Using a GPS for fuel economy

[ketel0ne]

Please list some uses and what types of units you guys are using of GPS'.

I am looking to map my commute with elevations, speed and distances in realtime.

[Wazabi Owner]

I have a Garmin Nuvi and a Tom Tom. I like the Nuvi best. Neither tell altitude but the Nuvi has a "max speed", "average speed", "average moving speed", "moving time" and a few other items on one screen - I like that option a lot.

I had a Zire 72 with a Delorme Blue Logger - both ended up having battery issues in the end.

As far as altitude goes, I had a laptop with Delorme software and GPS - IMO 6 years ago it was superior to the Garmin or Tom today for detail/altitude etc. The new GPS are great for finding stores etc though, VERY quick to find a nearby store.

Hope that helped a little.

[maximilian]

I just got a TomTom One, 3rd generation. It has the max speed feature as well which is a nice compromise between "plan shortest" and "plan fastest" since 52 is about what I average on the highway.

[Jay2TheRescue]

I have my TomTom alert me if a restaurant that was featured on Diners, Drive-ins, & Dives is on my route...

[maximilian]

Nifty! A lot of the POI lists are obsolete, unfortunately. This is a real pain since I live in the sticks, so it shows the nearest Lowes as 200 miles away and stuff like that.

[bobc455]

I have a Nuvi. I seldom use it - it mostly stays tucked away. But when I am going to someplace new or unfamiliar, I pull it out. (It seems silly to mount the thing on my windshield for the routes I drive every single day, too much clutter and I have no desire to be a blatant gadget freak.)

I also use it when I am going between two points that I know, but I just don't know the best route. For example I know where my mother lives and where my brother lives, but I might not know the best route between their houses. Since I can utilize the GPS to figure an efficient route, that saves me gas when compared to taking a not-so-optimum route.

I will also occasionally use it to double-check the routes that I take every day. For example it did give me an alternative route from the gym to work that I'd never have considered, which is actually shorter & quicker than my old route (hence saving me some gas). The only other time I will use it is to calculate an ETA - then I turn it back off and put it away.

My GPS was a gift - I would not have bought it on my own. I know I would NEVER pay back the $199 (or whatever) on gas. I *might* have saved $5 in gas in the time I've owned it.

-BC

[maximilian]

I got my GPS mostly so I could calibrate my speedometer for a coast down test. I also really hate driving in city traffic while juggling directions. Refurbished TomToms have gotten so cheap I found it hard to resist finally getting one. Half the price of what I paid when I got one as a gift fro a friend who gets car sick when trying to read and drive (and is therefore navigationally challenged).

[Lug_Nut]

Originally Posted by Wazabi Owner

I have a Garmin Nuvi and a Tom Tom. I like the Nuvi best. Neither tell altitude but the Nuvi has a "max speed", "average speed", "average moving speed", "moving time" and a few other items on one screen - I like that option a lot.

My Nuvi 350 has altitude. I knew it did last night when I was on line, but damned if I could find the screen then.
Today's a fresh start.
On the 350: "Where to?", "My Locations", "My Current Location". This brings up present coordinates and altitude.

<p.s.>Based on that information on my level of knowledge (or lack thereof) of the unit's capabilities, it should come as no surprise that I have absolutely no idea if that information can be logged and downloaded.<end p.s.>

[bobc455]

Actually all GPSs compute altitude (they compute position 3-dimensionally), but many don't show it. Your average soccer mom probably doesn't even know what altidute is...

One more point of interest - your GPS is actually the most accurate clock you own...

-Bob C.

[JanGeo]

I have an old Garmin GPSIII+ which does display altitude as well as tracks where you have been and time and speed for each segment of the trip. Great when you get into a crash because it records the exact time and location. I use the altitude once in a while when I see my mileage dropping on trips and can't figure out exactly if I am going up hill or not - it really shows where the gas goes in those situations. I also have a TomTom 710 with out of date maps even when purchased new and within the first year of free updates got no new maps even though they were out of date to start with. Seems to be a reoccuring charge marketing ploy . . . It has the Mount Hope Bridge as a toll bridge which is has not been in about a decade. Other than that it is great for having all the roads on it where as my Garmin only can hold maps for a few selected areas at a time and they have to be loaded and removed as needed because of limited memory.

[maximilian]

My TomTom allows me to add map corrections and share them with others. Yesterday I changed a curve that had one end blocked off. Odd, since the same basic change done elsewhere in the same town around the same time was in the maps.

It definitely has some weird stuff, design wise. I can't set it to not quiz me every time as to whether or not to avoid unpaved roads. I live off of one, so every single time it pesters me. I also can't make it lock the owner's information. It can take a password, but then I have to enter it each and every time it starts up. I just want to require a code to change the info!

[JanGeo]

Sounds like MapShare which comes at an addition cost as I recall.

[maximilian]

Yes, MapShare. Good news is it's free. I assumed it wasn't too but I checked into it.

[theholycow]

+1 on the GPS being the best clock.

Here's how GPS technology works (very simplified): The satellites all broadcast the time with very fine resolution, and very accurately. Because that broadcast moves only as fast as light, there is a very tiny difference between each satellite's broadcast in how long it takes to reach you. Your GPS compares that and calculates how long it took to arrive from each of 4 or more satellites, and therefore its distance from each of those satellites. It figures its position based on that.

Therefore, the time has to be perfectly synchronized and measured in each satellite and in the GPS receiver, which assures you that it's got the best time.

That also means that if your GPS is having trouble acquiring its position, you should make sure it's got the time set correctly (or nearly so); that helps it make sense of the satellite signals more quickly.

[theholycow]

Originally Posted by bobc455

I will also occasionally use it to double-check the routes that I take every day. For example it did give me an alternative route from the gym to work that I'd never have considered, which is actually shorter & quicker than my old route (hence saving me some gas).

I've found that Google Maps (not Google Earth) by far the best for this purpose. I used to like Microsoft Streets & Trips best, but now with Google Maps you can drag your route to your preferred roads. Especially combined with satellite imagery, this makes it the perfect tool for detailed fine-tuning of a daily route.

[maximilian]

Any way to set max speed in Google Maps? If there is I've been missing it.

[theholycow]

No, setting different speeds for different types of roads was one of the things I liked about Streets & Trips, but with Google Maps ability to graphically manipulate routes there's no need for it.

[maximilian]

Originally Posted by theholycow

+1 on the GPS being the best clock.

I always assumed GPS units were just digital clocks updated from an atomic clock every so often. Is that true? The satellites have atomic clocks I know, but clearly the unit doesn't!

[theholycow]

The GPS time is updated from the satellites every second. That's how it knows where you are.

[maximilian]

Now that's interesting. Since there are delays in the communication from the satellites, and it also relies on those delays to compute the position, I wonder how they accurately figure out exactly what to set the time to? Pretty easy if you know already almost exactly your location or the time I guess.

[JanGeo]

Time is all relative so it doesn't matter . . . remember it takes a nano second for the radio signal (and light) to travel 1 foot so depending upon where you are and how it compensates you are not off more than a fraction of a second and even if you were it doesn't matter since even a phone call would take more that that to travel any distance to someone else in case you were late by a second or two.

Mapshare is free but I can't seem to get my unit to work with their website - I think it was only free for the first year but it looks like it is free now . . . only it's broken.

[maximilian]

Gotcha. The unit doesn't need accurate time, it just gets it as a side effect. Never looked into the GPS math before. Intersection point of spheres, basically. I checked and my TomTom was off by four minutes today (compared to my computer which I double checked against an atomic clock). Not that it matters at all, but I was surprised.

[Jay2TheRescue]

Time is part of the equation in plotting your location. at different times the satellites are in different portions of the sky. Knowing what time it is is critical to knowing where you are. On my old GPS when they changed the daylight savings time the unit stayed on standard time, and it was tracking me about 200 yards north of my actual position. If I wasn't traveling east/west at the time I probably wouldn't have noticed. I was showing following the path of the road, but a few hundred yards off to the side. I pulled over, and made a manual correction for daylight savings time and the GPS was accurate again.

EDIT: I found when I had discussed it...

http://forums.wirelessadvisor.com/th...tml#post438268

[theholycow]

Originally Posted by maximilian

my TomTom was off by four minutes today (compared to my computer which I double checked against an atomic clock). Not that it matters at all, but I was surprised.

I'm surprised too. That doesn't make sense. Did your TomTom have a good fix on your location?

[DarbyWalters]

Garmin Street Pilot III ... does all I need

[maximilian]

Which is...?

[JanGeo]

hey hey hey lets not ask those personal questions here - this is a "G" rated family site.
I don't think the error in position was caused by the time change more likely a poor sync which adjusted after you stopped. Mine shows the position error amount by a circle around my position which grows and shrinks depending upon atmospheric conditions which affects the speed of the sat signals slightly.

[maximilian]

Now that is a cool feature! Small position errors in mine make the car image jerk every so often when driving (mostly in turns). Looks like the driver is drunk.

[JanGeo]

There is also a feature that allows you to sample a fixed point for as long as you want to get a more accurate positioin fix and that can put you within a foot or so with consistant repeat visits to that same spot years later.

[Lug_Nut]

Originally Posted by maximilian

Now that is a cool feature! Small position errors in mine make the car image jerk every so often when driving (mostly in turns). Looks like the driver is drunk.

Mine too! But it's weird that it only happens when I actively watch the track while trying to negotiate a turn. When I watch the road instead, my passenger says it tracks smoothly....