14. Canceling A Route

Figure 89: Main Menu, While Navigating To A Destination

Tapping on the Menu button while navigating to an address brings up the Main Menu, shown above. From here, you can stop routing to the destination by tapping on Stop, or detour around a problem area by (such as a traffic jam or closed road) by tapping on Detour.

Including the Stop button on the Main Menu is a nice feature. I've tested a lot of GPS devices over the years, and have found that canceling a route can be a surprisingly difficult task. For example, looking at the menu on a TomTom GPS, it looks like there's no way to cancel the route at all (you can make this option appear by switching the TomTom to "Advanced" mode, but under the default menu there's simply no way to cancel the current route).

In my testing I found the detour function worked adequately, although there are no options for specifying how far you want to avoid the current problem, or ability to choose from a list of alternate routes, or exclude specific roads from the trip. But it does provide a quick and easy way to get off the current road if you run into a problem.

15. Where Am I? / Saving Your Current Location

Figure 90: Map Screen

Tapping on the vehicle icon on the map brings up Garmin's updated "Where Am I" screen, shown below. This is a great feature that provides one-touch access to your current street address (or closest valid street address), nearest intersection, and exact coordinates, and makes it easy to save your current location into the address book.

Figure 91: Where Am I / Save Current Location Screen

Garmin's well designed location screen also provides one-touch access to find nearby hospitals, police stations, and gas stations.

Tapping Save Location Saving your current location adds the current position to the nüvi's Address Book, and allows you to assign a name to the location.

Figure 92: Tools Menu

The Where Am I page can also be accessed by tapping Main Menu > Tools > Where Am I?

16. GPS Reception Performance

Figure 93: Garmin nüvi 660 vs. nüvi 755T GPS Signal Performance

Garmin no longer discloses which GPS chipset they use in their devices, and states that the 755T is equipped with a "high performance GPS receiver."

The nüvi 755T's chipset performed better than the SiRF StarIII equipped nüvi 660, both indoors and out.

Figure 94: nüvi 660 vs 265WT vs 755T

The nüvi 755T generally performed slightly better than the SiRF StarIII equipped nüvi 660, and much better than the nüvi 265WT, which was considerably less sensitive than either the 755T or the much older nüvi 660.

Figure 95: nüvi 660 vs 265WT vs 755T

Testing revealed that the more expensive 7x5 series is using a higher performance GPS receiver than the 265WT.

Figure 96: nüvi 660 vs 265WT vs 755T

Indoor, outdoor, and in-vehicle test results consistently showed the nüvi 755T's GPS receiver is more sensitive than either the 265WT's or nüvi 660's.

17. Routing Engine Performance

All the bells and whistles aside, what really matters on any GPS is its ability to intelligently get you from point A to B.

The most common complaint I hear about any given GPS system is that "it took me on a wild goose chase", followed closely by: "that was definitely not the best way to go."

How well or poorly a GPS is able to route you to your destination is a function of two critical components: the routing engine, and the quality of the maps installed on the device. The routing engine is the internal logic the GPS uses to figure out the best route to take. Many people falsely assume that simply having the same maps installed on two different GPS devices will result in the same routing choices. Not so, as there is a great deal of math, personal preferences, and economics going on behind the scenes when your GPS calculates the "best" route.

Not surprisingly, routing engine performance is one of the most complex aspects of any GPS system, and is generally not well understood by consumers. In truth, routing quality is probably the single most important aspect of any turn-by-turn GPS device, and should be a determining factor when purchasing a GPS.

The two largest mapping data providers are NAVTEQ and Tele Atlas . NAVTEQ used to have the advantage in mapping quality in North America. However, Tele Atlas has improved its US database in recent years, and both companies are now roughly equal in quality. The mapping provider shouldn't be a determining factor in routing quality, as both NAVTEQ and Tele Atlas are capable of providing excellent maps to GPS manufacturers. That said, it's important to understand that both NAVTEQ and Tele Atlas sell many different levels of maps, ranging from inexpensive data sets that only contain basic information to more expensive offerings that contain much more detailed information.

For example, is a road closed to commercial traffic? Does a given road close at night? Are there weight restrictions on a certain highway. All of these are examples of additional information available to GPS manufacturers, at a cost, to factor into the GPS' routing logic. The number of attributes used varies depending on how much money the manufacturer is willing to spend on their mapping data. For example, a full NAVTEQ map database that includes all available attributes can cost the manufacturer twice as much as a basic set of attributes.

Even when two different devices are provided identical map sets, each manufacturer makes numerous decisions that impact routing. For example, statistically speaking, making left turns is more dangerous than right turns. Some devices will favor right turns over left turns, even at the expense of additional travel time.

When testing routing logic, I'm looking for routing logic that can make intelligent decisions about which roads to take. I'm not looking exclusively for the shortest distance, as often a slightly longer distance will be much less trafficked and result in a shorter overall drive time. I'm also looking to see if a device is sophisticated enough to understand that at 5pm on Friday, many highways are parking lots, and surface roads should be favored. Also important is the GPS's ability to gracefully handle missed turns, and quickly re-route.

Test #1: Actual Road Test

To test the nüvi 755T's routing engine, I drove over 300 miles on a road trip from New York to Maine, stopping off in Boston along the way, and back again.

I also brought a Magellan Maestro 4250 along, as well as a TomTom GO 930T, and compared the routing decisions, ETA accuracy, traffic alerts, missed turn re-routing, and GPS signal reception quality on all units.

The nüvi 755T performed exceptionally well in real-world driving tests. GPS signal performance was solid, and the 755T had no problem maintaining a strong signal when driving behind tall buildings or through short tunnels. The Magellan Maestro and TomTom GO 930 performed equally well from a GPS signal strength perspective. All three units acquired their position quickly, and maintained map tracking the entire time.

However, the nüvi 755T was better at handling missed turns than either the TomTom or the Magellan. When I would miss a turn, the 755T would quickly realize the turn had been missed, and would plot a new course based on my current heading. The TomTom and Magellan would also realized I had missed a turn, and "re-calculated", but they favored lengthy U-turns or backtracking instead of truly re-calculating based on my new heading.

For example, when I missed a highway exit on I-95, the nüvi 755T quickly re-calculated, allowing me to continue on towards my destination, and found another route that was only 2 minutes longer. By contrast, both the Magellan and the TomTom wanted me to exit at the next opportunity, get back on the highway going in the opposite direction, exit again, get back on the highway, and take the originally planned exit. In other words, a 10 minute u-turn.

Out of the box, the nüvi 755T had the most accurate ETA times. Even on a 300+ mile trip, my actual arrival time was within 10 minutes of the nüvi's original estimate. Magellan's Maestro was also very good at predicting the ETA. TomTom's ETA fluctuated significantly during driving. If I drove 80 MPH for even 2 minutes, TomTom would adjust the ETA drastically and shorten the estimated drive time. If I sat in slow traffic for a minute or two, TomTom's estimate would jump up.

Garmin's nüvi learns driving behavior as you use it, and, over time, its ETA predictions become more accurate. TomTom's 930T has a similar learning feature called IQ Routes that allows the GPS to store historical driving pattern information and adjust routes and ETA's accordingly. Magellan does not yet have the capacity to learn driving behavior over time.

From a pure routing perspective, the Magellan and Garmin were roughly equal, though I tended to prefer Garmin's traffic notifications and map screen. TomTom's GO 930T had an uncanny knack for routing me straight into traffic jams, and seemed to have no awareness that I-95 would likely be slow moving on a Friday during rush hour.

I suspect TomTom's routes might have improved over time, thanks to the GO 930T's innovative IQ Routes feature.

All three units were competent, and successfully guided me to my destination. However, I found Garmin's nüvi 755T the most comforting to use, and the most consistent performer in the group.

Test #2: Simulated Routes

I also performed a series of bench-tests, entering three different trips of varying distance in three different regions of the United States, and comparing the nüvi's results to the Magellan Maestro 4250, and TomTom GO 930T. All three test units had the latest available maps installed, and the most current firmware as of this writing.

Our first test took us along the Northeast, starting in Southbury, CT and ending in New York City:

Magellan's Maestro 4250 and Garmin's nüvi 755T choose essentially identical routes. The Garmin nüvi is slightly more aggressive in its estimated drive time, but both GPS units do a good job routing, both announce which side of the street our destination is on, and both ensure that we arrive with the destination on our right.

TomTom's GO 930T has us arriving with the destination address on the opposite (left) side of the street. We would then either have to make an illegal U-turn or go around the block to arrive at 135 Central Park West on our right. TomTom also reports distances in yards instead of feet, which is less commonly used here in the United States.

Yahoo! Maps (not shown in the table above) chooses a route identical to the Maestro 4250 and Garmin 755T, but estimates the trip will take 3 minutes longer than Garmin estimates (1 hour 22 minutes). Google Maps also chooses the same route as the Garmin nüvi and Magellan Maestro.

Winner of Test #1: It's a tie between the Magellan Maestro 4250 and nüvi 755T.

The first test was approximately 80 miles in length and took us from Connecticut to New York City.

For the second test, I started out at Fry's Electronics in San Jose, California and entered a destination address at 300 Grove Street in San Francisco (about 46 miles in distance):

Again the Magellan Maestro and Garmin nüvi choose virtually identical routes, and the TomTom GO 930T chooses the least efficient route. While Magellan and Garmin both route us along the 101 highway from San Jose to San Francisco, TomTom's GO 930T instead routes us along highway 880 North to 80 West -- an odd choice that adds around 4 miles (~6 minutes) to the journey, assuming there's no traffic 880 (which there usually is). Even worse, TomTom again has us arriving on the wrong side of the street, with our destination address on the left.

Both the Magellan Maestro and the Garmin nüvi arrive with our destination address on the right side of the street, and both units announce what side of the street our destination is on.

Winner of Test #2: It's a tie between the Maestro 4250 and nüvi 755T.

For the third test, I chose a short, 3-mile trip from Beacon Street in Boston to Cambridge, Massachusetts:

Magellan's Maestro just slightly edged out Garmin's nüvi 755T in this test, and TomTom's GO 930T again comes in third.

TomTom's GO 930T unit performed least well in all three routing engine bench tests, producing the longest routes in all three tests, and putting us on the wrong side of the street at our destination address.

I've received many questions asking why it's important to arrive on the right side of the street. In more rural areas, it likely won't make much difference if you arrive with your destination on the right or left. However, when driving in cities along wide avenues, such as in New York City, it's very important to arrive on the same side of the street as your destination. Otherwise you'll need to make an illegal U-turn or drive around the block.

Regarding the estimated drive times, some readers have commented that these tests unfairly penalize TomTom for more conservatively estimating the drive time, and reward Garmin for unrealistically aggressive (short) drive times. I disagree with these assertions, as I have actually driven many routes with all three devices connected and compared the routing choices made by each. .