[OSM-talk] Photo_mapping - How to put EXIF data into a jpg image

Andrew Gregory andrew at scss.com.au
Mon Feb 22 02:38:39 GMT 2010

On Mon, 22 Feb 2010 13:03:40 +1100, Greg Troxel <gdt at ir.bbn.com> wrote:

> John Smith <deltafoxtrot256 at gmail.com> writes:
>> On 22 February 2010 06:10, Jochen Plumeyer <jochen at plumeyer.org> wrote:
>>> Be aware of your time zone (and daylight savings timezone as well) of  
>>> your
>>> camera, as GPX times are all in lon=0°/ Greenwich/ UTC/ Zulu time.
>> Actually they are in GPS time, and have an offset in seconds from UTC
>> embedded in the signal.
> Huh?  I realize that GPS internally computes in GPS time (!= UTC, !=
> TAI), but I have never seen an actual device output a track log in GPS
> time - it's always been UTC.

The GPS/UTC time offset is sent as part of the almanac data. Effectively,  
if you have a position lock, time will be in UTC. Most GPS receivers can  
output the time before achieving a position lock. That might be UTC or it  
might be GPS time, depending on if the almanac has been received or not.


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