Best GPS For Speedometer?

I have a need for a speedometer for my ATV (helmet mounted - not attached to the bike). Can anyone recommend the best GPS device for that? Price is very important but I want something I can use to do real-time speed sensing.

Thanks!

I don't know about helmet mounted but I have a little garmin etrex that does speed readings very well.

I have one of those too but I have a number of ATVs and motorcycles and I've never been able to get it mounted well on any of them. I've broken 2 jumping..

Oh, and I was speaking of a GPS module to interface with the arduino ;-)

I know that you wanted GPS recommendations but have you considered just interfacing with the existing speedo (if it's electronic) or using a hall effect sensor or something? Do all of the electronics have to be in the helmet? Obviously this would require some sort of wireless link between the vehicle and your helmet.

Do you plan to support multiple vehicles? If you are using just one ATV it might be more economical and reliable to go with a non-gps speed sensor. GPS is decent but it's not always terribly reliable. I've had a lot of trouble with some GPS sensors not wanting to get a signal in a variety of situations and that's annoying. I just don't think that you'll be able to count on the GPS to always be up and reporting your speed.

Depending on your requirements the GPS might be the way to go or it might be a continuous thorn in your side.

Hi AdderD - thanks for the reply.

I have a number of bikes and ATVs so I don't want a vehicle mounted unit. I'd like something I can take with me on any bike I want to ride.

I've used a Garmin eTrex with me on several rides reliably so I'm not too worried about GPS signal. I don't need exceptional accuracy in any case. +- 4 or 5 MPH would be just fine for my purposes.

There are two problems I'm trying to solve. First is a way to see my speed without taking my eyes completely off the trail (to look down at the dash), and second, a data log of the entire ride. I plan on logging to an SD card so I can route our rides on Google maps.

From what I've been able to read since I posted this it sounds like just about any GPS module will work. I'll probably look at one of the 5Hz models. If anyone has any recommendations, though, I'm all ears! Thanks!

GPS speed is typically specified at 0.05 m/s accuracy which is the equivalent of +/- 0.11 mph. Any GPS you find will most likley be close to this in terms of speed accuracy.

As for a 5Hz GPS you can get similar or even better performance also with a standard 1Hz GPS in combination with an Arduino. If you keep track of acceleration/deceleration (difference in speed between readings divided by time) you can account for this and refresh your speedo at 10Hz or more if you think it makes sense. There is significant inertia in a vehicle so at moderate to high speeds, such predictions will be highly accurate.

Unless you find a 5Hz GPS that is the better choice in terms of price, size or power usage it does not really add value for this type of application.

3m makes some hella good velcro-like stuff for mounting stuff and it is STRONG. in fact I have alot of it... if you need some just pm me :)

http://cgi.ebay.com/Arduino-GPS-Netduino-GPS-receiver-w-tutorial-Sparkfun-/250686123796?pt=GPS_Devices&hash=item3a5e0eaf14#ht_499wt_1048

I got this gps unit and it currently is used in my data logger. It works great and best of all it was cheap.