Garmin Maps - Part One: The Basics
Ken in Regina
Part One: The Basics

In order to understand Garmin's map products you first need a little bit of Garmin history. Garmin has been making navigation devices for many years. Devices for personal, handheld navigation. Navigation devices that are installed in cars, boats and airplanes. Devices which use GPS signals to determine your location and the direction and speed of your movement.

These devices require maps loaded into them to be useful to you for navigation.

It is important to realize that Garmin has been making these navigation devices for a long, long time. Since long before small, inexpensive, high-capacity memory cards were available and so long ago that built-in memory was also quite expensive.

Until relatively recently it simply wasn't possible to load an entire continent or even very large regions into a navigation device because the memory to do so was just too expensive.

So Garmin's map products are designed around the problem of how to give the customer an entire (very large) country or even an entire continent in a single product but be able to load only portions of it into the customer's navigation device. Someone in Europe might have enough memory in their navigation device to only hold one country. Someone in North America might only be able to fit a few states. But in order to travel around and take longer trips they need to be able to select those parts of the countries or continent that they load. They need to be able to customize what they load for a particular trip.

Garmin has created two types of maps to accomodate this. First there are basemaps. These basemaps contain only major roads (freeways and highways) in, and between, major population centres (medium and large cities). This allows for navigation across large distances without taking up a lot of memory, as long as you are planning to travel on the main roads.

Second, there are detail maps. These maps are the ones that matter when you want to navigate within a population centre (city and town). They contain details of the surface streets and smaller highways that are not in the basemaps. They also contain searchable databases of city and town names, addresses, and points of interest (POI). Points of interest might include geographical features, parks, hospitals, police stations, and various commercial interests (donut shops, dress shops, hotels, gas stations, etc.).

With all that data available and only a small amount of memory available in the navigation device Garmin had to come up with a method to allow their customers to select only those parts of the map coverage area that they need for the trip and load only those areas to the navigation device.

So they came up with the products that they refer to as MapSource products. These are map products that contain all the necessary details for a very large area; a large country or a complete continent. These products come under brand names like Metroguide Europe and City Navigator North America. They are shipped on multiple CDs or a DVD. They contain a program called MapSource and all the necessary details for navigation in the very large region they cover.

The first, and most important, thing to know about these map products is that the CD or DVD does not contain a single map covering the entire region (Europe, Australia, North America). They contain dozens or hundreds of much smaller maps covering only small segments of the region. In areas of low population, like in the western United States or western Canada, these segments might cover a large amount of land. In areas of high population, like New York City or Los Angeles, it might require many segments just to cover the one city.

The size of a segment does not only depend on how many streets there are. It also depends on how many addresses and points of interest are covered in that area. In a densely populated city there will be a very large number of addresses and points of interest that need to be included in the segment file, along with the streets and roads.

The MapSource program that comes on the disk with all those map segments is the tool you use to manage the maps for the region that came on the CDs or DVD. MapSource allows you to view the entire region as a single map and do all of the travel planning things you need, like planning and saving routes, searching for towns or addresses or points of interest. But the most important thing it does is allow you to select the map segments you need for your trip and load them into the navigation device.

MapSource does not just load the individual segments to the navigation device. The Garmin navigation devices normally only work with two files. One file is the basemap file. This is usually named gmapbmap.img on the navigation device. The other file is usually named gmapsupp.img. This is known as the "detail map" because it contains all the segments of the map details that you have selected in MapSource. When you have selected the map segments you need and ask MapSource to transfer them to the navigation device, MapSource first compiles them into a single gmapsupp.img file and then transfers them to the navigation device.

Now the navigation device has a combination of the basemap for navigation between major cities over major highways plus all the many details for just those segments you have selected. You are ready to use one of Garmin's many navigation devices to take a trip.

#### End Part One ####
laptopgpsworld.com About