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All kinds of GPS devices. How do I pick one?Mar 12 '03 (Updated Mar 09 '04) Write an essay on this topic.
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The Bottom Line All kinds of gps devices, pocket pc/palm pc offer other functions besides gps, mapping gps units are only as good as the maps.
I am writing this in an effort to talk about the several different types of gps receivers and help others to make a better decision about which unit to buy for themselves. What is a GPS? GPS stands for Global Positioning System. The united states government has a fairly large number of satellites in orbit around the earth (not geosynchronously) and each of these satellites emits a signal. A GPS unit listens for these signals and by locating at least four satellites, a GPS unit uses math (trigonometry?) to "triangulate" your position (the fourth satellite is needed for error correction). If you've been watching the news lately you've probably heard many references to military hardware (tanks, bombs, unmanned spy planes) that use gps signals for navigation and targeting of weapons. Over a year ago the US government allowed commercial use of the signals from these satellites, it is no longer restricted to military use only. There are however two different signals being transmitted, one for civilian use and a much more accurate signal that is only available to the military. There are currently plans to upgrade the system to have 4 available channels and a higher signal strength and that project is planned to begin sometime in 2004 if the funding is avilable. If these new satellites become a reality there are plans for a higher accuracy channel available for civil use. Types of GPS: GPS units come in several varieties. Handheld units, which may or may not, have actual mapping capabilities beyond just tracking your route, routing you back to your point of origin, and telling you your coordinates. Vehicle mounted units that are designed to be installed in a car, boat, plane, etc., run on 12 Volt power provided by the vehicle and may not be portable at all. Internal or external units designed to be used with a palm pc, pocket pc, laptop or tablet computer and may be self powered or run off the computer's internal batteries. What makes one gps receiver better than another? I've used a couple of different hand held and pc/pocket pc based gps units. The single most annoying part of using a GPS for the first time is the "cold start" when the unit has to "find" the satellites above you for a few minutes before it can triangulate your position. While it's finding the satellites it is downloading ephemeris data and once every couple of months it also must download new almanac data that tells where the satellites are located. A good gps should locate the 3 plus satellites it needs in a minute or two from a cold start, a less well designed unit can take much longer (one I tried took ten minutes!). Even after the first cold start lag, if you go inside a tunnel/building/rock outcropping your gps will need to "reacquire" the satellites when you come out from under the obstruction of the sky. A reacquisition should take much less time than the original cold start. A good gps will have some kind of internal memory that helps it remember the satellites and thus lets it find them faster on the reacquire. Every few months a new almanac of satellite positions must be downloaded and under excellent conditions this can take ten minutes so occasionally you're going to have an extra long wait on a cold start. Ephemeris data is generally only good for a couple of hours but that generally takes only about 30 seconds to download. Another feature that should be considered in a portable gps, is battery life/power consumption. Most handheld gps units use either AA batteries (alkaline or rechargeable) or some kind of built in rechargeable battery package. Computer based units can either run off the laptop/palm device internal batteries or be self powered. I haven't used enough of these units to really tell you what "good" battery life is, but it's been my experience that manufacturer's claims are often way out of line for what you get in "real life" conditions. So if they claim 24 hours on a charge or set of batteries, you'd better believe it's probably much less than that by at least a third. In the case of a laptop or pocket device powered gps, the issue of battery usage can be a big deal. While a laptop can probably handle it pretty well, battery life in pocket pc devices already tends to be poor and the addition of a gps could really drop your battery life into the unacceptable range. High capacity batteries are recommended if you plan to use a compact flash or sdio gps unit on a pda. The third and fourth most important features to look for in a gps involves only those units that have mapping capabilities. The ability to update your maps is very important. Units with mapping capabilities will provide one of two ways to do this, either flash (non-volatile) memory cards, or some type of connection to a PC computer. Last but not least the size and quality of the screen is very important. A gps with a color screen will cost more than a gps with a black and white or grayscale screen but it may be much easier to read than a grayscale unit. GPS Units with mapping capabilities: What is a mapping GPS? A mapping GPS has actual city or county or even ocean maps installed and can actually point to your position on a map displayed on the unit's screen and continually update your position if you are moving. In addition to pointing to where you are, information such as topographical (elevation) maps may also be provided. A mapping gps also may or may not have the ability to actively guide you with voice prompts to your destination and save "favorites" for later return to the same position. A mapping gps package can usually be given an address where you want to go and the unit will draw your route, reroute if you get off course, and depending upon the software, actually give you "turn by turn" (also called dynamic routing) voice directions to get to your destination. For someone traveling in an unfamiliar city, a mapping gps setup could be a real time saver. Many rental car companies are beginning to offer mapping gps units in their rental cars, usually for a hefty daily fee. Any mapping GPS you purchase is only ever as good as the maps it has access to. Cities are constantly adding or changing streets, installing highways and building new subdivisions so maps can change fairly frequently. A good mapping gps unit will have some method of installing new maps on it. I've seen handheld units that used a flash memory card (such as compact flash, secure digital, mmc, XD, or even proprietary flash memory cards), serial connection to a pc rs232 port, bluetooth connection (wireless), or usb connection to a pc to allow you to update your maps as necessary. The single part of a mapping gps that makes them expensive has to do with the amount of memory the unit has to work with when loading maps etc. Obviously it would take a fairly considerable amount of memory to have city maps for all fifty states available to the unit at all times, which is probably one reason why many vehicle mounted gps units are still in the 900 plus dollar range. I feel that of the mapping gps units, those that are based on a palm device, a pocket pc device or a laptop/tablet computer are the easiest to update and use because the mapping functions run on the computer and not on the gps unit itself. Pc based maps also also tend to offer the ability to zoom in on the map and list all the street names and major points of interest around you. You'll also probably find that units that need some kind of "proprietary" flash memory card are going to cost a lot more for map updates than those that offer map updates that can be downloaded to a pc and updated in the gps memory via a computer connection or some variety of standard memory card such as compact flash or Secure Digital. PC based GPS units: As I've got the most experience with pc based gps units, I'll be focusing most on the benefits these units provide. When picking a pc or pocket pc/palm based gps unit it's best to look for one that complies with industry standards and is not "proprietary." A pocket pc, palm device, or a laptop and a gps is a major investment. When you upgrade in a year or two you don't want your gps purchase to be incompatible with your new hardware! When you have a GPS unit that complies with the standards, any piece of mapping software you could want should work properly with it. Software is a "preference" thing, my favorite package may not be yours and there are at least 5 to 10 competing mapping packages that can use a gps are available at this time. PC based GPS units come in two varieties, internal and external. An internal computer based GPS plugs into the pocket pc, palm device, or laptop/tablet by way of a compact flash slot or pcmcia slot (perhaps soon a secure digital slot unit will become available but I have not seen any currently for sale). An internal GPS is powered off the machine's internal power supply. An internal GPS will usually have a plug on the side for the installation of an external antenna for better reception. An external computer based gps is connected to the pc in one of several ways and usually has its own power supply. Several connection methods I've seen include the following: Serial: Proprietary cable that connects to the serial port, or in the case of a palm pc or pocket pc device to the proprietary "sync" connector usually located on the bottom of the pocket device (this is also a serial connection). Units that connect in this way may or may not have cables that can be changed according to the device you are using it with, I would avoid units that will only work with one device and don't offer interchangeable cables. USB: Most palm or pocket pc devices that I've seen do not have a true usb port on them so this type of connection would usually be limited to a laptop or tablet pc device. USB connections provide power and data connections so a unit connected via usb could be self powered or powered from the laptop's internal batteries (perhaps even both options would be available). Bluetooth wireless: Bluetooth is currently one of the more widely available varieties of wireless networking, any device equipped with bluetooth can in theory communicate with any other device also equipped with bluetooth. A Bluetooth gps would only need to be turned on to have it "talk" to your bluetooth enabled palm, pocket pc or laptop/tablet computer. The big advantage here is no wires, you could mount the gps on the windshield where it can see the sky and have the laptop or pocket device sitting on the seat with no problems. Miscellaneous: Compaq produces a popular line of pocket pc devices that can use "sleeves" to add additional functionality. There is at least one gps product that is provided as a sleeve for a compaq pocket pc. What kind of computer or pocket device should I get to run my GPS and mapping application? Any laptop made in the last ten years should be able to run a GPS application just fine. Most laptops have pcmcia slots that can run either a pcmcia gps unit, or with an adapter a Compact flash gps unit. if you don't want internal, several of the external units and connection types are available depending on the laptop. A color screen is a good idea as well (I don't think anyone is making grayscale laptop screens anymore but I could be wrong on that). Pocket devices: The big advantage to a pocket device is the small size of the unit and the fact that it can do lots of other things besides just run your gps package. Most pocket pc devices these days are at least 64 RAM/32 ROM which I consider the minimum for running a GPS and mapping application; however the toshiba e800 series and the ipaq 5555 come with 128 meg of ram which I'm sure any mapping setup would love the extra memory. There are two types of pocket device and the gps device will not necessary work with both unless it's an external unit. The two competing types are pocket PC and Palm OS. I won't get into the advantages and disadvantages of each competing type of pocket device here but basically the big difference may be battery life, the software available for it, and the type of storage slot the unit offers for map storage. Palm devices are known for long battery life while pocket pc is the opposite. Software seems to be more available for the pocket pc because it is a microsoft product and pocket pc devices often offer more storage options than palm. If you use your gps primarily in the car where you can plug your device into the cigarette lighter, then you probably don't care about battery life that much. If, on the other hand you want to take it hiking then battery life is a big deal. If you go with a pocket pc device look at a device such as the Toshiba e740, the newer e800 series, or the Dell Axim X5 Advanced. All of these units offer a compact flash slot and a secure digital slot on the unit (where many newer pocket pc devices have an SD slot only) so you could conceivably use a compact flash gps, and have your maps stored on a secure digital card. The toshiba's also offer WiFi wireless networking. The e740, and the x5 advanced offers 64RAM/64ROM which is more than should be needed to run your mapping software, the toshiba e800 has 128 meg ram and a standard amount of rom and some flash memory storage that won't lose data if the power goes off completely. All three of these machines offer optional high capacity rechargeable batteries that will extend your battery life into the useable range (something above 12 hours I've read). Unfortunately I don't know very much about palm OS based devices but from all I've read the memory requirements are pretty much equal to what is needed on a pocket pc. Many maps for a large area can consume as much as 28K when the application is running and then there still must be room for the application itself to run. I've seen many complaints with Palm devices that only have 16K ram that are trying to run gps applications; they just don't work when the maps are too large. One last note here is that some handheld GPS units offer one of the external connections to a pocket device or laptop/tablet pc and can be used either way, as a standalone handheld unit or as a external GPS in conjunction with a computer based mapping software. What I ended up with: I got a Maestro pocket pc (same as toshibe e570, 32RAM/32ROM, CF and SD slot, nice color screen) for Christmas. The GPS package was an afterthought that I started looking at when I decided to start planning a vacation. After much research, reading reviews, and looking for the best price I ended up with the Holux GM270 Compact Flash GPS unit. This unit is based on a newer low power consumption chipset and because it is compact flash and works under the pocket PC operating system, it should be compatible with any newer hardware I should buy in the next few years. It also meets industry standards and should work with any mapping software I buy. This unit is also unusual because in addition to the ability to work on my pocket pc, drivers are available to use it, via a pcmcia adapter, in a laptop/tablet pc. The unit came from semsens.com and also included a subscription to Mapopolis Platinum Plus software and an external antenna and cost about $214.00. The software is ok but since I wanted dynamic routing functions I contacted the company to be upgraded to their navigator maps that provide the dynamic turn by turn voice prompted directions (an additional $50.00 but worth it). Semsons is currently offering this gps with the mapopolis navigator mapping for about $250.00 on sale. Everyday use: When using any gps in a vehicle you need one of two things, either an external antenna, or some method of mounting your pocket device on the dashboard or to the windshield so that the gps can see the sky. I've used both the external antenna and I bought a RAM suction cup mount for my windshield and used it without the external antenna. It works great, the Holux from a cold boot finds the satellites in under two minutes and reacquires in under a minute, I like this unit a lot. Software: Like I said earlier there are several competing mapping packages that work with a gps and run on a pocket device or laptop; which one you like has a lot to do with personal preference. My best suggestion is to read all the reviews you can find or post in newsgroups that cover this kind of hardware and software, you can also sometimes download a limited trial version of the package you are considering with sample maps. One big thing to remember with downloadable maps or updates bought on cdrom involves the age of the maps. Products like mapopolis are subscription based, the company buys the rights to a set of maps produced on a certain date and you can download the maps from that period as much as you want. You will not get new maps if any come out during your subscription, you won't get those till you pay again next year (sounds like a nice little racket there doesn't it). This has to do with the way maps are sold by the few companies that actually produce them. The company makes the maps and sells them to companies like mapopolis but mapopolis has to pay again when the new ones come out; just like you do. I've used my gps and mapopolis navigator in the tampa bay area of Florida, it's fairly good but often really small cities are not listed and some newer roads (2 years seems an awfully long lag if you ask me) are often not listed as well. I also think the search function could use a little work as it's sometimes hard to find streets without trying a few variations of the name. In fairness I haven't seen any packages that don't have a few complaints of this nature. update: Bought a new axim x5 advanced with 64/48 (16 meg non volatile flash memory. This machine runs my package better because of the faster 400 mhz processor. A 64/32 pda is currently the recommended machine for a mapping gps package. There are a couple of newer machines with more memory but the cpus are still at the 400 mhz mark. PDA sales are way down, we may be keeping the same technology for a long while now. Several of the newer machines are eliminating the Compact Flash slot, Secure Digital gps units are slowly becoming available but they are very expensive, personally I wouldn't buy a pda that didn't have a CF slot on it or an option to add it like the compaq ipag does. update: I've read recently that the US government has plans to update the 20+ year old gps satellite system. The new satellites are currently predicted to start launching somewhere around 2010. The new system will offer two new channels available for civilian use, one of which will offer accuracy approaching what is currently only available to the military. It sounds like the current frequency will still be maintained, there will only be two new additional frequencies made available for civilian use (thus your current hardware should not be made obsolete). Europe is apparently planning to launch a gps satellite system of its own and there is some fear that it could interfere with the US system due to overlapping frequency usage; this one is a current bone of political contention. GPS is very reliable but is not always 100% so, the FAA lists NOTAM advisories on their web page when the gps system is experiencing interruptions. You need your three letter local airport code to find out if there are any interruptions scheduled for your area (if you don't know your airport code cheaptickets.com or travelocity.com offers a lookup function). Recently in Florida we had a rather severe outage that covered most of the state, of course this happened while I was out on the road and suddenly had no gps service; lucky I still keep maps in the car!  |
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