Overview Types of GPS Receivers

There are different types of GPS receivers. Before deciding which receiver to buy, you might consider a quick read of the following. This could eventually change your decision.

Type 1: Not-self-contained receivers (without screen), also known as RS232 receivers or also GPS mice. This type needs a computer (often a Pocket-PC or Palm PDA) and according program in order to visualize the actual position of the GPS receiver. The link between the GPS and the computer can be wireless (Bluetooth), by means of a cable or via a card-slot or sleeve. This type is often used for car-navigation systems with moving map on the computer screen and for golf GPS systems. See also our Car GPS page.

Type 2: Self-contained receivers (with screen). Here the computer is integrated in the GPS receiver. We have to distinguish between non-mapping devices (often handheld) and mapping devices which can be handheld or mounted in boat, car or plane (often with external antenna). This type sometimes has extra features as a barometer/altimeter, an electronic compass or even a radio transmitter/receiver.

Peter Roosen wrote a very nice interactive tool to help us choose a GPS receiver. Unfortunately it is in German, so we made a brief recapitulation in English. The program, NAVIG2, and the translation can be found here.

If your primary use will be in boating or aviation, you should look for a receiver for those particular fields, as they offer you some extra features and readings that will be missing on general purpose models. On the other hand will a good handheld marine GPS receiver serve you perfectly on land.

Type 3: The more sophisticated receivers for professional use in agriculture, mapping and GIS, military, oil and gas, public safety, survey etc. The principle of these receivers is the same as the above, but they often use extra receivers and special antennas for higher accuracy and can often store an enormous amount of in the field collected data, which can be treated later in the office.

Type 4: Dedicated single-purpose GPS systems as there are the car GPS systems with a build-in GPS receiver, using maps from the device manufacturer. Very useful for this purpose, especially because you can take the system from one vehicle to another without hassle. So you can even use it in a rented car or Jeep, during your holidays, contrary to the fixed in-vehicle GPS systems. You can only use maps of the device manufacturer and you can not upload your own maps. See our Car GPS page.

Here we also have to mention the stand-alone golf GPS systems, which show you where you are in relation to various targets on the golf-course of your choice. Most models in this category will not perform good (at all) as a classic GPS receiver. See also our Golf GPS page.

Type 5: Very special applications, using GPS, as there are vehicle tracking systems (See our GPS Car Tracking page) and child-locator devices (See our GPS Locators page). Both use a GPS-chip to measure their location and some form of wireless phone system to communicate this information over great distances, eventually via Internet.

Type 6: Phones with incorporated GPS receiver. They could already be used for in-car navigation with street maps coming in through the air. End May 2005 Sylvan Ascent Inc. launched TopoPhone, which provides outdoor recreation enthusiasts with a better GPS solution by turning a cell phone with built-in GPS into a complete Topographic mapping system. TopoPhone is superior to traditional GPS units, because it uses the phone to download maps automatically, and allows you to see where your friends and family are located. See also our GPS phones page.

Mapping or non-mapping GPS receiver?
With a comparable mapping GPS you can do everything that you can do with the non-mapping one and more (example the Garmin GPSMAP 76 and the GPS 76). But neither into the non-mapping, nor into the mapping version can you load your own maps. Only maps of the GPS manufacturer can be loaded into the mapping GPS and if you want to use it outside of the US or Europe, you will probably not find suitable maps.

And if you are a walker or a hiker who uses small-scale topographic maps, you can probably forget it all together to find any usable map. As a mapping GPS is about 60% more expensive than the non-mapping version, you should only buy the mapping version if the manufacturer has at least one very good map (or marine chart) for your use or could sell it in the near future.

Even a non-mapping GPS receiver has a map page. The word is correct, but if you love beautiful paper maps, be prepared for a disappointment. It will only show some points (waypoints) and some lines (routes and/or tracks). For most navigation tasks however, you don’t need more.

And what if you absolutely want or need to use your own (digital) maps with your GPS?
Today’s PDA’s can store 1GB or more of data on removable memory-cards and are powerful enough to run sophisticated software that can move your maps and even zoom in and out automatically. So your maps and software are stored in your PDA and a separate GPS receiver, linked to the PDA, delivers the GPS data.

The most flexible GPS configuration
Almost every GPS receiver can communicate with a PDA (Pocket-PC or Palm). A good non-mapping GPS receiver will serve you much more than a car navigation system could ever achieve. As stand-alone classic GPS receiver it will be your guiding assistant wherever you are on land, at sea or in the air. Linked to a PDA with commercial navigation software and a route-planner, it is a complete door-to-door car navigation system.

Would you like to use your own (digitized) topographic maps with your GPS? In this configuration you can. All you need is PC software (See our GPS Software page) that allows you to geo-reference imported or scanned (topo)maps and a small moving-map software for your PocketPC. If you already have a PocketPC, running PC2000 or higher, this is definitely the way to go.

Choosing the Right Type of GPS
In order to be in a position to choose from the various GPS solutions that are present in the consumer marketplace, it is necessary to have a reasonable understanding of what they can offer, as well as what the user is expecting from the solution.

There are several components that need to be looked at. There is the GPS receiver (or antenna) itself, which plays an important part. Then there is the portion of the system which uses the received information to estimate where the device is located on an internal map.

Then there are the various capabilities for route planning and recording, which vary from unit to unit. Finally, the display portion of each solution type can vary considerably, from limited location information to full color three dimensional maps of the immediate surroundings and advised route.

How it Works
All GPS solutions are based on the same premise, and it is a good idea to at least be aware of the underlying technology so that an informed decision can be made as to which application of the GPS technology is appropriate for the user in question.

GPS receivers use signals from satellites which orbit the Earth at known positions. Each satellite has a unique identification code and sends a signal which the GPS receiver can use to calculate the distance from the device to that satellite.

Much like regular orienteering triangulation, this allows the software to estimate its own position from several (at least 3, preferably 4 or more) signals, by finding the point in space at which the spheres representing the distance from each satellite intersect.

From this location information, the software can then pinpoint the devices location on a map and use the information for a variety of operations, from simply displaying the location, to adjusting a proposed route based on the actual position of the device compared to the desired position.

Applications
There are three broad classes of application - road, hiking and maritime - and each is further subdivided into other types which offer different features depending on the exact use to which they will be put and the environment that they will be operating in.

One important thing to remember is that this technology does not allow the transmission of actual mapping data via the satellites. It is purely concerned with the location of the device.

The first application we shall look at is the in-car (or in-vehicle) GPS. These units need to be reasonably accurate, reliable, and contain details of all the roads, and important addresses (gas stations, railroads etc.) and points of interest for the region in which the device will be operating.

These devices may be part of the in-vehicle entertainment system, which ties them to a single vehicle. Or installed under the dashboard. Obviously the drawback is that they are not able to be removed from the vehicle.

Portable devices suitable for in-vehicle use exist, and offer a great alternative to those which are integrated within a particular vehicle. However, they will not be able to override the in-vehicle entertainment device (CD player, etc.) and so the voice commands might be drowned out by the music.

Then there are portable devices which are designed for general use, which have a limited road database, and reasonable terrain information. They are small enough to be carried in the palm of your hand.

However, a recent trend has seen PDA manufacturers attaching a GPS antenna, and providing sophisticated software and maps which use the power of the PDA to give an excellent solution. They might not be rugged, but they do provide a very good base for both in-vehicle and general navigation.

Rather than having a direct connection, many PDA - based GPS solutions use Bluetooth as a means to communicate with the GPS receiver. This makes them more easily installed in, and transported from, vehicles.

Finally, maritime units need very specific features, not least being that they should be waterproof, and containing additional information that can be plotted on nautical charts. Their maps are also very specific, giving undersea elevations as well as navigable channel information.

This includes devices such as fishfinders, which build other fishing related features into the basic GPS unit. A fishfinder is very useful for positioning, tracking and helping the fishing enthusiast to locate schools of fish at sea.

Associated technologies such as GPS Tracking have also evolved, where the user wears a watch which relays their position via radio to a central control center. This tracking information is then used in conjunction with an alert system to track anything from vehicles to people.

Updates & Mapping
When choosing a GPS, it is important to bear in mind that each type will be updated in a different way. For example, dedicated in-vehicle units tend to be updated via a CD, which has to be purchased from the road map data supplier.

Those which are attached to a PDA, as well as most handheld dedicated GPS devices, are usually updated via a PC. They also need maps, but said maps can usually be acquired at a much lower price than the dedicated branded ones needed for other systems.

Being able to update the device easily and at a reasonable cost is a very important part of the decision process; unlike other consumer devices that you purchase, the cost of ownership of a GPS unit is proportional to its usefulness.

The less you spend on maintaining it, the less useful it becomes since the road networks are always changing. This is perhaps less important for devices aimed at hiking and orienteering, but could be a factor in deciding whether a multi-function device is better than one dedicated to a specific use.

Specific software vendors have solutions for preparing maps which can be uploaded into the GPS unit. For example, many are based around the mapsource system which permits users to define their own maps, perhaps scanned from a real one, in order to get the most out of their GPS.

Accuracy & Portability
If accuracy is paramount, then it is also important to choose a unit that is equipped with a WAAS (Wide Area Augmentation System) capability assuming it is available in the region the unit is being used.

This is a satellite service which provides additional correction information to the GPS receiver which enables it in order to increase its accuracy.

WAAS equipped devices might be especially useful for road users and those involved in either door-to-door selling, or providing a service which requires them to be able to pinpoint their position right down to a few feet.

On the other hand, it is useless to purchase a WAAS capable system if the service is not available in the area in which the device is to be used.

If portability is a key part of the decision process, then it will usually be a trade-off against accuracy, whether that accuracy stems from poor GPS signal acquisition, or less powerful software coupled with a less detailed map.

The Choice
In the end, the choice is reasonably straightforward – buy the most expensive GPS that fits your needs; if price is a deciding factor, then buy the most expensive one you can afford which fits your needs.

Try to think about the following:

Portability
Features
Mapping and Updating
Environmental Features
Portability is affected by weight and size, as well as the antenna. This could have an effect on the features that the device offers – clearly if the screen is tiny, and the whole unit is about the size of a cell phone, then some advanced features will not be fitted.

The mapping and updating capabilities are also important. Should it be able to accept any old map from a PC, or is it enough that the unit is replaced after 5 years? Technology moves almost as fast as the roads are updated, so this could be an option.

Finally, are there any specific environmental options that are needed, such as waterproofing, rugged shock-proof design, or other features that make one device more attractive than another?

Answering these questions will help determine what type of GPS receiver that is right for you, and at the right price.