Nav
 

How can I pull up ground speed on the GPS. I heard people talking about it before but I can't find the link.

you can't

yeah you can! serch my posts using "joystick" as the key word and then look a post or 2 above mine.

We covered a lot about the NAV's back doors in this thread. You can get the speed through the NAV, but it's not very accurate or visible while driving...

There's yet a different menu screen as well that gives a more accurate text reading, but still not perfect:

1. Open the menu
2. Choose "setup menu"
3. Choose "system information"
4. Choose "version"
5. Push the joystick forward 3 times
6. Push the joystick rearward 3 times
7. Push the joystick forward 2 times
8. Select the second menu option- something like Vehicle Sensors

This screen displays vehicle speed in km/h, voltage reading, and the gyro output voltage. I was toying with this on the way home and quickly realized this isn't GPS measured speed, but input from the vehicles speed sensors.

As I mentioned in a different thread, my speedo reads high because of my slightly lower profile snow tires, but I also suspect an inflated reading intentionally put in by Mazda as they have done on the Miatas as well. Someone with OEM tires should see if this Nav measurement differs from their speedo- I'm curious if mazda just dummied up the digital speedo, but let the real speed signal be fed into the nav. Another thing to note is the speed on this display is not very granular- once you're out of the teens, it seems to only move in increments of 3km/h, and slightly slower than real time. I suppose this is used for the nav systems' "dead reckoning" mode when it can't get a solid signal from GPS so it keeps tracking you based on your speed and gyro inputs combined with a known path you're on when you lost signal.

There is a screen with GPS signal information on it (longitude, latitude, altitude, speed, and compass direction), but for some reason the speed and direction are not updated on this screen- they always say 0km/hr and North.

What I thought was neat was watching the reading the nav is fed from the DSC's gyro unit... it's surprisingly sensitive. At +2.5V, you're going straight... anything higher and you're turning right, and anything lower, you're turning left. The problem comes in when you're trying to pull as many G's as possible on a hard turn to see how high or low a reading you can get... kinda like your own personal skidpad :P

It is plainly visible at the top of the Garmin iQue 3600's screen ;-)