Dumb question...

[KC_Daytona]

I really like the GPS gauges, but what happens when you
loose GPS signal? Is there an antenna?

Thanks

[rthomas98]

yep. it is a magnetic that you got to find a place for. I put mine under the body on the top right side of the windshield.

[edwardb]

X2 on the external antenna and mounting under the body. I've done three builds with the Speedhut GPS antenna setup. I can count on one hand the number of times the needle briefly bounced around a bit between the three and thousands of miles. Otherwise rock solid.

[Papa]

If you lose the GPS signals (you need four satellites to produce a location and calculate your speed), your speedo will not register a speed. Thankfully, there are over thirty active GPS satellites on orbit with about 10-12 of them visible at any given time. This is what the antenna looks like.

https://thefactoryfiveforum.com/attachment.php?attachmentid=170975&d=1660359584

[David Williamson]

I put the antenna on the dash far left side, it's small and not very noticeable. Works well but it does lose signal in tunnels or underground parking garages but not a big deal.
David W

[Jim1855]

Looking at the big picture, how serious do you think losing the GPS signal and speedo indication is? Earth shattering or just a short-term annoyance? Will you need to stop driving because you don't know the speed? After a while of driving the tach will give you reasonable guidance for speed, or at least to compensate for the lack of speedo. OK, you'll lose mileage but is that really a deciding factor?

Often, it's the turn-on delay that is more bothersome. The Speedhut GPS speedos have an always-on signal to minimize the delay.

I've been using a GPS unit for years, same basic technology as the GPS speedos and seldom lose signal. There are a few tunnels, The Eisenhower on I-70 for one, but so what.

Jim

[Joel Hauser]

Here is a related question. Many cars have a vehicle speed sensor VSS in the transmission that not only sends vehicle speed info to the speedo but also provides data to the computer/engine control module ECM for engine performance adjustments. If you install a GPS driven speedo, do you still need the original VSS drive in the transmission to send data to the ECM, or does the GPS unit also provide that info to the ECM; and if you lose GPS signal (driving through the Lincoln Tunnel under the Hudson River, for example) will that cause any trouble?

[Papa]

Here is a related question. Many cars have a vehicle speed sensor VSS in the transmission that not only sends vehicle speed info to the speedo but also provides data to the computer/engine control module ECM for engine performance adjustments. If you install a GPS driven speedo, do you still need the original VSS drive in the transmission to send data to the ECM, or does the GPS unit also provide that info to the ECM; and if you lose GPS signal (driving through the Lincoln Tunnel under the Hudson River, for example) will that cause any trouble?

The VSS is a pulse signal that the ECU uses like most sensor data. GPS signals received through the antenna are completely different. The GPS speedo has a GPS receiver in it that uses those signals to calculate your speed. There is no VSS output from the speedo that will feed an ECU. If your ECU requires a VSS signal, you'll still need that to come from the transmission.

Edit: Here's a simplistic GPS tutorial for those that are interested.


https://www.youtube.com/watch?v=wCcARVbL_Dk

I actually worked on this system for many years, so it's a bit near and dear to my heart. :)

[Papa]

A little more for the geeks in the crowd. Here are the calculations that your GPS receiver is solving simultaneously over and over again:

https://thefactoryfiveforum.com/attachment.php?attachmentid=170990&d=1660410489

PR is Pseudo Range (distance)
c is rate (speed of light)
t is time
x, y, and z are the satellite positions in coordinate space

So, as you see, this is just a very complex version of the rate x time = distance word problems you learned to solve in school.

[rhk118]

A little more for the geeks in the crowd. Here are the calculations that your GPS receiver is solving simultaneously over and over again:

https://thefactoryfiveforum.com/attachment.php?attachmentid=170990&d=1660410489

PR is Pseudo Range (distance)
c is rate (speed of light)
t is time
x, y, and z are the satellite positions in coordinate space

So, as you see, this is just a very complex version of the rate x time = distance word problems you learned to solve in school.

Yikes, I’ve always just gone by gear I’m in and revs…seems easier than that, holy smokes…haha…obviously you have to be familiar with the car before you develop that speed/rev sense…

[Windsor]

Wanna see GPS satellite locations realtime?

https://satellitemap.space/?constellation=GPS

You'll have to scroll way out to see them, they're quite a bit away from the planet.

[KC_Daytona]

Thanks guys for the great replies !!!

[wallace18]

TMI:p LOL.