessment of what in NZ some
people call bcra5 but is really well short.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'> grade NZBCRA4 # Bruces assessment of the
BEST typical NZ surveying practice MIGHT achieve<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'> tape length 0.1 meter # ie -0.2m
to +0.2m for measurement to chest to 0.1m<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'> compass bearing 1 deg # ie -2 deg
to +2 deg for sighting to light of person on station to 1 deg<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'> gradient clino 1 deg # ie -2
deg to +2 deg for sighting to light of person on station and sometimes
accounting for 'eye to light' offset to 1 deg<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'> endgrade <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>I suspect the sd’s may often be larger than
this. The actual sd for polar measurements probably depends a lot on the average
length of the legs I expect<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>Thanks<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'>Bruce<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-NZ style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
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