Re: [Therion] Multiple fixes for the same point

[Martin Sluka via Therion]

OK, you are professional.

But for normal users it is better solution than only pure GPS in smart mobile, 
I think.

We compared it in forest with pro GPS and differences were not too big (in 
metres only)

Maybe if you'll test it and write here your opinion it could be useful.

Martin

On Sep 12, 2017, at 11:00 AM, Philippe Vernant via Therion  
wrote:

I will, but I’m using GPS everyday for my job, and I wouldn’t rely to much on a 
calibration of a handheld device, except if the calibration is in fact some 
kind of baseline processing on the code signal with data from a broadcasted 
nearby continuous station.

Phil



On 12 Sep 2017, at 9:34 AM, Martin Sluka via Therion  wrote:

Check that application features and check it in real situations. You’ll be 
surprised, I’m sure.

m.s.

12. 9. 2017 v 8:28, Philippe Vernant via Therion :

The problem, is that you cannot do a calibration fo a GPS since it will depend 
on the satellite constellation which change all day long even if you don’t 
move. So calibration of a GPS is a no no!
If you use accurate GPS measurements, either baseline measurement, of PPP post 
processing (but you need a GPS slightly more expensive that the regular 
handheld ;-) ) you can have an accuracy of a few millimetres. So the std-dev 
should always be given explicitly for GPS.

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Re: [Therion] Multiple fixes for the same point

[Philippe Vernant via Therion]

I will, but I’m using GPS everyday for my job, and I wouldn’t rely to much on a 
calibration of a handheld device, except if the calibration is in fact some 
kind of baseline processing on the code signal with data from a broadcasted 
nearby continuous station.

Phil



> On 12 Sep 2017, at 9:34 AM, Martin Sluka via Therion  
> wrote:
> 
> Check that application features and check it in real situations. You’ll be 
> surprised, I’m sure.
> 
> m.s.
> 
>> 12. 9. 2017 v 8:28, Philippe Vernant via Therion :
>> 
>> The problem, is that you cannot do a calibration fo a GPS since it will 
>> depend on the satellite constellation which change all day long even if you 
>> don’t move. So calibration of a GPS is a no no!
>> If you use accurate GPS measurements, either baseline measurement, of PPP 
>> post processing (but you need a GPS slightly more expensive that the regular 
>> handheld ;-) ) you can have an accuracy of a few millimetres. So the std-dev 
>> should always be given explicitly for GPS.
> 
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Re: [Therion] Multiple fixes for the same point

[Martin Sluka via Therion]

Check that application features and check it in real situations. You’ll be 
surprised, I’m sure.

m.s.

> 12. 9. 2017 v 8:28, Philippe Vernant via Therion :
> 
> The problem, is that you cannot do a calibration fo a GPS since it will 
> depend on the satellite constellation which change all day long even if you 
> don’t move. So calibration of a GPS is a no no!
> If you use accurate GPS measurements, either baseline measurement, of PPP 
> post processing (but you need a GPS slightly more expensive that the regular 
> handheld ;-) ) you can have an accuracy of a few millimetres. So the std-dev 
> should always be given explicitly for GPS.

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Re: [Therion] Multiple fixes for the same point

[Philippe Vernant via Therion]

The problem, is that you cannot do a calibration fo a GPS since it will depend 
on the satellite constellation which change all day long even if you don’t 
move. So calibration of a GPS is a no no!
If you use accurate GPS measurements, either baseline measurement, of PPP post 
processing (but you need a GPS slightly more expensive that the regular 
handheld ;-) ) you can have an accuracy of a few millimetres. So the std-dev 
should always be given explicitly for GPS.

Phil


> On 11 Sep 2017, at 21:24 PM, Martin Sluka via Therion  
> wrote:
> 
> There is an application for Android Mobile Topographer (Pro). In Pro version 
> it is 15 EUR?
> 
> It has many very interesting features to measure and use GPS including 
> calibration on known point etc.
> 
> There is only one problem with this application. It has no automatic backup 
> of measured data. So only way around is export data to an available format 
> and save it manually. Topographer crashed on my Android tablet and I loose 
> all my GPS points. On other hand the uninstallation and new installation was 
> without any problem. Just to backup a folder with exports before.
> 
> m.s.
> 
>> 11. 9. 2017 v 20:53, Xavier Pennec via Therion :
>> 
>> One of the problem for a predefined accuracy of gps measures is that it 
>> really depends on each measurement. I usually use a stddev of 2 to 3 times 
>> the figure of merit (FOM) of the GPS averaging procedure for x and y 
>> coordinates and 4 to 5 times for the altitude. This can range from a few 
>> meters (this has  to be on a plateau with no trees) to 50/100 m for 
>> measurements in forests with a few satellites only (there are also often 
>> reflections on cliffs that perturb the measure).
>> 
>> Xavier
>> 
>> Le 11-Sep-17 à 19:10, Benedikt Hallinger via Therion a écrit :
>>> No, i meant the following:
>>> 
>>> currently one has to give std-dev explicitely:
>>> fix 1.2a  0.5 0.5 0.5
>>> 
>>> it would be nice to use instead:
>>> fix 1.2a  gps
>>> where the term "gps" is some predefined accuracy, like in grade definition
>>> 
>>> 
>>> Am 2017-09-11 10:08, schrieb Bruce Mutton via Therion:
 Benedikt wrote
> The option to use "alias names" for fixes instead of directly numbers 
> would be good, this would allow to ship standards with therion and allow 
> the user to to define custom ones, just like in grade definitions.
 
 Not sure I understand correctly what you mean.
 
 We can make alias now, using equate.  This is what I usually do for gps 
 fixes.
 
 In a cave survey 'index data file'...
 centreline
 cs lat long
 fix gpsEntrance01[ etc ]
 fix gpsEntrance02   
 etc
 
 equate gpsEntrance01  53@
 equate gpsEntrance02  1@
 equate gpsEntrance01  AliasNameCreatedByThisStatement
 endcentreline
 
 ie 53@, gpsEntrance01 and AliasNameCreatedByThisStatement are all 
 alias' of each other. They all refer to the same physical point. The last 
 name is created by the equate statement, whereas the others all exist 
 prior to the execution of the equate statements.
 
 Or were you meaning something different?
 
 Bruce
 
 
 
 
 ___
 Therion mailing list
 Therion@speleo.sk
 https://mailman.speleo.sk/listinfo/therion
>>> 
>>> ___
>>> Therion mailing list
>>> Therion@speleo.sk
>>> https://mailman.speleo.sk/listinfo/therion
>> 
>> -- 
>>> -
>>> Xavier Pennec
>>> Senior Research Scientist / Directeur de recherche
>>> Asclepios project-team, INRIA Sophia-Antipolis
>>> 2004 Route des Lucioles, BP93
>>> F-06902 Sophia-Antipolis Cedex, France
>>> +33 4 92 38 76 64
>>> +33 6 78 35 16 90
>>> http://www-sop.inria.fr/asclepios/
>>> ---
>> 
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Re: [Therion] Multiple fixes for the same point

[Martin Sluka via Therion]

There is an application for Android Mobile Topographer (Pro). In Pro version it 
is 15 EUR?

It has many very interesting features to measure and use GPS including 
calibration on known point etc.

There is only one problem with this application. It has no automatic backup of 
measured data. So only way around is export data to an available format and 
save it manually. Topographer crashed on my Android tablet and I loose all my 
GPS points. On other hand the uninstallation and new installation was without 
any problem. Just to backup a folder with exports before.

m.s.

> 11. 9. 2017 v 20:53, Xavier Pennec via Therion :
> 
> One of the problem for a predefined accuracy of gps measures is that it 
> really depends on each measurement. I usually use a stddev of 2 to 3 times 
> the figure of merit (FOM) of the GPS averaging procedure for x and y 
> coordinates and 4 to 5 times for the altitude. This can range from a few 
> meters (this has  to be on a plateau with no trees) to 50/100 m for 
> measurements in forests with a few satellites only (there are also often 
> reflections on cliffs that perturb the measure).
> 
> Xavier
> 
> Le 11-Sep-17 à 19:10, Benedikt Hallinger via Therion a écrit :
>> No, i meant the following:
>> 
>> currently one has to give std-dev explicitely:
>> fix 1.2a  0.5 0.5 0.5
>> 
>> it would be nice to use instead:
>> fix 1.2a  gps
>> where the term "gps" is some predefined accuracy, like in grade definition
>> 
>> 
>> Am 2017-09-11 10:08, schrieb Bruce Mutton via Therion:
>>> Benedikt wrote
 The option to use "alias names" for fixes instead of directly numbers 
 would be good, this would allow to ship standards with therion and allow 
 the user to to define custom ones, just like in grade definitions.
>>> 
>>> Not sure I understand correctly what you mean.
>>> 
>>> We can make alias now, using equate.  This is what I usually do for gps 
>>> fixes.
>>> 
>>> In a cave survey 'index data file'...
>>> centreline
>>> cs lat long
>>> fix gpsEntrance01[ etc ]
>>> fix gpsEntrance02   
>>> etc
>>> 
>>> equate gpsEntrance01  53@
>>> equate gpsEntrance02  1@
>>> equate gpsEntrance01  AliasNameCreatedByThisStatement
>>> endcentreline
>>> 
>>> ie 53@, gpsEntrance01 and AliasNameCreatedByThisStatement are all 
>>> alias' of each other. They all refer to the same physical point. The last 
>>> name is created by the equate statement, whereas the others all exist prior 
>>> to the execution of the equate statements.
>>> 
>>> Or were you meaning something different?
>>> 
>>> Bruce
>>> 
>>> 
>>> 
>>> 
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>>> https://mailman.speleo.sk/listinfo/therion
>> 
>> ___
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> 
> -- 
>> -
>> Xavier Pennec
>> Senior Research Scientist / Directeur de recherche
>> Asclepios project-team, INRIA Sophia-Antipolis
>> 2004 Route des Lucioles, BP93
>> F-06902 Sophia-Antipolis Cedex, France
>> +33 4 92 38 76 64
>> +33 6 78 35 16 90
>> http://www-sop.inria.fr/asclepios/
>> ---
> 
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Re: [Therion] Multiple fixes for the same point

[Xavier Pennec via Therion]

One of the problem for a predefined accuracy of gps measures is that it 
really depends on each measurement. I usually use a stddev of 2 to 3 
times the figure of merit (FOM) of the GPS averaging procedure for x and 
y coordinates and 4 to 5 times for the altitude. This can range from a 
few meters (this has  to be on a plateau with no trees) to 50/100 m for 
measurements in forests with a few satellites only (there are also often 
reflections on cliffs that perturb the measure).


Xavier

Le 11-Sep-17 à 19:10, Benedikt Hallinger via Therion a écrit :

No, i meant the following:

currently one has to give std-dev explicitely:
 fix 1.2a  0.5 0.5 0.5

it would be nice to use instead:
 fix 1.2a  gps
where the term "gps" is some predefined accuracy, like in grade 
definition



Am 2017-09-11 10:08, schrieb Bruce Mutton via Therion:

Benedikt wrote
The option to use "alias names" for fixes instead of directly 
numbers would be good, this would allow to ship standards with 
therion and allow the user to to define custom ones, just like in 
grade definitions.


Not sure I understand correctly what you mean.

We can make alias now, using equate.  This is what I usually do for 
gps fixes.


In a cave survey 'index data file'...
centreline
cs lat long
fix gpsEntrance01[ etc ]
fix gpsEntrance02   
etc

equate gpsEntrance01  53@
equate gpsEntrance02  1@
equate gpsEntrance01  AliasNameCreatedByThisStatement
endcentreline

ie 53@, gpsEntrance01 and AliasNameCreatedByThisStatement 
are all alias' of each other. They all refer to the same physical 
point. The last name is created by the equate statement, whereas the 
others all exist prior to the execution of the equate statements.


Or were you meaning something different?

Bruce




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--

-
Xavier Pennec
Senior Research Scientist / Directeur de recherche
Asclepios project-team, INRIA Sophia-Antipolis
2004 Route des Lucioles, BP93
F-06902 Sophia-Antipolis Cedex, France
+33 4 92 38 76 64
+33 6 78 35 16 90
http://www-sop.inria.fr/asclepios/
---


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Re: [Therion] Multiple fixes for the same point

[Benedikt Hallinger via Therion]

No, i meant the following:

currently one has to give std-dev explicitely:
 fix 1.2a  0.5 0.5 0.5

it would be nice to use instead:
 fix 1.2a  gps
where the term "gps" is some predefined accuracy, like in grade definition


Am 2017-09-11 10:08, schrieb Bruce Mutton via Therion:

Benedikt wrote
The option to use "alias names" for fixes instead of directly numbers 
would be good, this would allow to ship standards with therion and allow 
the user to to define custom ones, just like in grade definitions.


Not sure I understand correctly what you mean.

We can make alias now, using equate.  This is what I usually do for gps 
fixes.


In a cave survey 'index data file'...
centreline
cs lat long
fix gpsEntrance01[ etc ]
fix gpsEntrance02   
etc

equate gpsEntrance01  53@
equate gpsEntrance02  1@
equate gpsEntrance01  AliasNameCreatedByThisStatement
endcentreline

ie 53@, gpsEntrance01 and AliasNameCreatedByThisStatement are all 
alias' of each other.  They all refer to the same physical point. The last 
name is created by the equate statement, whereas the others all exist prior 
to the execution of the equate statements.


Or were you meaning something different?

Bruce




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Re: [Therion] Multiple fixes for the same point

[Bruce Mutton via Therion]

Benedikt wrote
>The option to use "alias names" for fixes instead of directly numbers would be 
>good, this would allow to ship standards with therion and allow the user to to 
>define custom ones, just like in grade definitions.

Not sure I understand correctly what you mean.

We can make alias now, using equate.  This is what I usually do for gps fixes.

In a cave survey 'index data file'...
centreline
cs lat long
fix gpsEntrance01[ etc ]
fix gpsEntrance02   
etc

equate gpsEntrance01  53@
equate gpsEntrance02  1@
equate gpsEntrance01  AliasNameCreatedByThisStatement
endcentreline

ie 53@, gpsEntrance01 and AliasNameCreatedByThisStatement are all 
alias' of each other.  They all refer to the same physical point. The last name 
is created by the equate statement, whereas the others all exist prior to the 
execution of the equate statements.

Or were you meaning something different?

Bruce




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Re: [Therion] Multiple fixes for the same point

[Benedikt Hallinger via Therion]

The option to use "alias names" for fixes instead of directly numbers would 
be good, this would allow to ship standards with therion and allow the user 
to to define custom ones, just like in grade definitions.


Why not extend the grades definition to allow specification of fix std 
deviation there?
Btw, I would expect therion to not make assumptions on the fix accuracy 
unless i state it to do so (dont change status quo).


Am 2017-09-10 0:54, schrieb Andrew Atkinson via Therion:

Bruce

Okay I can see your logic, but Im not sure I agree. However, the following 
is a thought dump, which may not be my final position and partly might just 
be to argue to check your rohbustness, but hope it helps us all in 
understanding.


First Therion throws an warning not an error for a multiple fix with no 
variance, I think this is a big, taking only one result is not useful or 
intuitive. Maybe the ultimate answer is Therion to throw an error. (I have 
lots of warnings so dont always notice a new one)


That said, a variance is set to other readings, which can be changed, why 
treat fix as different. There has never been an exact fix. And yes I can see 
the arguement for keeping the status quo, but feel there is a strong 
arguement for changing it to a default no zero variance, as I think most 
people believe that is what is happening ( yes we should all read the survex 
manual in more detail, but often we do not.) Now I do think there is an 
agreement to have whether a variance for read off map or GPS should be set, 
but maybe some predictive ones a bit like the survey grades is the way to 
go.


Anyway, I doubt anything will happen, explicitly defining variances will 
solve the problem and the programmers have more important things to work on, 
but it has been interesting debate and certainly got my head find it


Thanks

Andrew

On 9 Sep 2017 10:35 pm, "Bruce Mutton via Therion"  
wrote:



Survex manual https://survex.com/docs/manual/datafile.htm [1]

FIX fixes the position of  at the given coordinates. … THE 
STANDARD ERRORS DEFAULT TO ZERO (FIX STATION EXACTLY).  CAVERN WILL GIVE AN 
ERROR IF YOU ATTEMPT TO FIX THE SAME SURVEY STATION TWICE AT DIFFERENT 
COORDINATES, or a warning if you fix it twice with matching coordinates.


Further reading about fix and cs in the survex manual explains some 
reasoning and how you can use the implemented behaviour to best effect.


 

Therion manual

FIX  [   [  ]]  fix station 
coordinates (with specified errors—only the units transformation, not 
calibration, is applied to them).


 

* As a beginner, years ago, I took it as self-evident (after reading only 
the Therion manual) that omitting standard errors was tantamount to the 
user telling the software, ‘I want you to fix this position with no 
corrections or adjustments’.  I expect this would be the usual assumption, 
 for a non-technical user, and the easiest input arrangement.  They should 
expect an error if they accidentally apply two fixes to the same station.  
This means all the distortion due to loop closure occurs in survey legs.  
And it means that a user can be confident that they more or less have 
control over what the software is doing.


 

* The next step is to realise that applying standard errors to fixed 
stations allows the distortion to be shared between the survey leg network 
and the fixed stations.  That means fixes for positions of your cave with 
at least two entrances (and at least 2 fixed stations) can self-adjust to 
what is perhaps some sort of best fit.


 

* For users who want to add another level of complication, as I 
eventually did, the concept of applying multiple coordinates to a single 
fixed station can be used.  Requiring standard errors to be defined 
explicitly case by case protects newer users from what would usually be 
unintentional duplication.  There are tricks to getting this to work in 
Therion, as the old forum posts I linked to allude to.  (I am not even sure 
if they are working in my projects, as I have not focused on those areas 
for a few years – perhaps I should have another look!)


 

My vote is squarely with the status quo (with any bugs that may remain in 
step 3 repaired, of course).


Bruce

 

-Original Message-
From: Therion [mailto:therion-boun...@speleo.sk [2]] On Behalf Of Andrew 
Atkinson via Therion

On 08/09/17 20:47, Bruce Mutton via Therion wrote:

As above, I think Therion already provides users with straight forward 
control.  Aside from a few quirks and maybe bugs of course.


 

Yep Im sure this is a quirk, maybe even a bug. The default of no variance 
means that multiple entrance co-ordinates cannot be entered in the most 
obvious manor, as currently Therion will only take one of them.


There is a way round it, that takes experience, it would be better if the 
most obvious way of entering it, did what you might assume, which is what I 
and probably others, especially beginners did/do.


 

thanks

 

Andrew

 
__

Re: [Therion] Multiple fixes for the same point

[Andrew Atkinson via Therion]

Bruce

Okay I can see your logic, but I'm not sure I agree. However, the following
is a thought dump, which may not be my final position and partly might just
be to argue to check your rohbustness, but hope it helps us all in
understanding.

First Therion throws an warning not an error for a multiple fix with no
variance, I think this is a big, taking only one result is not useful or
intuitive. Maybe the ultimate answer is Therion to throw an error. (I have
lots of warnings so don't always notice a new one)

That said, a variance is set to other readings, which can be changed, why
treat fix as different. There has never been an exact fix. And yes I can
see the arguement for keeping the status quo, but feel there is a strong
arguement for changing it to a default no zero variance, as I think most
people believe that is what is happening ( yes we should all read the
survex manual in more detail, but often we do not.) Now I do think there is
an agreement to have whether a variance for read off map or GPS should be
set, but maybe some predictive ones a bit like the survey grades is the way
to go.

Anyway, I doubt anything will happen, explicitly defining variances will
solve the problem and the programmers have more important things to work
on, but it has been interesting debate and certainly got my head find it

Thanks

Andrew

On 9 Sep 2017 10:35 pm, "Bruce Mutton via Therion" 
wrote:

> Survex manual https://survex.com/docs/manual/datafile.htm
>
> *fix* fixes the position of  at the given coordinates. … *The
> standard errors default to zero (fix station exactly).*  *Cavern will
> give an error if you attempt to fix the same survey station twice at
> different coordinates*, or a warning if you fix it twice with matching
> coordinates.
>
> Further reading about fix and cs in the survex manual explains some
> reasoning and how you can use the implemented behaviour to best effect.
>
>
>
> Therion manual
>
> *fix*  [   [  ]]  fix station
> coordinates (with specified errors—only the units transformation, not
> calibration, is applied to them).
>
>
>
>1. As a beginner, years ago, I took it as self-evident (after reading
>only the Therion manual) that omitting standard errors was tantamount to
>the user telling the software, ‘I want you to fix this position with no
>corrections or adjustments’.  I expect this would be the usual assumption,
> for a non-technical user, and the easiest input arrangement.  They should
>expect an error if they accidentally apply two fixes to the same station.
>This means all the distortion due to loop closure occurs in survey legs.
>And it means that a user can be confident that they more or less have
>control over what the software is doing.
>
>
>
>1. The next step is to realise that applying standard errors to fixed
>stations allows the distortion to be shared between the survey leg network
>and the fixed stations.  That means fixes for positions of your cave with
>at least two entrances (and at least 2 fixed stations) can self-adjust to
>what is perhaps some sort of best fit.
>
>
>
>1. For users who want to add another level of complication, as I
>eventually did, the concept of applying multiple coordinates to a single
>fixed station can be used.  Requiring standard errors to be defined
>explicitly case by case protects newer users from what would usually be
>unintentional duplication.  There are tricks to getting this to work in
>Therion, as the old forum posts I linked to allude to.  (I am not even sure
>if they are working in my projects, as I have not focused on those areas
>for a few years – perhaps I should have another look!)
>
>
>
> My vote is squarely with the status quo (with any bugs that may remain in
> step 3 repaired, of course).
>
> Bruce
>
>
>
> -Original Message-
> From: Therion [mailto:therion-boun...@speleo.sk] On Behalf Of Andrew
> Atkinson via Therion
> On 08/09/17 20:47, Bruce Mutton via Therion wrote:
>
> > As above, I think Therion already provides users with straight forward
> control.  Aside from a few quirks and maybe bugs of course.
>
>
>
> Yep I'm sure this is a quirk, maybe even a bug. The default of no variance
> means that multiple entrance co-ordinates cannot be entered in the most
> obvious manor, as currently Therion will only take one of them.
>
> There is a way round it, that takes experience, it would be better if the
> most obvious way of entering it, did what you might assume, which is what I
> and probably others, especially beginners did/do.
>
>
>
> thanks
>
>
>
> Andrew
>
>
>
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Re: [Therion] Multiple fixes for the same point

[Bruce Mutton via Therion]

Survex manual https://survex.com/docs/manual/datafile.htm 

fix fixes the position of  at the given coordinates. … The standard 
errors default to zero (fix station exactly).  Cavern will give an error if you 
attempt to fix the same survey station twice at different coordinates, or a 
warning if you fix it twice with matching coordinates.

Further reading about fix and cs in the survex manual explains some reasoning 
and how you can use the implemented behaviour to best effect.

 

Therion manual

fix  [   [  ]]  fix station coordinates 
(with specified errors—only the units transformation, not calibration, is 
applied to them).

 

1.  As a beginner, years ago, I took it as self-evident (after reading only 
the Therion manual) that omitting standard errors was tantamount to the user 
telling the software, ‘I want you to fix this position with no corrections or 
adjustments’.  I expect this would be the usual assumption,  for a 
non-technical user, and the easiest input arrangement.  They should expect an 
error if they accidentally apply two fixes to the same station.  This means all 
the distortion due to loop closure occurs in survey legs.  And it means that a 
user can be confident that they more or less have control over what the 
software is doing.

 

2.  The next step is to realise that applying standard errors to fixed 
stations allows the distortion to be shared between the survey leg network and 
the fixed stations.  That means fixes for positions of your cave with at least 
two entrances (and at least 2 fixed stations) can self-adjust to what is 
perhaps some sort of best fit. 

 

3.  For users who want to add another level of complication, as I 
eventually did, the concept of applying multiple coordinates to a single fixed 
station can be used.  Requiring standard errors to be defined explicitly case 
by case protects newer users from what would usually be unintentional 
duplication.  There are tricks to getting this to work in Therion, as the old 
forum posts I linked to allude to.  (I am not even sure if they are working in 
my projects, as I have not focused on those areas for a few years – perhaps I 
should have another look!)

 

My vote is squarely with the status quo (with any bugs that may remain in step 
3 repaired, of course).

Bruce

 

-Original Message-
From: Therion [mailto:therion-boun...@speleo.sk] On Behalf Of Andrew Atkinson 
via Therion
On 08/09/17 20:47, Bruce Mutton via Therion wrote:

> As above, I think Therion already provides users with straight forward 
> control.  Aside from a few quirks and maybe bugs of course.

 

Yep I'm sure this is a quirk, maybe even a bug. The default of no variance 
means that multiple entrance co-ordinates cannot be entered in the most obvious 
manor, as currently Therion will only take one of them.

There is a way round it, that takes experience, it would be better if the most 
obvious way of entering it, did what you might assume, which is what I and 
probably others, especially beginners did/do.

 

thanks

 

Andrew

 

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Re: [Therion] Multiple fixes for the same point

[Graham Mullan via Therion]

Andrew has shown up an interesting flaw in both Therion and Survex. A single 
fix of a point, unless otherwise qualified, will always be presumed to be more 
accurate than multiple fixes than multiple fixes even though (I suppose, I 
don't have the maths) the latter should be better. Unless one is using a decent 
dGPS system to fix the points, it is also potentially the case that the 
relationship between two fixed points at entrances will be better described by 
the intervening underground survey data than by the GPS fixes made using 
consumer hand-held devices.

I will soon have to be dealing with a similar problem with a multi-entrance 
cave as the various lines of data join up - like Andrew's this is a dataset 
obtained on expo and I'll not get any more data until next year so 'soon' is a 
bit wrong. I think we will solve this by getting as good a fix as possible for 
one entrance and then using our survey data to delimit the other entrances. 
I'll also, however collect GPS records of the same spots and highlight the 
differences.

The answer may be to insist that fixed point data must include an estimate of 
precision and that non-entry for that field would default to something worse 
than an exact fix.

I have, in the past done this the other way around, though. I have a dataset 
for one relatively linear multi-entrance cave, but the data is very old and was 
not collected using an inclinometer, passage gradients are generally of the 
order of 2-3 degrees. So I used the fixed points for the entrances to skew the 
profile of the cave. The resulting model was a reasonable facsimile of reality.

Graham

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Re: [Therion] Multiple fixes for the same point

[Andrew Atkinson via Therion]

On 08/09/17 20:47, Bruce Mutton via Therion wrote:
> As above, I think Therion already provides users with straight forward 
> control.  Aside from a few quirks and maybe bugs of course.

Yep I'm sure this is a quirk, maybe even a bug. The default of no
variance means that multiple entrance co-ordinates cannot be entered in
the most obvious manor, as currently Therion will only take one of them.
There is a way round it, that takes experience, it would be better if
the most obvious way of entering it, did what you might assume, which is
what I and probably others, especially beginners did/do.

thanks

Andrew
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Re: [Therion] Multiple fixes for the same point

[Bruce Mutton via Therion]

From Andrews post

>Now one of the answers which I might start to do is always be explicit in the 
>variance, however, is it really reasonable for survex and therefore therion to 
>assume a fix is perfect, we know that they are not. 

That is the right approach I think Andrew.  I have always omitted variance when 
I want Therion to assume a fix is perfect (knowing of course it is not quite 
perfect) and included a variance on EVERY fixed point I want therion to adjust 
in the same way it adjusts survey legs.  The variance is analogous to survey 
grade or sd, and so we tweak each in every survey according to the perceived 
quality of each component (if we want to, otherwise just ignore it).

> gps locations fixed by survey legs all the error is distributed to the survey 
> legs, does not seem right.
So what I'm suggesting is that the default for fix to be perfect should be 
looked at and maybe amended to almost perfect variance.

As above, I think Therion already provides users with straight forward control. 
 Aside from a few quirks and maybe bugs of course.
Guidance on typical fixed point variances for common devices and coordinate 
sources would not go amiss however.

Bruce


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Re: [Therion] Multiple fixes for the same point

[Wookey via Therion]

On 2017-09-07 14:46 +0100, Andrew Atkinson via Therion wrote:
> On 07/09/17 14:23, Wookey via Therion wrote:
> > I've wanted to do this too, but wasn't sure how.
> > 
> > Alternatively you can give them different names (with variances), then 
> > equate them.
> 
> Okay that probably will get round it, but is that the right solution? As
> this entrance has 3 locations it gets a variance, but most of the other
> 9 entrances only have one fix. This would mean they are deemed perfectly
> correct, while the ones with more than one location will be moved by the
> averaging and the surveys that connects all the entrances together. So
> in this case I could just go through and give a the variances for all
> the fixes in the data files (it is only a small set.) However it is part
> of a very large data set, with something like 200 entrances, that will
> take me sometime (or a script.) Now one of the answers which I might
> start to do is always be explicit in the variance, however, is it really
> reasonable for survex and therefore therion to assume a fix is perfect,
> we know that they are not.

No. Almost all fixed points really have some sort of variance. Having
standard 'GPS' assumptions for GPS points would be helpful. We really
should be putting some numbers in for this until Survex/Therion does
it for us.

Fixed points coming off map benchmarks or laser surveys could have
very small variances which might be close enough to zero that leaving
them as zero is not too innacurate.

> 2 gps locations fixed by survey legs all the
> error is distributed to the survey legs, does not seem right.
> So what I'm suggesting is that the default for fix to be perfect should
> be looked at and maybe amended to almost perfect variance.

Agreed, or at least some shorthand for 'type of fix'. 

Wookey
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Re: [Therion] Multiple fixes for the same point

[Philippe Vernant via Therion]

Andrew,

GPS coordinates should come with uncertainties. If nothing went wrong when you 
took the coordinates, they should all be within their uncertainties. They could 
all be very close from each others but still be off the exact coordinates (that 
is the difference between accuracy and repeatability). If all the coordinates 
of the entrances were taken with GPS, I would rather use these coordinates and 
their uncertainties in the processing and pick one of the three sets of 
coordinates for the surface point. This will be way more accurate that just 
trying to do some kind of covariance on the three sets of coordinates to make 
it look more accurate, but which in fact won’t really matter. If you 
coordinates where taken with handheld GPS, your cave survey for the 9 entrances 
should be more accurate than the GPS coordinates.

Phil


> On 07 Sep 2017, at 14:07 PM, Andrew Atkinson via Therion  
> wrote:
> 
> I'm sure that this has been covered, but I cannot find it anywhere.
> 
> I have 3 different gps results for a surface point, all taken with the
> same gps but on different days, so rather then picking one I just used
> fix on all 3.
> 
> However, therion appears to be taking only the last one I enter.
> This does not seem to be the right behaviour! Is there a way for Therion
> to take all 3 and 'average' them?
> 
> thanks in advance
> 
> Andrew
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Re: [Therion] Multiple fixes for the same point

[Xavier Pennec via Therion]

Hi Bruce,

Good that you found my previous post. I knew I wrote something on it but 
I could not remember when.
I also remenber that the therion loop closure algorithm was inducing 
(sometimes) very large errors while the survex loop closure was working 
perfectly. I am not sure that it was for this case, but I am personnaly 
taking care of installing survex for loop closure: the last experience I 
had without survex installed last November was still showing the problem 
(coordinates too large to be able to produce the pdf).


Xavier

Le 07-Sep-17 à 21:42, Bruce Mutton via Therion a écrit :

Andrew
I have been doing this for years, and pretty sure it is working fine, no errors 
or warnings flagged by Therion at least.  Although I have not checked that the 
weighted averaging of the positions appears to be working correctly for about 5 
years now, so there is a possibility it has got broken in the meantime. However 
nothing gross is happening or I would have noticed.
There were some issues and work arounds that were discussed on the forum.
https://www.mail-archive.com/therion@speleo.sk/msg03747.html Olly on Survex Jan 
2012
https://www.mail-archive.com/therion@speleo.sk/msg03750.html Describing the 
characteristics
https://www.mail-archive.com/therion@speleo.sk/msg03751.html Stacho looking 
into it
https://www.mail-archive.com/therion@speleo.sk/msg04327.html  Xaviers solution 
Dec 2013

I vaguely recall that the multiple fixes did start turning up in loop 
reporting, as Satcho described, but I'm not sure about that - could be 
imagination.

I think it is appropriate functionality for Therion.  Over time many position 
fixes on a station, usually in different surveys, all with their own std 
errors.  Therion as far as I know handles these just fine, averaging 
appropriately.  If it does not, then something is broken.

At least two datasets where I do this are still in active use, if I get time I 
will make sure all is still well.

I think it is a topic that deserves a wiki FAQ or Tips and Tricks entry

Bruce

-Original Message-
From: Therion [mailto:therion-boun...@speleo.sk] On Behalf Of Andrew Atkinson 
via Therion
Sent: Friday, 8 September 2017 12:08 AM
To: List for Therion users 
Cc: Andrew Atkinson 
Subject: [Therion] Multiple fixes for the same point

I'm sure that this has been covered, but I cannot find it anywhere.

I have 3 different gps results for a surface point, all taken with the same gps 
but on different days, so rather then picking one I just used fix on all 3.

However, therion appears to be taking only the last one I enter.
This does not seem to be the right behaviour! Is there a way for Therion to 
take all 3 and 'average' them?

thanks in advance

Andrew
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--

-
Xavier Pennec
Senior Research Scientist / Directeur de recherche
Asclepios project-team, INRIA Sophia-Antipolis
2004 Route des Lucioles, BP93
F-06902 Sophia-Antipolis Cedex, France
+33 4 92 38 76 64
+33 6 78 35 16 90
http://www-sop.inria.fr/asclepios/
---


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Re: [Therion] Multiple fixes for the same point

[Bruce Mutton via Therion]

Andrew
I have been doing this for years, and pretty sure it is working fine, no errors 
or warnings flagged by Therion at least.  Although I have not checked that the 
weighted averaging of the positions appears to be working correctly for about 5 
years now, so there is a possibility it has got broken in the meantime. However 
nothing gross is happening or I would have noticed.
There were some issues and work arounds that were discussed on the forum.
https://www.mail-archive.com/therion@speleo.sk/msg03747.html Olly on Survex Jan 
2012
https://www.mail-archive.com/therion@speleo.sk/msg03750.html Describing the 
characteristics
https://www.mail-archive.com/therion@speleo.sk/msg03751.html Stacho looking 
into it
https://www.mail-archive.com/therion@speleo.sk/msg04327.html  Xaviers solution 
Dec 2013

I vaguely recall that the multiple fixes did start turning up in loop 
reporting, as Satcho described, but I'm not sure about that - could be 
imagination.

I think it is appropriate functionality for Therion.  Over time many position 
fixes on a station, usually in different surveys, all with their own std 
errors.  Therion as far as I know handles these just fine, averaging 
appropriately.  If it does not, then something is broken.

At least two datasets where I do this are still in active use, if I get time I 
will make sure all is still well.

I think it is a topic that deserves a wiki FAQ or Tips and Tricks entry

Bruce

-Original Message-
From: Therion [mailto:therion-boun...@speleo.sk] On Behalf Of Andrew Atkinson 
via Therion
Sent: Friday, 8 September 2017 12:08 AM
To: List for Therion users 
Cc: Andrew Atkinson 
Subject: [Therion] Multiple fixes for the same point

I'm sure that this has been covered, but I cannot find it anywhere.

I have 3 different gps results for a surface point, all taken with the same gps 
but on different days, so rather then picking one I just used fix on all 3.

However, therion appears to be taking only the last one I enter.
This does not seem to be the right behaviour! Is there a way for Therion to 
take all 3 and 'average' them?

thanks in advance

Andrew
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Re: [Therion] Multiple fixes for the same point

[Andrew Atkinson via Therion]

On 07/09/17 14:23, Wookey via Therion wrote:
> I've wanted to do this too, but wasn't sure how.
> 
> From *FIX on https://survex.com/docs/manual/datafile.htm
> 
>  The standard errors default to zero (fix station exactly). cavern
>  will give an error if you attempt to fix the same survey station
>  twice at different coordinates, or a warning if you fix it twice with
>  matching coordinates.

Hmm therion has an error message from survex

 3> /tmp/th5506/data.svx:27: error: Station already fixed or equated to
a fixed point
 4>  *fix   14  57300.0052840.00240.00
 5> /tmp/th5506/data.svx:28: error: Station already fixed or equated to
a fixed point
 6>  *fix   14  57302.0052844.00240.00 but

processes it any way
> 
>  You can also specify just one standard error (in which case it is
>  assumed equal in X, Y, and Z) or two (in which case the first is
>  taken as the standard error in X and Y, and the second as the
>  standard error in Z).
> 
> So I just checked and if you add some variances you can then give more than 
> one set of locations for it without getting errors, and the final location is 
> the average.
> 
> Alternatively you can give them different names (with variances), then equate 
> them.
> 
> So survex can do the right thing. Hopefully therion will pass this
> through so that it works right, but I've not tested that.
> 
> So this works:
> *fix pt1 5 5 5   1 1 1
> *fix pt1 5 5.5 5 1 1 1
> 
> dump3d fixtest.3d:
> ERROR_INFO #legs 2, len 0.00m, E 0.20 H 0.25 V 0.00
> NODE 5.00 5.25 5.00 [pt1] FIXED
> 
> And so does this:
> *fix pt1_1 5 5 5   1 1 1
> *fix pt1_2 5 5.5 5 1 1 1
> *equate pt1_1 pt1_2
> 
> dump3d fixtest.3d:
> ERROR_INFO #legs 2, len 0.00m, E 0.20 H 0.25 V 0.00
> NODE 5.00 5.25 5.00 [pt1_1] FIXED
> NODE 5.00 5.25 5.00 [pt1_2] FIXED

Okay that probably will get round it, but is that the right solution? As
this entrance has 3 locations it gets a variance, but most of the other
9 entrances only have one fix. This would mean they are deemed perfectly
correct, while the ones with more than one location will be moved by the
averaging and the surveys that connects all the entrances together. So
in this case I could just go through and give a the variances for all
the fixes in the data files (it is only a small set.) However it is part
of a very large data set, with something like 200 entrances, that will
take me sometime (or a script.) Now one of the answers which I might
start to do is always be explicit in the variance, however, is it really
reasonable for survex and therefore therion to assume a fix is perfect,
we know that they are not. 2 gps locations fixed by survey legs all the
error is distributed to the survey legs, does not seem right.
So what I'm suggesting is that the default for fix to be perfect should
be looked at and maybe amended to almost perfect variance.

thanks

Andrew
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Re: [Therion] Multiple fixes for the same point

[Wookey via Therion]

On 2017-09-07 13:07 +0100, Andrew Atkinson via Therion wrote:
> I'm sure that this has been covered, but I cannot find it anywhere.
> 
> I have 3 different gps results for a surface point, all taken with the
> same gps but on different days, so rather then picking one I just used
> fix on all 3.
> 
> However, therion appears to be taking only the last one I enter.
> This does not seem to be the right behaviour! Is there a way for Therion
> to take all 3 and 'average' them?

I've wanted to do this too, but wasn't sure how.

From *FIX on https://survex.com/docs/manual/datafile.htm

 The standard errors default to zero (fix station exactly). cavern
 will give an error if you attempt to fix the same survey station
 twice at different coordinates, or a warning if you fix it twice with
 matching coordinates.

 You can also specify just one standard error (in which case it is
 assumed equal in X, Y, and Z) or two (in which case the first is
 taken as the standard error in X and Y, and the second as the
 standard error in Z).

So I just checked and if you add some variances you can then give more than one 
set of locations for it without getting errors, and the final location is the 
average.

Alternatively you can give them different names (with variances), then equate 
them.

So survex can do the right thing. Hopefully therion will pass this
through so that it works right, but I've not tested that.

So this works:
*fix pt1 5 5 5   1 1 1
*fix pt1 5 5.5 5 1 1 1

dump3d fixtest.3d:
ERROR_INFO #legs 2, len 0.00m, E 0.20 H 0.25 V 0.00
NODE 5.00 5.25 5.00 [pt1] FIXED

And so does this:
*fix pt1_1 5 5 5   1 1 1
*fix pt1_2 5 5.5 5 1 1 1
*equate pt1_1 pt1_2

dump3d fixtest.3d:
ERROR_INFO #legs 2, len 0.00m, E 0.20 H 0.25 V 0.00
NODE 5.00 5.25 5.00 [pt1_1] FIXED
NODE 5.00 5.25 5.00 [pt1_2] FIXED


Wookey
-- 
Principal hats:  Linaro, Debian, Wookware, ARM
http://wookware.org/


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Re: [Therion] Multiple fixes for the same point

[Martin Sluka via Therion]

Way to coerce Therion to to substitute GPS software?

m.s.

On Sep 07, 2017, at 03:01 PM, Andrew Atkinson via Therion  
wrote:

Yes I could do that, but it does not feel very elegant, and not really
the way you should do it, it would be the equivalent of reversing all
backwards legs and adding the original as a comment

Andrew

On 07/09/17 13:46, Martin Sluka via Therion wrote:

To average it before (in GPS software) and to add all three as comment?

m.s.


On Sep 07, 2017, at 02:08 PM, Andrew Atkinson via Therion
 wrote:

I'm sure that this has been covered, but I cannot find it anywhere.

I have 3 different gps results for a surface point, all taken with the
same gps but on different days, so rather then picking one I just used
fix on all 3.

However, therion appears to be taking only the last one I enter.
This does not seem to be the right behaviour! Is there a way for Therion
to take all 3 and 'average' them?

thanks in advance

Andrew
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Re: [Therion] Multiple fixes for the same point

[Andrew Atkinson via Therion]

Yes I could do that, but it does not feel very elegant, and not really
the way you should do it, it would be the equivalent of reversing all
backwards legs and adding the original as a comment

Andrew

On 07/09/17 13:46, Martin Sluka via Therion wrote:
> 
> To average it before (in GPS software) and to add all three as comment?
> 
> m.s.
> 
> 
> On Sep 07, 2017, at 02:08 PM, Andrew Atkinson via Therion
>  wrote:
> 
>> I'm sure that this has been covered, but I cannot find it anywhere.
>>
>> I have 3 different gps results for a surface point, all taken with the
>> same gps but on different days, so rather then picking one I just used
>> fix on all 3.
>>
>> However, therion appears to be taking only the last one I enter.
>> This does not seem to be the right behaviour! Is there a way for Therion
>> to take all 3 and 'average' them?
>>
>> thanks in advance
>>
>> Andrew
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Re: [Therion] Multiple fixes for the same point

[Martin Sluka via Therion]

To average it before (in GPS software) and to add all three as comment?

m.s.


On Sep 07, 2017, at 02:08 PM, Andrew Atkinson via Therion  
wrote:

I'm sure that this has been covered, but I cannot find it anywhere.

I have 3 different gps results for a surface point, all taken with the
same gps but on different days, so rather then picking one I just used
fix on all 3.

However, therion appears to be taking only the last one I enter.
This does not seem to be the right behaviour! Is there a way for Therion
to take all 3 and 'average' them?

thanks in advance

Andrew
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