GPS Systems as of 2005

A lot of changes have occurred since my last article about GPS receivers (GPSr's) so I've decided that it's time for an update. I recommend that you read the first article to understand the basics of what GPS is and how it works. Then read this article which will focus on features available on current systems.

Selective Availability

WAAS

• GPS (SA on): 100 metres
• GPS (SA off): 15 metres
• GPS + DGPS correction: 3-5 metres
• GPS + WAAS correction: less than 3 metres

The downside with WAAS is that it is correctly operable only in North America, and since it was originally designed to improve GPSr positioning for aircraft uses, those of us in the more northern latitudes will have problems picking up a signal from the WAAS satellites since they might be over the horizon. (This isn't usually a problem for aircraft since they operate at such high altitudes.)

The recreational uses, including Geocaching, 15 metre accuracy is plenty. So don't pay extra just to get WAAS capability unless you have a very specific need for that kind of accuracy, and make sure you will be able to get the WAAS signal in the area where you are expecting to use it.

Auto-routing

Having an auto-routing GPSr doesn't mean you can auto-route with it. You will also require maps that support auto-routing. Some GPSr's come packaged with such maps, while others require that you buy it separately. Using auto-routing maps on a non-auto-routing GPSr, or non-auto-routing maps on an auto-routing GPSr will result in the same thing: NO AUTO-ROUTING.

As an added bonus, most auto-routing map databases also contain huge amounts of waypoint listings such as emergency services, auto services, food and restaurants, attractions, entertainment, hotels, campsites, retail stores, and geographic points of interest (eg: Hell's Gate in the Fraser Canyon). This is very useful if you're travelling to another city and are looking for, say, the nearest Time Horton's, or Canadian Tire, or Chevron. On Garmin's CitySelect North America, I found the Capilano Suspension Bridge, the Tomahawk Restaurant, and North Shore Off-road. Yes, there are bound to be some locations that aren't listed, but the majority I have looked for are in there. Besides the map coordinates, the listing also includes the street address AND phone number.

To give you an idea of what auto-routing is about, here are some photos. They are from a Garmin 76C running CitySelect North America version 6.0.

Here's a high-level map view of the New Westminster area.	And here's a close-up view, showing the street level detail.	From that New Westminster location, I have pressed the Find button. The Find menu has popped up and I am about to choose to search for a restaurant.
The default screen that popped up listed the nearest points of interest (or waypoints) for the chosen category. In this case, it listed the restaurants and food vendors nearest to my location in New Westminster. Tomahawk's is in North Vancouver so I chose the menu to find a restaurant by name.	Next, I started typing in letters to spell out Tomahawk. For each letter I typed, the list of choices got pared down to only those names that matched what I typed. In this shot, it has been narrowed down enough that Tomahawk Barbeque is displayed near the top of the list.	Clicking on Tomahawk Barbeque brought up the detail page for the restaurant.
Clicking on Map will display the Tomahawk location on a map (which you can zoom in and out on, as needed).	Clicking on Go To will cause the GPSr to start calculating a route to get from my location in New Westminster to Tomahawk's in North Vancouver.	Once the route was calculated, the GPSr displayed the route (indicated in pink).
As I approached an intersection, the map display automatically changed to a track up format (ie: the top of the screen was my direction of travel), the map was zoomed in to show the turn details, and the GPSr sounded an alarm to warn me of an upcoming turn. It also displays the distance from the turn and the estimated time of arrival at the turn (376 metres and 27 seconds).

Auto-routing will cost you more money for two reasons: 1) the GPSr needs more memory to contain all that street level detail and 2) the source for the map data (eg: Garmin buys their map data from NavTeq) is more expensive due to the detail and accuracy requirements. You will also want to update your maps every few years since streets do change over time (more so than highways). I also recommend buying a GPSr with as large a screen as you can afford, and definitely choose colour, because a cluttered map is very difficult to read using a monochrome screen.

If you're wondering why auto-routing is worth it over simply having a mapping GPSr, then consider this:

1. The map accuracy and detail is better on auto-routing maps.
2. The small display screen on a GPSr makes it very difficult to plot out your route because to do so, you need to be able to see your location in the context of where you want to go, and how you can get there. This combination of context and detail means you need a large paper map, or a large screen (laptop size) to display the map. Auto-routing gets around this problem by plotting out the route for you. Therefore, you don't need the context view which means you don't need a large screen.
3. Because of point #2, you will usually need a paper map if you're trying to find your way around using a mapping GPS.

If you think auto-routing GPSr's and map software are expensive, have a look at the dedicated auto navigation systems at your local car stereo shop or car dealership. Hand-held auto-routing GPS units are a STEAL compared to what a dedicated in-car system sells for.

But you do you really need auto-routing? Basically, if you want to use your GPS to find out where you are, then mapping is good enough. If you use your GPS to figure out how to get somewhere, auto-routing is a must-have.

Uploadable Maps

Map Storage (GPSr Memory)

If you buy a GPSr that has only built-in memory, you need to consider your requirements. You should also visit the manufacturers' websites to figure out how much of an area the GPSr you're considering can fit into its memory. This depends on the GPSr, the map product you think you will use, and the area you want to fit into memory. As an example, my Garmin 76C has about 115MB of map memory, and I can store street level, auto-routing maps for all of British Columbia, Washington, and Oregon, as well as Enhanced Canadian Basemap data for all of British Columbia, with a little bit of space left over. For me, that is probably all I'll ever need unless I go on a flight or a long driving trip. But for daily use and weekend recreational use, I doubt I will go farther than that. In contrast, my Garmin III+ which had 1.44MB of map memory, could hold only street-level maps (non-auto-routing) for the lower mainland area, extending as far east as the Fraser Valley.

Of course, if you're sticking with major highways for most of your trip, you don't necessarily need street-level detail for all areas. For instance, if I'm driving from Vancouver down to the Oregon Dunes, I don't really need detailed maps for all of Washington. The 76C comes with a set of built-in base maps which don't take up any of the user-uploadable memory. These base maps cover all of the Americas (Alaska down to South America) with particularly good highway detail for Canada and the United States. So I could just upload Oregon detail maps and rely on the base maps for the areas in Washington where I know I'll be on the major highways or city streets. And that's exactly what I did on my trip to Oregon, using my III+ and its 1.44MB of memory. So, although lots of memory is nice to have, it's very likely that you don't need huge gobs of it. For an auto-routing GPS, I could probably get by with around 64MB which is about half of what I have now. But that's just me. Someone else might need more...or less.

PDAs and GPS

Geocaching

Here's an example of the geocaching features of the Garmin 76C:

We use the main Find menu and then choose to search for Geocaches.	A list of geocache waypoints is displayed where we can choose the one we want to find.	After clicking on a geocache waypoint, its details are displayed, much like the restaurant's details were.
Clicking on Data doesn't bring up a particularly useful data screen.	Clicking on Go To displayed all the data needed to find my way to the cache. I could also have used the map display to see a route and my position in relation to the cache's position as well.	When I clicked on Found, the cache's waypoint is set to found, the date/time of the find is stored in the GPSr's calendar program, and the next nearest cache is displayed. Notice that the next cache's direction and distance is also displayed.

Built-in Altimeters and Compasses

External Antennas