Pentax O-GPS1

[materialsguy]

After a long waiting period, I finally nabbed an O-GPS1 for use on my 645D.  The short conclusion is that it does exactly what it is supposed to do, and works just like my Nikon GPS unit does, which is a good thing: non-intrusive and works as advertised.  One thing that the Pentax unit does that the Nikon does not is time sync.  In other words I never have to set the clock on my camera again. The O-GPS1 will sync the camera's clock to UTC + offset automatically.   
I think the cesium and rubidium clocks on the GPS sats should be accurate enough for my purposes....

Cold start with open sky view is about 45 seconds to 3-D lock.  Warm start is under 10 seconds to 3-D lock.   I cannot use any of the astro functions with the 645D, of course, but the electronic compass could be useful.