Figure 66: Time Preferences

Many other GPS devices require you to to manually specify whether you're currently observing daylight savings time, so it's nice to see Garmin add an "Auto" option to let the GPS handle the time automatically (which makes sense really, since the GPS knows the EXACT time and your location).

Figure 67: Language Preferences

The nuvi 250 supports 30 different languages for voice, text, and keyboard settings. Note that the nuvi 250 doesn't have text-to-speech (the GPS doesn't announce actual street names. Instead, it says "left turn ahead", etc.), so the language settings only affect the on-screen text, generic voice prompts, and keyboard.

Figure 68: Display Preferences

The Display menu is home to the Color Mode, Screen Shot, and Brightness controls:

• Color Mode allows you to specify whether you want the GPS to use "Day" or "Night" mode, or automatically switch between the two depending on the time of day.
• Screen Shot allows you to capture screen shots of the nuvi and upload them to your PC
• Brightness allows you to adjust the screen brightness

Figure 69: Color Mode

Like other Garmin nuvi GPS units, the nuvi 250 can automatically switch between the standard, bright "Daytime" screen settings and the dimmer, darker "Nighttime" mode, shown below. When set to "Auto", the nuvi will automatically switch between the two display modes based on the time of day.

Some GPS unit's I've tested only change the map screen when night mode is enabled. Thankfully, the nuvi adjusts all the various screens for easy viewing in a dark car at night.

Figure 70: Daytime vs. Nighttime Color Mode

Figure 70 (above) shows a side-by-side comparison between Daytime and Nighttime mode on the Garmin nuvi 250. Both screen modes do an effective job of presenting the data in an easy-to-read way.

Figure 71: Setting the Brightness

Brightness controls are located on the Display menu. Brightness can be adjusted from 0 % to 100 %. Screen brightness on the nuvi 250 is good, but it's not as bright as the more expensive nuvi 600 series, or the Magellan Maestro.

Figure 72: Map Preferences

• Map Detail allows you to specify the map detail level
• Map View lets you set the map to 3D, Track Up, or North Up
• Vehicle allows you to change the vehicle icon (see section 16 in this review for details on using custom vehicle icons)

Figure 73: Map Detail

The Map Detail settings page allows you to set the map detail level. Adding map detail slows the map re-draw speed, and can also clutter the map, so I found the "Normal" setting typically the best setting.

18. Routing Engine Performance

One of the most critical components of any turn-by-turn GPS navigation system is the routing engine. Not surprisingly, it's also one of the most difficult and complex aspects for the manufacturer to get right (and it's the aspect of GPS navigation that is least well understood by consumers), as there are so many variables to consider. The nuvi 250 ships with NAVTEQ mapping data, so that is already a major plus. The two largest mapping data providers are NAVTEQ and TeleAtlas (for more detailed information on both NAVTEQ and TeleAtlas, check out "NAVTEQ vs. TeleAtlas, Which one is Better?"). NAVTEQ is more accurate and complete in North America, so it's preferable to buy a GPS that uses NAVTEQ rather than TeleAtlas (as of this writing).

However, there is a lot more to a routing engine than just the mapping data provider. How a given GPS will determine the "best" route is the result of not only the mapping data, but also how many additional data points, or attributes, are factored into the equation. For example, are certain roads closed after hours or on the weekend? What is the average rate of speed for a given road? Statistically speaking, more accidents happen when making left turns as opposed to right turns; is the GPS unit factoring that into the route? Each company takes all this data and compiles it in different ways. The number of attributes used varies depending on how much money the manufacturer is willing to spend on their mapping data.

How did the nuvi's routing engine stack up? Let's take a look: For the first routing test, I entered a starting address in New York City, and a destination address in Southbury, CT. I compared the route the nuvi calculated to that of the more expensive Garmin nuvi 660 (note that the Garmin nuvi 680 uses the same routing engine as the nuvi 660), the TomTom ONE, and Yahoo! Maps. I then ran subsequent tests comparing the nuvi 250's results to Magellan's Maestro, as well as the RoadMate 2200T.

Let's take a look at the results:

The nuvi 250 chose an identical route to the more expensive nuvi 660 -- not surprising given that both units use the same routing software. The TomTom ONE chose a slightly less efficient route, selecting a path that's 14 minutes longer than the nuvi's route (It's not totally fair to compare the nuvi 250 to the TomTom ONE, which sells for almost $200 less than the nuvi 250, but the point here is to show that there is more to routing than just mapping data. Both GPS units have the same roads available to choose from, yet the TomTom ONE chooses a different route. Why?) Yahoo! chooses an identical route to the nuvi, but estimates the arrival time at 6 minutes later than the nuvi. In fact, I found the nuvi was consistently too aggressive with it's estimated arrival time - I always had to exceed the posted speed limits to arrive at the destination by the nuvi's estimated arrival time. In the above test, the TomTom chose the "worst" route, and the nuvi and Yahoo! were identical from a routing perspective.

I also tested 3 more starting and destination addresses and got similar results. I also tested the nuvi 250 against the Magellan Maestro's routing engine, and found that although the Maestro has newer maps than the nuvi 250, Garmin's routing engine did a better job than Magellan's. In general, Garmin does the best job routing, Magellan is a close second place, and TomTom lags behind in third place.

Mapping data is a kind of dark art -- mapping and GPS companies are loathe to disclose their methods in any detail. From what I've been able to determine, NAVTEQ (who provides mapping data for almost every online map service, such as Google, Yahoo, MSN, etc.) provides more details about the roads than TeleAtlas does (TeleAtlas is used in the TomTom ONE). The additional mapping attributes, combined with the decisions a routing engine makes ultimately decides the route the GPS will take. For example, when calculating the estimated time of arrival, a routing engine might choose whether to discard the posted speed limit on a road and instead use the average speed of travel that NAVTEQ provides, or whether more accidents occur when making right turns than left turns, and decide to take a slightly longer, albeit safer, route. These are just some of the things that can affect how the GPS calculates the "best" route.

The nuvi has an excellent routing engine. That routing engine coupled with NAVTEQ mapping data makes the nuvi very good at its primary task: navigation.