best GPS/ SATNAV?

[Theo]

They all tell you where you are, form factor and features are the primary basis of your choice.

I would add that there IS a difference among mapping services to which the GPS manufacturer subscribes. For example, Garmin uses NAVTEQ mapping services and Tom-Tom uses TeleAtlas mapping services. There can be some accuracy/update differences between those two, as well as how each designate roads as "seasonal" for routing purposes.

IMHO, I have never found a real problem with NAVTEQ maps; not so with TeleAtlas maps. However, the last comparison I did was about 3 years ago.

YMMV,

[marcopolo]

I've used a GPS on my bike since early 2005. I'd never consider a GPS that was not hard wired. I have a Garmin 276C now. While it does have a battery, I rarely use it this way, except in a motel room from time to time.

[bmwrider88]

I would add that there IS a difference among mapping services to which the GPS manufacturer subscribes. For example, Garmin uses NAVTEQ mapping services and Tom-Tom uses TeleAtlas mapping services. There can be some accuracy/update differences between those two, as well as how each designate roads as "seasonal" for routing purposes.

IMHO, I have never found a real problem with NAVTEQ maps; not so with TeleAtlas maps. However, the last comparison I did was about 3 years ago.

YMMV,

ah. so Tom-tom and Garmin use diffferent mapping services...
some of my English friends use Tom-tom GPS's- sometimes with horrendous result.
does TeleAtlas require frequent software upgrades?

what would the difference be? different satellites?

[Anyname]

As far as I know, the only GPS satellites available are those provided by the US Department of Defense.

The differences would likely be in the quality of the maps that turn the GPS coordinates into useful information.

[Theo]

[Apologies for the lack of brevity!]

There are two "sets" of GPS satellite systems orbiting Earth: the US have the DoD satelites (the Block I and II series), and Russia have the GLONASS satellites. The Chinese and EU are also building-out their Compass and Galileo systems (respectively).

The problem among mapping services is not the relationship between the satellites (in this case the US "set") and the ground, but in the mapping of the ground features in relationship to each other, the assignment of various road characteristics, and the effect these have on the routing algorithms that are used by the various GPSr manufacturers.

With apologies, a stretch of an analogy between a CD and a CD player can be used to illustrate the basic problem with variances in mapping data. Let's say that you have a audiophile-level CD (ok, now it's Blu-ray) player. The player is connected to other high-end gear and speakers. So, you have very accurate playback capabilities.

Now, you insert a brand new (DDD) CD into the player and marvel at the richness of the sound and the nuances heard in its reproduction by your system. Then, you insert a CD made by my son's garage band using a handheld dictation device and processed by my aging computer with so-so CD burner. You sit back and take in the whole gamut of the sound and realize that this could possible replace water-boarding as an interrogation technique. Same high-end playback gear, different result!

NAVTEQ and TeleAtlas both make their living by mapping the Earth using some pretty sophisticated techniques (I'm not a mapping expert!). However, sometimes they differ a bit in accuracy like missing roads, incorrect road surfaces, incorrect road speed limits, incorrect designation as a "seasonal" road, etc. All these road characteristics will have an affect on the (downstream) routing algorithms. For example, if a road is missing on one manufacturer's map data, you will never be routed over it and, possibly, be sent way out of your way by the routing algorithm. YOU can see that there is a road there when you look out over the handlebars -- but your mapping data knows nothing about it!

Another frequent routing problem occurs when the mapping data contains incorrect speed limit information for roads. If you want the shortest time between A and B, and there are two possible roads to be taken, the routing algorithm will route you over the road with the highest speed limit (all other road characteristics being equal). Road Alpha has a speed limit of 45 and Road Beta has a speed limit of 40. You will most likely be routed over Alpha. However, in the spring road Beta was repaved and the speed limit upped to 55. If the mapping data hasn't been updated since the prior fall, you will still be routed over Alpha, which does not produce the shortest time.

Other problems can be "hidden" and very frustrating. Three years ago, I experienced a Tom-Tom problem in the White Mountains of NH. This problem was not so much a mapping problem as an "interpretation" problem by the Tom-Tom software. There is a delicious seasonal road that runs between Rt. 302 in Bartlett, NH over a mountain range to the Kancamagus Hwy named Bear Notch Road. As you would expect, it is closed during winter. The summer I used the Tom-Tom, I could not get it to route me over Bear Notch because TeleAtlas has assigned it a "seasonal" status (characteristic) and the Tom-Tom routing algorithm just disregarded seasonal roads out-of-hand; even though it was in the middle of summer.

Theoretically, mapping services are constantly updating/correcting their data. They usually publish periodic updates for manufacturers allowing the data to be kept current -- but -- once they publish the data to manufacturers, it is up to the manufacturer to provide the data to us for download. If the manufacturer makes available the updated data only once yearly, good luck getting routed onto (or even finding) Bear Notch Rd or having the GPS route you over Road Beta!

I have always found the accuracy of the mapping data and the GPSr manufacturer's update frequency to be the key decision in buying a GPSr. That's why I have chosen NAVTEQ on a Garmin. I do stress, however, that I have not experienced a Tom-Tom GPSr since three years ago. Perhaps the TeleAtlas US maps have become more accurate, Tom-Tom routing algorithms are more sophisticated, and that mapping data updates have become more frequent.

YMMV,

[Omega Man]

More good stuff Theo Speaking of seasonal roads, I wonder where Hurricane MT. road between Conway and Rt 16 fit in on a GPS.

[Theo]

Yep! Looks like NAVTEQ has Hurricane Mtn Road:



That's on my "Must Ride" list this June!

I also like to use MapQuest on the web since they use the most recent NAVTEQ maps. I create my routes on MapQuest and download them to my Garmin Nuvi 550.

[tommcgee]

IMHO, I have never found a real problem with NAVTEQ maps; not so with TeleAtlas maps. However, the last comparison I did was about 3 years ago.

Maps are outdated as soon as someone puts a date on them. This is not to say they aren't still useful even 100 years later.

Google Earth uses TeleAtlas, among other sources. It'll prolly never happen, but would be cool if there was such a thing as real-time Google Earth.

And then there is Delorme's Maine Atlas and Gazetteer. It has far more info than the Delorme books for other states and if you're gonna ride in northern Maine, you need this book. No GPS has this kind of info. Lots of dirt roads are gated. The northern third of the state is mostly owned by lumber companies.

[Omega Man]

Yep! Looks like NAVTEQ has Hurricane Mtn Road:



That's on my "Must Ride" list this June!

I also like to use MapQuest on the web since they use the most recent NAVTEQ maps. I create my routes on MapQuest and download them to my Garmin Nuvi 550.

Neat! If you run it, I suggest a run over at an easy pace first as it is a wild spot. At a quick pace on the appropriate bike the front wheel will be the air a lot. It's a great road.

[tommcgee]

Yep! Looks like NAVTEQ has Hurricane Mtn Road:

Another perspective:

[Theo]

{snip}...It'll prolly never happen, but would be cool if there was such a thing as real-time Google Earth...{snip}.

Oops! Gotta go. Carol just got home in the MINI from the grocery store...


Re: Hurricane Mtn. Rd:

I always approach the first pass at an unknown mountain road like a petrified bat. Couple of times through, and I REALLY know my limits!

[Theo]

I think our prowess and hijacking threads is on abundant display today!

[Omega Man]

I think our prowess and hijacking threads is on abundant display today!

As far as I'm concerned yeah maybe on the fun road to ride but it also demonstrates how the IMG can be brought out if someone is route planning. The two versions, yours and Tom's, bring out more of the possibilities I was hoping for in this thread. Who knows maybe as things progress there could be suggestion of routing between two points and interested members could route it and see the difference between the systems along with an explanation of how the route came about.

[tommcgee]

As far as I'm concerned yeah maybe on the fun road to ride but it also demonstrates how the IMG can be brought out if someone is route planning. The two versions, yours and Tom's, bring out more of the possibilities I was hoping for in this thread.

I've used Google Earth a bunch of times to see if there were services at various exits. Being from New England, this is more of an issue for me riding in rural Canada, but I'd use it anywhere with sparse population.

[bmwrider88]

Theo,

your info on the satellites and mapping algorithms is great! the stereo playback analogy was spot-on.
too bad there isn't some grand crossover from all informational sources to create a single know-all mapping algorithm. probably some copyright or licensing infringements possible there?

gotta second the reference to DeLorme's state-by-state Gazetteers. simply marvelous if not bulky, cumbersome, and downright impossible for use while riding!

i know many folks' world turns on the dependence on the GPS, and i will eventually have one. but it seems there remains the definite advantage to the old-school and reasonably fail-safe method of writing the directions and mileages on a piece of paper and posting them in the tank-bag window?