I use Expertgps software (http://www.expertgps.com) with my Garmin 12 GPS. The newer GPSs have more options, but it works for me. The software downloads the map image over the net and then overlays the tracking on it. You can zoom in for a more detailed map if you wish. It also offers the use of aerial photos, instead of Topo maps. Some new GPSs come with a data cable to hook to your computer and it's own software.
Jack

AS USUAL woo is waving his ignorance around like a big flag saying "Look at me, I am stupid, but I like to talk about things I know nothing of".
Just another big dent in his sad excuse for credibility.
Do some more trig calculations for us woo.

hello

for measuring the speed, the inaccuracy (position offset) isn't the most imported factor, as long as the position offset stays the same during the intervals of measuring.

I've got an Etrex Legend and the Garmin Roads and Rec. software...just liked the detail of those images better. Thanks!

lets not turn this forum into a place for name calling and insults. that is what the old forum is for. wouter may have been wrong regarding the selective availability, but his other input on this subject was right on.

as an aside, it amazes me how brave people turn behind the anonanimity of the internet. i wonder if you would take the opportunity to jump into a conversation where people could see who you are and make such a comment. i had already corrected wouter, as did kevin rose. neither of us resorted to name calling. in general, poeple get more respect by not commenting about someone rather than commenting negatively.

[color:"green"]>lets not turn this forum into a place for name calling and insults [/color]

Dave,

Today I was disturbed to see a trail of posts that were reminiscent of old forum antics, slamming folks right and left. Thanks for stepping in and encouraging restraint.

Cheers,

>Took my Garmin Legend skiing over the holidays and it showed the max speed of 264 mpg. I should be dead now.

>Perhaps due to the mountains and the GPS was in my front coat pocket, there might be a bit of inaccuracy.

Did you ride in an airplane to or from your ski trip? I have made that mistake before, forget to turn the GPS off before boarding then your max speed shows some insane number...

i read about a glitch in the software where it will calculate the speed based on where you were when ou last turned the unit off and then turned it on after moving. it sees a large distance moved in what it thinks is a small amount of time. in particular, i heard of a reported speed of over 6000 miles/hr for a guy that was hiking. like everything you hear in life, it is up to you to decide whether or not you want to believe what the gps tells you.

Ok folks...

Whats the answer to this simple question.

At about max speed... aprrox 22 knotts true boat speed. What is the accuracy and the precision of your standard cheap consumer GPS. ... ie 22 knots plus or minus X

At 3 knotts true boat speed... what's the error?

Finally, How long must you be measuring for this kind of precision?

>AS USUAL woo is waving his ignorance around like a big >flag saying "Look at me, I am stupid, but I like to talk about >things I know nothing of".
>Just another big dent in his sad excuse for credibility.
>Do some more trig calculations for us woo.

Boy, this post makes me want to go out there and just sail!

How does this post fit in with the accuracy of GPS?

Regards,

Mary, Rick:
Is there some mechanism we can use to vote people off the site if they are being abusive?
David

from MY experience, using a tachymeter on a stopwatch, a speedometer, and a known distance, i have typically seen differences of less than 0.2 miles/hour at speeds below 80 miles per hour (i wasn't driving, so don't tell me i was speeding).

i looked at the previous posts by sam and besides the last two days, his posts were generally positive and useful. how about we just chalk this one up to him having a bad week and move on for now.

There is nothing anonymous about me.
I usually race in VA, NC, SC, GA, & FL on a Hobie 17.
I was at the MEGA last year.
I have attended every Spring Fever Regatta and expect to attend the next one.
I have met woo face to face.
If the newbies(pre-new forum) had read as many insults and lies from woo as I have, they would have a different perspective.
I reached my "Woo-garbage" limit long ago.
He just needs to be reminded occasionally that some of us haven't forgotten.

on second thought, maybe not.

>how about we just chalk this one up to him having a bad week and move on for now.

We were resetting the max speed after every run. I forgot to turn if off once on a plane and recorded 423 mph. Go SWA.


>Took my Garmin Legend skiing over the holidays and it showed the max speed of 264 mpg.
>Did you ride in an airplane to or from your ski trip? I >have made that mistake before, forget to turn the GPS off >before boarding then your max speed shows some insane number...

Hi Mary...

Doesn't it seem that things are getting overwhelmed with too much technology? Why not try it the old fashioned way? Get a long piece of light rope or cord, tie a knot in it (or mark it) every 47 feet, 3 inches. Attach a heavy piece of wood or other floating sea anchoring device to one end. When underway, toss the wood off the stern (the rope must be able to pass freely over the stern).
After the first knot passes over the stern, time for 28 seconds, then stop the rope. You could turn your boat around and collect your wood or just drag it aboard. Count the number of knots that went over the stern during the 28 seconds (after the first knot). You have your speed in knots.

A thousand feet of rope should be enough to show up to 20 knots. I suppose 500 feet would work if you timed for 14 sec. and then doubled the number of knots that were counted.
1500 feet of rope (or 750 feet then double) would be needed to determine a speed of 30 knots.

Any current helping your boat along would also be helping your piece of wood along, cancelling out any bonus speed reading.

Of course, GPS is a bit easier!


Mark Owens
1976 H16 sail # 19857

Actually, in my original question, I had added "other than a knot log," but I deleted it, because I didn't think anybody would even suggest it. I'm an old-fashioned girl, but I didn't know there were any old-fashioned boys out there. Thanks for the explanation of how a knot log works.

Talk about...... RETRO!