From: Ralph Hartley (hartley_at_aic.nrl.navy.mil)
Date: Fri Jul 12 2002 - 20:57:28 CEST
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Richard Knapp wrote:
> Ralph Hartley wrote:
>>Richard Knapp wrote:
>
>>>When COMPASS does loop closure
>>>("corrected data"), it creates a copy of the DAT file with new
>>>distances, azimuths, and inclinations (and sometimes survey ties).
>>
>>Does it?
...
>>There may
>>be some Compass options or something that do this
Several people noted that this is the case.
> I don't see any problem with putting loop closure information in the
> data file as long as it is clearly labeled.
I agree.
> The would be a problem on shots with multiple measurements: back and
> front sights or just multiple azimuths/inclinations. It might be more
> distinct - for lack of a better term - to keep that information out
> of the Measurement Element. (Again, for lack of a better term...)
> Maybe something like:
...
> Measurements do not address compiled/absolute coordinates, just the
> raw data items (azimuth, distance, inclination).. unless I'm reading
> the text wrong.
Then closure is not a measurement, and shouldn't be called one. (I have
to admit I haven't read the document at all.)
>>Also there is a data safety issue. If even one shot is missing, (due to
>>file corruption, deliberate editing, or if the data is in several files
>>but you don't have them all) then some or all of the position data is lost.
>
> That would be just as true for multiple files as it would for a
> single file; any file can be corrupted, especially with all the junk
> (ie virii) running around on the net these days. Which is why it
> seems reasonable to have the compiled (coordinate data) in one,
> separate file instead of in many files.
You asked if there was any difference between storing (x,y,z) and (delta
x,delta y,delta z), since you can compute one from the other if you have
all the shots availabe.
I was pointing out that, if there is even a single shot that don't have
(through accident or design), then (x,y,z) may contain *more*
information than (delta x,delta y,delta z).
So there is a difference, and if you need to choose just one, you should
choose the less brittle (x,y,z).
You were asking if (x,y,z) data needs to be stored at all. I was noting
that it does.
Ralph Hartley
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