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need help on deciding which GPS unit to get


Gleb
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I recommend the Garmin eTrex Vista series---several diff. models, all good. I have the eTrex Vista C---which has a color screen plus 24MB for maps (lots of coverage). Got it for $250 on sale at REI. (The others are less, main difference is monochrome vs. color and amount of on-board memory.)

Scott

I don't care much for the color and I only really need it for speed and altitude and $250 is a bit pricier than i would want.

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Gleb,

I have done a bit of work with using GPSs for velocity measurement. All the Garmin units are pretty good. A $100 Etrex will work as well as a $400 GPSmap 76. They both record MAX speed accurately. What they don't do so well is log your speed and position over multiple points. The track log is OK but the speed data is irregular (generally at least several seconds between track points) and, with some units, it is considerably less accurate. The Geko is a little smaller than the Etrex, costs a little more but should have the same GPS engine. Both are reasonably waterproof.

As an alternative, Delorme sells a logging gps called a Bluelogger for $149 bundled their StreetAtlas software (an Etrex with a data cable will be nearly as expensive). It records date, time, position, velocity, altitude, heading and signal quality every 2 seconds. It will record 50,000 data points (over a day at 2 second intervals). The battery will last 10 hours in warm temperatures although I am not so sure about cold conditions. It is not waterproof so a plastic bag or box may be necessary. The bluetooth connection can be a pain for BT illiterate people like myself. The data is accurate (speed measurement uncertainty is better than 0.2 mph-same as Garmin). The 2 second interval gives frequent enough data points that you can make reasonable estimates of things like lateral acceleration and turn geometry. You can put the data on their mapping software if that is of interest. I usually load it into a spreadsheet for analysis.

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Another logging possibility is using the Etrex or other GPS and hooking it to a Palm Pilot running Cetus software. This involves more money if you don’t already have the Palm.

Getting good data requires a good view of the sky. Most jacket pockets don't work so well. Taping the GPS to the board should be pretty good. Taping it to your shoulder (even inside your jacket) might be fine as well. Logging has an additional advantage. If you have bad data it will be apparent from the log. Either the data won’t change from point to point or it will change abruptly. The number of satellites in view will generally be less than 5 if this is happening.

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Let us know what you find.

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Bob

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