For a while I use a Foretrex 201 to get some better idea regarding tacking angle, speed and distance. The GPS works generally well. One of the features is a max speed-reading which seems to be off. My max speeds saved in the unit can be somewhere between 25 m/h to 67 m/h. Does someone else encounter the same problems with the foretrex units?
Thanks,
Patrick
You will need to use an average speed to get accurate numbers. Most GPS's will have spurts of inaccuracy which will cause the max number to be pretty far off. Your unit can give you the numbers over a period of time you can get your own average, or looking at the numbers you can determine what your max number should be.
Clayton
make sure you reset the "trip computer" before you try to obtain your max speed. I left my GPS on in the car once, and then after I sailed around the lake I was curious as to the max speed.
78mph.
yeah right 
Yup; ignore the Max speed, it's not very accurate;
I always reset my 201 as I am heading out on the water. I stop the unit when I am coming back in to the dock/beach. When I get home, I download the info to Garmin Mapsource Software and it will show you your tracks and detailed information. It will show max speed and many other details.
Terry
Clayton... most of the time when it blows and I get close to 20 m/h I do not find the time to look at the display.
Reseting the unit... I reset trip and max speed every time - but I end up with odd readings for the max speed. But the same thing happens when I take the gps jogging - speeds 2x or 3x the speeds that I would expect.
Terry... what type of mapsource do you use?
Thanks Patrick
Well, on my GPS it tells me the accuracy of the unit at any given point. I think the best is within 12 feet, but most often runs between 23 to 44 feet. Given that the unit is telling me that, I would expect the speed reading to be "off" in a short time frame, but to be more exact over a longer time frame.
Good luck,
Rich
Terry
Me too ; it gives you a plot and, speed and direction etc. It came bundled wit my GPS V
Rich... My old waas enabled magelan seems to do better when it comes to accuracy. At the same time I would hope that the units would compensate for those inaccuracies because otherwise the max speed would be all over the place. Not sure what the samplerate is - assuming the unit samples a few times a second - having those samples taken up to 40 feet apart would result in high speed readings while standing still.
What type of Garmin Mapsource Software are you using? Anything available for marine use? Just some topographic map? Thanks
Patrick
I use Garmin Mapsource Metroguide USA. I originally got the software to download detailed area maps into my Garmin GPSMAP76. I now use it more to store my recent races/trips. It is great when you are just out sailing/practicing, as it will show you, on a detailed map, where you have been/how far you went/maximum speed/average speed/etc. It shows a lot of info. Interesting to see elevation changes. I sail on a lake and there are not a lot of elevation changes! When I see one, I like to think that I was "flying high" 
.
As to detail, the trip is saved with a series of points (bread crumbs) that show you the speed/heading/time/elevation between each point. One good trip consists of hundreds of points. You can look at a series of points to determine where and what your maximum speed was. If the speed is not consistant for at least a few hundred feet, I would imagine that you were flailing your arms about and you would be getting your maximum "arm" speed...
Could not find the software on Catsailor Online Store. If I over looked it, maybe Rick can point the way. It is found at http://www.amazon.com/exec/obidos/t...
The software is very detailed and even has "hazards" that are common to the lake I sail on (in Oklahoma).
Terry