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 AvailabilityWithout a doubt, the biggest news since my last article was the de-activation of Selective Availability (SA) in May of 2000. When the US government turned-off SA, the average accuracy of civilian GPS receivers increased from +/- 100 metres to +/- 15 metres. That's a huge improvement and it cost GPS users nothing to achieve. SA might be turned on again if it is deemed necessary to US security, but that probably won't happen, or it if does, it won't last for long. In the meantime, we can enjoy getting 15 metre accuracy from our GPSr's.
WAASMost GPSr's, including very inexpensive units, now have WAAS built-in. WAAS (Wide Area Augmentation System) is similar to DGPS in that it uses an additional signal source that provides correction data to further improve the unit's accuracy. In this case, the correction data is produced by a series of ground stations. That data is then sent to satellites in geosynchronous orbit over the equator, and then broadcast to GPSr's. This is a much more wide-reaching system than DGPS, which relies on relatively short range FM transmitting stations. It also differs from DGPS in that you do not need to connect a DGPS receiver to your GPSr. The WAAS signal can read read by the GPS receiver. Typically, a WAAS-enabled GPSr will dedicate two of its twelve channels to reading the WAAS satellites and leave the other ten to receive GPS signals. Here's what WAAS gives you as compared to other GPSr configurations:
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-routingOnce only available in a handful of expensive GPSr's, auto-routing is now a very common and affordable feature. Auto-routing requires a GPSr that supports the use of uploadable maps (a few of these units have the maps already uploaded from the manufacturer). Where these auto-routing maps differ from earlier mapping GPSr's, is that auto-routing maps contain street-level details. This detail is needed because auto-routing calculates actual routes and provides turn-by-turn directions. These turn-by-turn directions are displayed graphically, as well as textually. Some units will alert you to upcoming turns by sounding buzzers, while others will actually speak the directions using a simulated voice. Auto-routing makes it easy for a person to navigate in an unknown city (or province, for that matter) without requiring the assistance of a passenger to read the map. And if you miss your turn, most units will automatically re-calculate the route. I tested my Garmin 76C and found that the routes it chose were the same or as good as the routes I would have chosen myself. I've also used a Garmin Street Pilot 2610 in the Boston area for a week and never had to resort to a paper map to find my way around.
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.
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:
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 MapsAny GPSr that supports uploadable maps uses vector-based maps that are in a proprietary format. In other words, you can take scanned maps (ie: like the ones you use in Fugawi or OziExplorer) and upload them into your GPSr. Fortunately, that situation is changing. There are third-party tools that will allow you to create your own vector-based maps and upload them into your Garmin or Eagle/Lowrance. I don't know if there is a tool to create maps for Magellan GPSr's, although I wouldn't be surprised if there were. Creating these maps is time-intensive and it would help a great deal if you were comfortable with mucking around with software, although no programming is required.
Map Storage (GPSr Memory)These detailed maps are bigger and therefore require more space to fit in a GPSr. All mapping GPSr's have some form of built-in memory or support external, plug-in data cards. The latter is the ideal solution but not all GPSr's support these feature. Magellan is your best bet if this is what you are looking for, since only the higher end (ie: expensive) Garmin units provide this and they are usually aviation- or automotive-specific. Magellan makes automotive AND outdoor use GPSr's that support external data cards. Data cards are the idea solution because their price per MB is very economical and you can choose just how much memory you want in your GPSr. If you are going on a trip that will cover a large area, you can pre-load all your maps onto multiple cards (or buy one, very large card). This way, you won't need to rely on the availability of a computer to load maps onto your GPSr part-way through your trip.
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 GPSA handheld solution to using scanned maps and GPS does exist. Just use a PDA like a Palm or PocketPC in conjunction with a small GPSr and a mapping program like Fugawi, OziExplorer, Pathaway, etc. You can skip the GPSr if you buy a PDA with a built-in GPS, such as the Garmin 3200 or 3600 Palm PDAs. The only downside with these is that they are generally not as robust as a hand-held GPSr, and the stability of the OS, GPSr and mapping software combination isn't going to be as reliable as a hand-held GPS. Still, this would be a good solution if you don't want to go the route of using a laptop computer to run your mapping software.
GeocachingI've seen some GPSr's with special Geocaching (see www.geocaching.com for more info) features, and the latest . Geocaching features are useful but they don't help you find the cache any faster than a regular GPS. Basically, for Geocaching you would want a GPSr that can store waypoints, display a bird's eye view of my position in relation to the waypoint, and display position and bearing information. And that describes almost all GPSr's on the market, including most entry level units. I would only recommend spending extra for a unit with Geocaching features if it can store full cache data (such as difficulty rating, description, logs, hints, etc.) for each cache waypoint. Having all that data on a single device would make caching a lot easier.
Here's an example of the geocaching features of the Garmin 76C:
Built-in Altimeters and CompassesIf you're a hiker, a GPS with altimeter might be a good thing to have. But as for a built-in electronic compass, I'd stick with a reliable liquid-damped, magnetic needle compass. They don't require any calibration and, with a paper map, will serve as a back-up navigation system should your GPS ever fail. You should NEVER rely solely on a GPSr for navigation in the back country.
External AntennasFor fourwheelers, this hasn't changed much. When driving in heavily treed areas or along mountain trails, signal reception can be problematic so I still advise you to buy a GPSr that will accept an external antenna. Also remember that steel (like in vehicle roofs) and some tinted glass (usually the kind that is bronze coloured) will interfere with GPS signal reception, so even if you're driving on the highway, an external antenna may still be required. Yes, you can buy a re-radiating antenna so you don't need to buy a GPSr with an remote antenna socket, but for the extra cost of such an antenna, I think it's a better idea to put that cash difference into a more expensive GPSr with the antenna socket. A good remote antenna such as one by Gilsson only costs around USD$20!! The best place I've found on the Internet to buy GPS antennas (and other accessories such as cases, power/data cables, and data cards) is at GPSGeek.com. With their prices and product performance, there's really no excuse not to get an external antenna for your 4x4.
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