[Taxacom] GPS units that record the time a waypoint was taken, accuracy, datum -- postscript

[Sean Edwards]

As a post-script to the below, I've checked a number of my images, and find 
that most are lat/long with 4 decimal point minutes. The answer to my 
question may be just that both Adobe RAW and Photoshop drop trailing zeros, 
though they seem to do so more than 10% of the time! E.g. 60x 4s, 8x 3s, 2x 
2s, and the truncations are (almost) always longitude, and clustered not 
random. Going back further, some days are all 4s, whilst other days have 
many even most longitudes truncated. The GPS unit is set to British Grid, 
but always shows the full 10 figure read out.

So an alternative explanation is that the camera picks up the unit's 
assessment of accuracy, not showing what it considers to be spurious 
precision?

This would be remarkable? Is this possible?

~~~~~~~~~~~~~~~~~~~~~~~~~

Sean Edwards
email: sean.r.edwards at btinternet.com



----- Original Message ----- 
From: "Sean Edwards" <sean.r.edwards at btinternet.com>
To: <taxacom at mailman.nhm.ku.edu>
Sent: Friday, March 20, 2009 1:01 PM
Subject: Re: [Taxacom] GPS units that record the time a waypoint was 
taken,accuracy, datum


> An example from the EXIF data of a recent GPS tagged image (Canon EOS with 
> Garmin GPSMap):
>
>
> Latitude 51,8.7942N
> Longitude 0,42.73W
> Altitude 107.76 m
> Time Stamp 14/03/2009, 07:43:15
> Speed Ref K
> Speed 2/10
> Track Ref T
> Image Direction Ref T
> Map Datum WGS-84
> Destination Bearing Ref T
> Destination Distance Ref K
> GPS Differential 0
>
>
> Note the difference in decimal points between lat (=4) and long (=2) 
> minutes...  Why?
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Sean Edwards
> email: sean.r.edwards at btinternet.com
>
>
>
> ----- Original Message ----- 
> From: "Finn N. Rasmussen" <finnr at bio.ku.dk>
> To: <taxacom at mailman.nhm.ku.edu>
> Sent: Friday, March 20, 2009 10:10 AM
> Subject: [Taxacom] GPS units that record the time a waypoint was 
> taken,accuracy, datum
>
>
>> Do the programs and gadget that transfer GPS-info to, e.g., cameras,
>> also transfer information of the geodetic datum used when recording this
>> particular set of coordinates? If not, the accuracy is less than 2 km.
>> Many field collectors seem to be unaware of the importance of the
>> geodetic datum. When reviewing taxonomy papers that include geographic
>> coordinates with great details I always demand the datum [e.g. EUR50,
>> WGS84 or RT (if in Sweden)] mentioned, or fewer digits included. It
>> often turns out that authors don't know what I am talking about!
>> Finn N Rasmussen, Dept. of Biology, Univ. of Copenhagen