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

Sean Edwards sean.r.edwards at btinternet.com
Sat Mar 21 07:02:01 CDT 2009

Adobe Photoshop reveals more GPS data that was transferred to the camera 
image, than does Adobe RAW:

exif:GPSLatitude: 51,8.7942N
exif:GPSLongitude: 0,42.73W
exif:GPSAltitudeRef: 0
exif:GPSAltitude: 107761783/1000000
exif:GPSTimeStamp: 2009-03-14T07:43:15Z
exif:GPSStatus: A
exif:GPSMeasureMode: 3
exif:GPSSpeedRef: K
exif:GPSSpeed: 2/10
exif:GPSTrackRef: T
exif:GPSImgDirectionRef: T
exif:GPSMapDatum: WGS-84
exif:GPSDestBearingRef: T
exif:GPSDestDistanceRef: K
exif:GPSDifferential: 0

Incidentally, although WAAS/EGNOS was always set as 'enabled', EXIF data say 
"GPSDifferential: 0" on every shot I have looked at. Garmin say WAAS/EGNOS 
can degrade accuracy to less than that provided by GPS satellites alone, and 
that for this reason when WAAS/EGNOS is enabled on the Garmin receiver, it 
automatically uses the method that achieves the best accuracy. The general 
view seems to be that EGNOS at least is not of much use.

Adobe RAW data:
>> 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

>> ----- 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

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