People new to GPS will sometimes ask some variation of the question "What GPS Receiver Should I Purchase?".
We provid you both specific technical information, and some general advice that applies to any purchase of a GPS receiver.
Depending on how you plan to use your GPS receiver, some features may be more or less important to you. Some of the things to consider when deciding which GPS receiver to purchase:
Cost. While this is an obvious factor, you should be aware that some GPS manufacturers, such as Garmin, have policies that require dealers to advertise in a way that doesn't necessarily reflect the lowest available price. You should always check with retailers for the actual price. Some dealers may have remanufactured or overhauled GPS receivers, with a full warranty, for a better price than a new receiver.
Data/power connection. At some point, you will probably want to be able to transfer data, such as waypoints, between your GPS and a PC/laptop/PDA. Some low-end GPS receivers do not have the ability to transfer data, so they may not be the best choice. Some GPS receivers can be powered from an external source, such as 12 volts in an automobile or boat, which may be an issue, rather than relying on batteries in the GPS receiver.
Apples vs Oranges. Make sure when comparing different GPS receivers, whether from the same or different manufacturers, that you are doing a fair comparison. GPS specifications and features are not always presented in the same manner, even within models from the same manufacturer. One factor that is sometime overlooked is whether or not the GPS receiver comes with a data cable, used for transferring data to/from the GPS, and for doing firmware upgrades. If a cable is not included, you will have to include the cost of making/buying one when comparing prices. A GPS receiver that does include a data cable may not have the option to purchase it with a combination data/power cable, so the cost of that additional cable would have to be taken into consideration, if you want such a cable.
Accuracy. If the accuracy of the position reported by your GPS receiver is an important consideration for your intended use of your GPS receiver, then you should take some time to understand how the Global Positioning System works, and the limitations of GPS receivers. Consumer-grade GPS receivers are used in a wide variety of situations, but are not suitable for things like determining property boundaries, or if you need "sub-meter accuracy". You should also be aware that GPS receivers, when reporting a position, despite what you may see on your GPS display, can not tell you the accuracy of the reported position. GPS receivers will instead report the Estimated Position Error(EPE), which is an estimate of the likelyhood that, some percentage of the time, the actual location of the reported position is within some distance of your current location.
Maps. If you are interested in a GPS receiver that can display maps, stop looking at specific GPS receiver models. The first thing you should do is to instead look at the maps available from the GPS manufacturers. Once you have decided which map product is the one you want, then you will have to look at only the mapping GPS receivers from that GPS manufacturer, because each manufacturer uses their own map format. You should then decide on how much map memory you will need in your GPS receiver. That will depend on the mapping product, what maps you will need, whether on trips you will have a laptop so you can upload more maps as needed, whether the GPS receiver supports storing maps on removable media, etc. Mapping GPS receivers generally only support the use of maps in the manufacturer's own map format, so you will not be able to use "map images" such as JPEG images on your mapping GPS receiver. Some people elect to purchase a non-mapping GPS receiver and spend the money saved on purchasing mapping software for their PC, which will work with map images, allow for pre-trip planning and post-trip analysis, and allow for printing custom maps for use on your trips.
Features. Different brands and models of GPS receivers have different features, and which features are important largely depends on how you plan to use your GPS receiver. Once you have done some initial research into your GPS receiver purchase, if you are unsure about something, you can try asking your question in one of the GPS-related newsgroups. For example, if you have never used a GPS receiver, and aren't sure if a particular feature is important for hiking, then asking the question in the GPS-related newsgroups will likely get you the opinion of fellow hikers who use a GPS receiver.
How will you use it? Does the GPS receiver display all the information you want, either on a single screen, or on multiple screens with easy navigation between screens? Does it matter which hand you use to operate the GPS receiver? Are the buttons/controls easy for you to use? Is the GPS receiver designed to be operated horizontally or vertically, and how does that relate to how you plan to carry(e.g. while hiking) or place(e.g. while driving) the GPS receiver? Is the GPS receiver's display readable given your eyesight, and viewing habits(e.g. in direct sunlight)?
Antenna. Due to the antenna design, and placement in the GPS receiver, some GPS receivers are designed to be operated horizontally, others vertically, which may be a factor in how you plan to carry the GPS receiver while hiking, or riding a bike, or while driving. GPS receivers that do not have a connector for an external antenna can be used with an external re-radiating antenna. An external antenna may be needed in difficult reception conditions, such as under tree canopy, or in a vehicle with a windshield that blocks GPS signals.
Automotive
Handheld
PDA
Laptop
Aviation
Marine
Handheld GPS units can vary somewhat in size. The smallest ones are about the size of small cell phones. The largest ones are the size of a typical television remote control.
They are self-contained, meaning there are normally no external attachments. There are some exceptions:
Some receivers can run on external power, such as from a car.
A few models have a jack for an optional external antenna.
Some units can be connected to a laptop or PDA for expanded uses.
 Automotive - These are larger than handhelds in order to accommodate a screen large enough to be seen while driving. They are powered by the car's electrical system and because of this, they can only be used in a vehicle. Automotive units usually have voice instructions to allow you to navigate without taking your eyes off the road. Prices start at about $500 US.
Many automobile manufacturers now offer built-in GPS receivers as an option. Because they are built-in, the big advantages are security and aesthetics. They are generally more expensive than add-on units and often have fewer options. Some people also report difficulty getting map updates.
 Basic handheld GPS receivers - These are going to be the least expensive choices for GPS - often less than $100 US. Basic receivers are as accurate as more expensive units, they just don't have as many features. The main feature they lack is mapping capability. Here is a list of what most basic receivers display/have:
- Location, usually in the format of your choice.
- Compass heading.
- Elevation above sea level, although elevation accuracy is not as good as position accuracy.
- Accurate time, usually in both 12 and 24 hour formats.
- Satellite location and signal strength.
- The ability to calculate distance traveled.
- The ability to record your path as a set of waypoints.
- The ability to navigate routes.
- The ability to retrace your steps.
Handheld mapping GPS receivers - These units display pre-loaded maps and/or maps uploaded from a PC. Map detail is reflected by the size and resolution of the screen. This means that mapping units are generally larger than basic units. Although mapping units are more expensive than basic units, the increase in cost is not all that much. The cost of adding map display capability to basic GPS receivers is low enough that many manufacturers are including it in less expensive models. Prices start at about $150 US.
 Maps that can be uploaded from your PC are on purchased CD-ROMs. On your PC you can view the maps, mark and name waypoints, and create routes. This information then can be uploaded to the GPS receiver. Keep in mind that the handheld unit can hold only the amount of data dictated by the size of its memory. Many mapping receivers accept memory storage cards - usually Secure Digital (SD) or Compact Flash (CF). This means that if you find you need more storage space a larger memory card can be purchased.
It is highly recommended that you have a paper map and a magnetic compass along when using a GPS receiver. The first reason is safety; if you're out in the middle of nowhere and in the unlikely event that your GPS bites the dust, you will need a backup means of navigation. Besides, paper maps and magnetic compasses don't need batteries. The second reason is more of convenience than anything else; with a paper map (even along with a mapping GPS), you can more easily get the "big picture" of where you are and where you want to go simply because the paper map covers a larger area at one glance than a GPS screen can.
 GPS for a PDA - Advantages of using a PDA as a GPS include a large screen for easier viewing (and more detail) of maps and voice prompts for driving directions. There are several different ways to integrate GPS with a PDA.
Sleeve - A sleeve is an attachment which wraps around a PDA that adds many different functions to your PDA. It does this by providing a CF (see Compact Flash below) or PCMCIA slot. A sleeve can add memory, battery power, a camera, a phone, and, of course, GPS ability. An advantage of the sleeve is the fact that it gives you a CF slot that you can use for other things besides the GPS. And, the newer GPS sleeves perform better than the older ones. The performance of a sleeve GPS is about the same as a CF GPS. Most sleeves come with a windshield mount which is a bonus if you plan for in-car use.
Compact Flash - Compact Flash (CF) is one of the standards for PDA attachments that attach via a slot on the PDA or its sleeve. A CF GPS card is a relatively inexpensive choice. There are two minor disadvantages. The CF GPS of course requires power, so it will drain your PDA's batteries quicker. Also, the CF GPS sticks out of the top of the PDA, making it a little clumsy.
Bluetooth - Bluetooth technology allows wireless connections between devices. For instance, you could be holding/wearing a Bluetooth-enabled PDA that is communicating to a GPS device in your backpack. Bluetooth is also good for in-car use because the GPS receiver can be placed forward on the dash for a better "view" of the sky. In exchange for the flexibility, you're going to pay more for a Bluetooth system for your GPS needs. The extra expense is incurred because in addition to the GPS function, it also incorporates the relatively new Bluetooth technology.
Cabled to a hand-held GPS receiver - Most hand-held GPS receivers will accept an optional cable with which you can connect your PDA. If you need an all-purpose GPS unit, this may be the way to consider. With a hand-held GPS receiver, it can be used either for walking/hiking or in the car. It is also an inexpensive choice. The PDA with its display larger than the hand-held GPS is good for viewing maps. And if you choose, you can always use the hand-held by itself.
Cabled to a car-powered GPS receiver - For use with your PDA, a mouse-type car-powered GPS receiver is available. It is called a "mouse" (it looks like a computer mouse) to differentiate it from the more expensive stand-alone car GPS receivers.
If you're going to use your GPS in the car, then this option is great for a several reasons. First, the mouse is powered from the car, which doesn't drain your PDA's batteries. Second, mouse GPS receivers usually come with a Y-cable that will power the PDA too. Also (and this is a big plus), these mouse-type units are generally the least expensive choice.
GPS for a laptop - The same as GPS for PDA above with the exception the sleeve (there is no such thing as a sleeve for a laptop). Keep in mind if you want to use a CF GPS with a laptop it will be sticking out of the side of the laptop, as in the illustration at the right. Also, if you're using a CF GPS with a laptop on the seat of an automobile, the reception will not be as good as a type of unit that can be placed on the dash where it has a better "view" of the sky.
The Global Positioning System, GPS receivers, and how to use them can be a complex topic, even for recreational users. Two ways to approach a purchase decision:
- Just go out and buy something! This approach will work if money doesn't matter to you, or you are willing to buy another GPS receiver if you discover you didn't buy the one you really needed. One realistic approach is to buy a basic, non-mapping GPS receiver and then make use of it to become familiar with the operation of GPS receivers. Later on, if you decide you need a different receiver, you can possibly sell the basic receiver, keep it as a backup, or give it to a relative or friend.
- Do some reasearch first to make an informed decision about which type of GPS receiver is best for your needs. The downside to this is that it will take some time to do the research, and even then you may not discover what you really want until you get out and use your GPS receiver. Don't rely on what you are told in the store by the salesperson. See if you can borrow a friend's GPS receiver, and go to an area such as a park and figure out how to use the GPS to navigate.
Driving - For GPS use in an automobile, there are several choices: 1) Basic or mapping handheld receiver; 2) Dedicated automotive receiver; 3) GPS with a PDA; 4) Laptop GPS;
1 ) Basic or mapping handheld receiver - Handheld units can be used in a car but keep in mind that a) The screen can be hard to see due to its small size; b) Some units will need to be placed forward on the dashboard where they can get a better "view" of the sky. A basic (non-mapping) unit can tell you where you are as long as you have a paper map with you to interpret that data.
Since the nature of driving usually involves roads, a mapping unit is the more useful choice. Using a handheld in a car will require changing batteries unless you purchase an auto power adaptor, which is available for many models.
2) Dedicated automotive receiver
3) GPS with a PDA - First, let's consider that the setup will need to have relatively clear access to the sky for satellite reception. Some GPS receivers have the antenna built in and some have capability for an optional external antenna. An antenna on the seat of your car may or may not work. The console is the next best place - reception may be questionable. An air vent mount is better and a windshield mount or the antenna placed all the way forward on the dashboard is better yet. The most reliable place is for an external antenna to be attached to the roof of your car.
The antenna may be physically attached to the PDA, such as a sleeve or CF. Or it may be separate, as in the case of a PDA cabled to a handheld GPS receiver, a PDA with a mouse-type receiver, or a Bluetooth unit.
A PDA can simply be placed on the passenger seat. Getting a mount is better because it is safer and more convenient. Mounts are made for the console, air vents, dash, and windshield, although the windshield mount can block your view of the road.
Hunting/Fishing For hunting or fishing you will be pleased to know that many handheld models include best hunting and fishing times for a given location and date. For fishing, you can also consider a chart plotter/GPS or a GPS sounder. The chart plotter/GPS and GPS sounders usually have a lot of features and start at about $400 US.
Hiking/Backpacking - For hiking or backpacking there are three choices: 1) basic handheld receiver; 2) mapping handheld receiver and; 3) (pushing the limits of practicality) GPS with a PDA. In addition to your GPS, paper map, and magnetic compass, plan on taking extra batteries. Handheld receivers last anywhere from 10 to 22 hours depending on the model and how much you use the screen backlighting. Expect much shorter battery times with PDAs.
1) Basic handheld receiver - Weight and size are probably considerations and a basic unit will usually be adequate. Since a basic receiver has no mapping ability, it will display your location in the format you choose, most likely latitude/longitude. Providing your paper maps have your chosen position format marked on them, your GPS will allow you to find your location on the map. If your maps don't have the position format grids marked already, this is something you'll want to do yourself.
2) Mapping handheld receiver - Often, mapping units are larger (and of course heavier) and/or have shorter battery lives than basic units. Shorter battery life translates into more extra batteries needed (more bulk and weight). If you can afford the possible additional weight and price, you will have the benefit of having the maps displayed on your GPS. This benefit comes in the form of convenience because regardless of what type of GPS receiver you have, you'll still have a paper map anyway (right?). And there are two more pluses: a) Mapping units usually have more features (than basic units) such as a barometric altimeter, an electronic compass, games, and a calendar; b) You can plan your route ahead of time on your PC and upload it to your GPS.
 3) GPS with a PDA - The advantage to this setup is that you can display larger maps on your PDA than a GPS. The obvious drawback is the extra bulk and weight. But if you're really roughing it and going to have a your PDA along with you anyway, this may be a logical choice.
4) Laptop GPS - Since a CF GPS is attached to a laptop, the antenna, which is integral to the CF/GPS, won't be in a very good location. Therefore, for reliable car use, a laptop will require a CF with an external antenna, a Bluetooth GPS receiver, a mouthe-type GPS receiver, or be connected via a cable to a handheld GPS unit so the receiver can be placed in a position for good reception. Of course a laptop is large, but the main advantage is a very large screen for maps. If you have a need for a laptop in your car anyway, this choice may be logical. A mouse-type GPS receiver to go with your laptop is also rather inexpensive.
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