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WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through April 01, 2004 » Cheap GPS speed indicator? « Previous Next »
By FL SurfLover (flsurflover) on Friday, February 27, 2004 - 12:52 pm:    Edit Post Delete Post
Does anyone know where to get a very low priced handheld GPS unit that displays speed? I want to calibrate my PerfectPass and original speedo and I don't know anyone that owns one.

Manufacturer, model, price, and website if you know them.

By Kevin R Baugh (krbaugh) on Friday, February 27, 2004 - 1:25 pm:    Edit Post Delete Post
You can get them al most anywhere

By thomas ryan (g3revenge) on Friday, February 27, 2004 - 1:46 pm:    Edit Post Delete Post
most gps's require movement to generate a location. the more expensive units have a magnet/compass built in for greater accuracy.

their is a write up on a few units in this month scientific american comparing magelens(sp) and garmins. pretty good comparisons on accuracy and ease of use.

wal-mart sells them cheap, but i boycot wal-mart.

you can hit the ski course with stop watch and get your calibration fairly close. skiertoskier has a timing chart.

By Kevin R Baugh (krbaugh) on Friday, February 27, 2004 - 1:59 pm:    Edit Post Delete Post
now your going to have to explain how a magnet/compass would be used for more accuracy

I have owned 2 very low end gps they both gave accurate locations as soon as they triangulated the position from multiple satellites. No movement required

By Rod McInnis (rodmcinnis) on Friday, February 27, 2004 - 4:37 pm:    Edit Post Delete Post
If you just want the GPS to calibrate your speedo, borrow one! I think they pretty much all will indicate speed.

Be advised that the accuracy of the GPS unit will depend on the position of the satellites when you run the test. If you get a favorable selection of satellites, the accuracy can be very good. If your luck isn't so good then your results won't be either.

You also need to factor in any current that might exist. If you are on a lake, then the current will probably be negligable. This will not be the case on river, and might not be the case on a body of water that was subject to tidal action.


By thomas ryan (g3revenge) on Friday, February 27, 2004 - 5:24 pm:    Edit Post Delete Post
sorry kevin, i meant heading or direction.

here's the clip.........A GPS receiver can provide accurate information about its position and velocity, and from the velocity vector it can determine the direction in which it is moving - called the course or track. The accuracy with which a receiver can compute this direction depends on its speed (the velocity magnitude) but is usually better than one degree for speeds greater than about 10 kilometers per hour. The course is not necessarily the same as the heading or direction in which the GPS receiver, or the platform on which it is mounted, is pointing. A single-antenna GPS receiver cannot determine heading. However, a compass can provide this information and as mentioned earlier, some GPS receivers incorporate an electronic compass, usually a two-axis sensor. Some receivers have three-axis sensors that give relatively accurate bearings even if they are slightly tilted.

As previously mentioned, the firmware in a GPS receiver contains a model of the main field - whether or not it has an embedded electronic compass - from which it can compute the declination value at the receiver's current position. So the receiver can convert a course referenced to true north to one referenced to magnetic north. Likewise, it can convert true bearings to magnetic ones.

A GPS receiver's compass allows the use of a navigation technique known as sight and go. The receiver displays a compass ring with a pointer. Holding the receiver horizontally near eye level, the user lines up two sighting marks on the receiver case and the pointer with a distant object and instructs the receiver to "lock in" the direction to the object. The receiver then continuously updates the object's bearing as the user follows an arbitrary path toward the object.

The compass module in a GPS receiver usually can be switched off to conserve power. The receiver can also be configured to switch its display from compass heading to GPS-derived course once a certain speed, 5 or 10 kilometers per hour for example, is achieved. The receiver can be set to revert to the compass when the speed drops below the threshold for a preset number of seconds.

A single-frequency GPS receiver also must know something about the geomagnetic field to compute an estimate of the delay experienced by GPS signals traversing the ionosphere.

the whole article which historical rhetoric.http://

By Thomas (h2oskeefreek) on Monday, March 01, 2004 - 6:10 am:    Edit Post Delete Post
get a Garmin Geko. 120 bucks tops. PLENTY accurate enough. I sell these things, and the differences between the high end and low end are negligible. If all you want is speed, GEKO is the way to go.

By badzuki (badzuki) on Monday, March 01, 2004 - 8:45 am:    Edit Post Delete Post
I just bought a Garmin etrex Legend for $150. It is awesome. It has a trip computer that tells: speed, top speed, average speed, average moving speed, stopped time.
Along with all that is has elevation and a basemap of North America. We just took it on a trip this weekend and used it to find a hotel. It has points of interests. Just lookup the next exit and there was the hotel we were looking for.
Also I can hook it to my laptop and can display the current position and track movement.

The real reason I bought one is becuase between my boat and the three other boats I ride in, pp varies alot. Well not anymore.

Go buy one, it well worth the money. Lot of fun.

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