[Therion] Multiple fixes for the same point

[Philippe Vernant]

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 <therion at speleo.sk> 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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