Finding Destinations
Arguably the most important part of a navigation application is the ability to locate your destination easily. No matter how good the routing and navigation is unless you can locate your destination then the rest is rather a waste of time...
Fortunately Garmin Mobile for Blackberry has one of the best destination finders I have used to date. At first the Garmin Mobile system is a little daunting, but with use it becomes second nature and pretty easy and intuitive to find places.
In the UK navigating to a destination is easy. The postcode alone is sufficient to put you close enough to see your destination.
In the US though a zipcode can cover a huge area. This is totally unsuitable for finding an exact location. Worse than that you cant even use a road name!! The one outside where I was staying was a few hundred miles long and changed its name a few times. In the 20 miles between Davenport and Kissimmee it went through at least 4 cities.
Often you may know the road and house number but not the city. Garmin have catered for this by providing a method of address location using State, House Number and Street Name. This then searches the database and shows all the cities matching that criteria. Of course you then have the problem of which city you should be going too, but most addresses should be pretty obvious.
Once you have found your destination there are a number of things you can do other than set it as the point to navigate to. You can then select one of the options and view it on a map. You can also look for Points Of Interest (POIs) nearby.
I find this lookup feature really usefull. Often I want to see what is around a particular location. This is ideal for that sort of search. I must admit that I tend to use POIs much more when I am in the US than anywhere else. I suppose it is a different mode and style of driving.
Dont expect all POIs to be in the database though. I was in Millenia Mall in Florida standing right outside an Apple store and did a search for Apple. The closest result was "Big Apple Transportation" 2.9 miles away, and not a single Apple store was in the listings.
Routing Calculations
The next most important thing after you have located your destination is to get there... This is where the routing engine calculations com into play. The routing calculations for Garmin Mobile are done over the air on the Garmin Server. When you go off the designated route Garmin Mobile will dynamicaly request a route re-calculation to get you back on track.
There are a number of settings that can be made to affect the sort of route that will be created:
Avoidances: There are a number of selections that can be made to be considered when calculating the route: Traffic; U-Turns; Highways; Unpaved Roads; Toll Roads and Ferries. Selecting one or more of these will alter the routing calculations
Route Preference: Here you can select either shorter distance or faster time. The time calculation is based on the posted speed of the roads in the route.
Vehicle Type: There are a number of different classes of vehicle that the route can be optimised for. These are mainly due to different access capabilities. For instance a pedestrian can walk on a footpath, but not down a highway, and vice versa for a car. Some roads are only open to public transport etc.
Routing calculations are processed on the Garmin server then the results sent to the BlackBerry. This allows the system to leverage the computational power of the large server releasing the BlackBerry for the display of the returned information.
Now the interesting thing about routing is that you can always find a better route than a machine for an area that you know well. You have local knowledge and know when a particular intersection is busy, or that the sequence of a particular set of lights means you may wait 5 minutes or more before turning, but the Routing Server doesnt have that level of detail (yet!). The main question to ask from a route is: Does it get from A to B in a reasonable amount of time? 99% of the time the answer is going to be Yes!
Most of the routes we drove in Florida were pretty obvious ones. There are a system of main highways which when flowing properly will always be faster than taking back roads. Backroads become faster when the highways are blocked or slow. In theory the Garmin Mobile system should take into consideration traffic problems. I suspect that the one I nearly got caught up in had not managed to be transmitted to the server before I hit the tail of the log jam.
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I tried at the time to install it but ran out of time before having to return home to the UK. OK I thought no problem I will install it back home. 
The map data is supplied by Navteq one of the two main global suppiers of digital map data. This is stored on a central server and supplied to the BlackBerry over the air as needed.
