Was looking at one today as we were going across the bay, definitely a little slow on acceleration but it did read max speed 104.7 which should have been about right.

Did you downgrade to a Fountain????

Mine is dead on with the GPS in my work van.

Phone GPS are triangulated off of cell signal. So depending on your signal and proximity to towers will determine accuracy. My iPhone was almost spot on with my Garmin in the Detroit River. However, when I got out into Lake Erie, it was off by a few MPH..

Hello there. Check this one out. like I said in the video. The 2 Garmin and the Galaxy S3 4G. are always with in the same tenth.

http://www.youtube.com/watch?v=clQPWsgydrA (or google carapi+donzi) Regards Bjorn Carapi

That would explain the issues while running off-shore. If you are only in range of one or two towers then it will be off.

iPhones have GPS built in. They do not rely on cell towers for location services, although their satellite locking hardware is likely not as sophisticated as a full marine GPS, you should be able to get very accurate numbers from it nearly anywhere in the world. in fact if you are near cell towers as mentioned. the iPhone may be more accurate than a marine GPS since it has multiple modes of triangulation to determine location.

X2 on this. Mine is dead on, like others have stated its a little slower to update speed.

you using speed wax? that would explain it

I´m not claiming to be un expert on GPS devises but from my own experiences with Garmin marine GPS (not the latest models )and by compairing them with technology like the samsung Galaxy S3 4G i find the difference first to be the that the galaxy find it´s satelites in no time ,like when you press the map button on the S3 . It´s there instantly. The Garmin 182C marine could take more then a few minutes before it´s ready.(The phones and the marine GPS always shows the same readings at the end by a tenth) There was a big test when they compared sport/running watches like Garmin forerunners and the Polar series with a modern iphone app.They all got their ass whipped by the phones. I´m a runner to and today like often my GPS sport watch(Garmin 110 ) took close to 5 minutes to be ready.My Galaxy is there directly. I´m not a sales man for Samsung just compairing different ways of measuring "landspeeds" accurate. Would really appreciate un expert on the subjekt to comment. I´m guessing here but the thing seems to be how many satellits the device are shooting at or being able to use. ??