I found this posted from 09.
"September 2009 - 07:04 AM
The iPhone uses GPS technology for finding its position, not cellphone positioning. It works fine when out of phone service range.
That being said, the GPS in the iPhone is not nearly as accurate as what you find in marine electronics. The "sampling rate," or whatever it's called, is also much lower so it can't calculate speed and direction accurately.
I'll use my iPhone for casual use on the road, but I'm not getting underway without good marine electronics on my boats. I've never seen a mobile phone with a radar either! :-)
Captain Ethan Maass
Sea Tow South Shore
(Cape Cod Bay area)"
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Looking for some information. I currently have a Garmin iQue M5 PDA/GPS that I use for hunting with topo maps and as a backup to my chartplotter on my boat using NOAA free maps. This unit is starting to show signs of failing. I am looking at replacing it with another PDA/GPS or preferable a iphone, droid, windows 7 phone, etc. I have several questions I have not been able to get answered talking to the phone people from the various services(att, Verizon, etc)
Below are some of the questions I have and was hoping that some of the boaters on here may be using them and can shed some light.
1. Make and models of phones you are using out in the open water?
2. Some of these phone use aGPS and/or GPS. If 12 miles off shore and no cell service will the aGPS still
track and keep showing your current location or do they only use the cell towers to triangulate your
location?
3. Do I need to get a phone that has GPS and aGPS if they make them? Brand, model?????
4. Software or apps for these phones…and recommendations? I have seen one by memory-map.com that makes the
software I use on my PDA now makes an app that can be used on and iPhone
http://www.memory-map.com/mm-iphone.htm . Has anyone tried it on an iPhone and not have cell service?
5. What about apps for the other phones?
Thanks for any help you can provide.
Lanny