diff --git a/handbook/survey/gps.htm b/handbook/survey/gps.htm index 1fa06c8d8..11ba9424c 100644 --- a/handbook/survey/gps.htm +++ b/handbook/survey/gps.htm @@ -42,15 +42,29 @@ the GPS on the point. Don't build a cairn, they don't last for decades and we ha minute to get a fairly good fix (the first figure reported may be quite a way out is you have been moving). Then mark the point as a waypoint (dedicated GPS devices or GPS apps only). + +

Camera locations

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Even if you have no intention of using your location or recording a track, the camera in your phone will record locations of your photos which are extremely useful to future expeditions - for reasons which only become apparent when you yourself try to work out what someione did 10 years previously. +

Camera photo locations are not
on the track!
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Your camera will use the same location settings as the rest of your phone, but sometimes with a bit of a delay. We have lots of examples of geo-located photos where the recorded location is alctually the location of the previous photo because someone has taken a quick photo but the phone hasn't had time after waking up to get a location, so it uses the previous one! And doesn't tell you!! + +

So when taking a photo of an entrance, always take one photo; delete it, and take another. This will give your phone a chance to get synchronised properly. + +

ALSO: always take 3 photos of any entrance, the obvious one about 10m away, a scene-setting one from 20 or 30m away, but also a really close one of 3 to 5m away, so that we can see if rocks have moved around the entrance and also for a much better identification in future. If there is a tag, always take a close-up photograph of it so that the letters are readable.

Averaging

If you're feeling really keen and have a dedicated GPS device or sophisticated GPS app, -you can set it up for averaging, which gives a more accurate fix – some GPS receivers +you can set it up for averaging, which used to give a more accurate fix – some GPS receivers support this automatically, and with others you can just leave it recording a track log, then record another waypoint at the same place just before you leave so it's clear to someone examining the track log when you actually left.

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Averaging used to be very important, but today (2025) we have so many GNSS satellites in the sky that ionospheric effects are the significant error. These change slowly over 5 hours or so, so avergaing for a minute or and hour does nothing useful. You would need to average over several days. The solution for a fast fix is to use RTK. +

While the GPS is averaging your location, you can do something useful (like rigging the cave, doing a surface survey from the GPS point to the marker spit, looking for other caves, or even having lunch!) Remember to stop