Position Accuracy - Raytheon 420 GPS

[Ron Parkes]

I have a Raytheon 420 Chartplotter and GPS on my 320 and consider it to be very useful. One of the indications on the unit is FDOP which gives you a measure of "goodness" of position fix. I have a Garmin 175 handheld which I use as a backup, and it gives you a similar indication but also translates the goodness into an estimate of positional accuracy in feet i.e., 16 feet.Is there a rough estimate of translating the FDOP measure from the Raytheon 420 into feet?? The reading I normally get with about 11 satellites acquired is around .9Ron Parkes s/v Contemplation

 

[bill walton]

GPS accuracy

This subject always generates controversy and discussion. I think non-differential GPSs are generally said to be accurate to 15meters. The Raytheon has a chart showing the relative accuracy on a standard, differential and the new WAAS units. They've plotted the gps generated location of a known point over time for each of the types of systems. If your handheld says it's good to 16ft, I'd be suspect because that's only 5 meters which is incredibly accurate.