---------- ---------- PC Pro Realworld Computing: Paul Lynch - PDAs

GPS

I've been following the success of the various in car information systems with a lot of interest. The thought that I could be warned of traffic jams ahead, and never ever again have to spend two hours in a queue watching my radiator come to the boil, really appeals to me. The automated information signs on motorways showed that there are ways that this kind of system could fail. In a very big way indeed. Driving past a sign that says '30' on an empty motorway isn't exactly comforting, but you come to realise that it means that the system has finally caught up with the jam that was there two hours ago. The new signs for the M25 are a lot better, they suffer from the fact that the M25 always has traffic problems, so they might just as well put up fixed signs to that effect.

The TrafficMaster YQ (there is a plain TrafficMaster system as well, but it is audio warnings only) system seemed as if it might have a solution to that problem, if an expensive solution. You can mount it in your car, and detach the full unit (which is a similar size to a Newton) when you park the car. It can display a map of the area you are in, and relay information about traffic problems, with the promise of frequent updates. Better than that, you get a limited news and weather service. However, it only displays very coarse maps: it starts on the South East of England (for me), and can only zoom in as far as showing the NW sector of the M25. The frequency of update means that you can reliably get information about the daily commuter jams on the M25 and M4, but as I said before, they have become a fact of life. If you live in your car, it's a solution, but it lacks the ability to show a close up of local roads.

There are new systems coming that will show local route information, like the Philips Carin. But then you need to buy a big new BMW to readily get the system. They are also totally impractical if you happen to ride a motorcycle. A voice alert system (the cheaper TrafficMaster) can be connected up to a motorcycle intercom system, and handles traffic warnings, although less well, but it doesn't begin to address the whole issue of tracking routes or finding yourself when lost. Given the number of programs for PDAs to show map data, I was hoping that I might be able to put together a realistic substitute.

For years now I have kept a Psion Series 3a with Autoroute on an SSD, just to do quick checks of directions and route calculations for me. But Autoroute would never show the local villages around where I live, and it doesn't much help if you are lost. It can be just as handy to print out a route table from a desktop copy of Autoroute, and hope you don't get lost.

Windows CE has Pocket Streets, but that is effectively USA only, and it lacks the route calculation function. Mapper is a well established and respected shareware program for the Psion Series 3, and has just been released for the Series 5. It too lacks the ability to calculate routes. One of the first commercial software packages released for the Series was EnRoute, from Palmtop Software, who released the free Spectrum emulator for the Series 5 discussed in last months column. EnRoute will calculate routes just like Autoroute, and instantly endears itself to me by showing the local Buckinghamshire villages around here.

This type of software is well and good, but needs something more to make it really start to address the problems of moving around in a car. And if you aren't a car driver, but instead ride a motorcycle, you can't so easily stop to press buttons and find out where you might be, by looking in a combination of map books and mapping software. The biker problem is mostly down to weather protection. Any hardware has to be wrapped up securely against rain, be easily accessible on the top of the tank of your bike, and be able to survive when prodded by a safely wrapped up finger the size of a sausage, and with the sensitivity of the sort of condom favoured by Cassanova. This isn't too bad; with a car you are tempted to look things up while moving along, which really isn't a good idea, whereas with a bike the odds are good that you'll be bright enough to stop before attempting to operate a PDA.

The missing piece of the puzzle is a GPS (Global Positional System) unit. These are small devices, about the size of a typical PDA, and most will run on batteries and connect to a serial port. If you are considering one of these, there are a couple of things you should look for. Make sure that they can be battery operated; some require a 12V supply like you would get on a yacht, or in a car. The battery life is quite significant, because you will leave the GPS device on all the time you are using it, which could be several hours for a reasonable car journey; don't expect to make use of an idle timeout like on a PDA. It doesn't much matter if they have a display or not, but they must support NMEA 0183, either version 1.5, or preferably 2.0. The socket they use is a standard for GPS units, and you will need a cable to connect to a 9 pin PC serial port. GPS units often are advertised on the basis of how many satellites they can receive (which affects accuracy and speed of picking up a signal, which will matter to you), and also the number of waypoints and routes they can store. This latter point is only of interest if you intend to use the GPS unit on its own, or in areas where you don't have any mapping information on a PDA, like the Arabian Desert. The price range is likely to be from about 100 to 500, depending on the facilities; for PDA use, the cheapest that supports battery operation and NMEA is likely to be the best bet; the added features for the extra price are really only relevant for stand alone use.

The GPS device I have been using is a Garmin GPS II+. This is a relatively recent product, but at the upper end of the handheld price range (just under 300 from Maplins, who carry a good range of GPS products). It uses four AA cells to power itself for up to 24 hours, and supports NMEA 0183 2.0, so matches my requirements.



Garmin GPS II+ was used for all these tests
Garmin GPS II+ was used for all these tests

On its own the GPS II is very useful. It will show you your exact latitude and longitude, to an accuracy of about ten metres. It will also show altitude, but seems to be a lot less accurate in this dimension; standing still, I have seen it range between -200 feet and 420 feet for the same spot. It has an accurate time signal, and what seems to be a very accurate speed indicator. The speed display appears to lag by a couple of seconds, and is obviously subject to the +/-10m inaccuracy of the unit. While you are moving it displays a compass heading, but don't expect to stand still and swivel around and still see the direction change; it doesn't work like that.

You can mark various coordinates with labels called waypoints, and it will display a map showing your track and any waypoints in view. This is very interesting to watch in its own right.

One problem with GPS units in general is that they are very sensitive to obstructions, much more so than mobile phones. If you go indoors you should expect to lose the signal immediately. Even driving down a tree lined road will cause brief gaps in the signal. Some cars bodies, or even the rake of their windscreen, can obstruct the signal enough to make it annoying: this isn't a problem with a bike, or if you own a plastic car.

To connect a GPS unit to a PDA you will need the special GPS connector cable, a null modem converter, and the serial cable for your PDA. You may need adaptors to convert from 9 pin RS232 to 25 pin and back again, if you can't find a 9 pin null modem converter. Some PDAs may have custom cables already made up for GPS use, in which case get one, as they save a lot of bulk. You will also need some software on the PDA to test it. If you have any type of serial communications software, you can set it to 4800 bits per second and 8 data bits, and it will show you the NMEA data on a constant basis, so long as the connection is made. NMEA records are in ascii, start with a $ sign then a five character record code, and then are a sequence of comma separated numbers. You should at least get some records sent every two seconds or faster.

The GPS unit should be set to send NMEA format, and not to listen; several different combinations of sending and receiving formats are likely to be available.

There is specific GPS software available for most devices; I have seen products for Newton, Windows CE, and PalmPilot, as well as the Psion Series 3 and Series 5. Most of these products are geared to aircraft flight planning, apart from EnRoute and Mapper on Psion. There is a useful tester for PalmPilots, which will show the basic location date being sent from the device.



The PalmPilot GPS tester is useful for a preflight check of a GPS
The PalmPilot GPS tester is useful for a preflight check of a GPS

Remember that EnRoute will require the serial port for gathering GPS data, so disable the remote link from the System screen, and make sure that you aren't running Mapper with GPS activated or any other comms program at the same time as EnRoute.

Both EnRoute and Mapper display GPS data in a similar way; they centre the map display on the position relayed from your GPS, and that's about it. There's a lot more GPS information that I'd like to have easily available, including speed and heading; there are various programs available for the Psion Series 3 that will handle this, as well as other functions useful with GPS. Mapper makes a good try and shows a time remaining to reach your destination; because Mapper uses public domain data it is only accurate to within one mile, so you have to guess a bit as you get close to your destination.



Mapper shows direction when moving with a GPS
Mapper shows direction when moving with a GPS



and time to arrive when you have a route selected
and time to arrive when you have a route selected

Using the GPS/Psion combo in a car is mostly a matter of positioning it so that you can see the screen and still see the road clearly. Some velcro mounts on top of the dash mean that you make a permanent place for both units, but duct tape or Blutak work just as well for a quick tryout. One problem with the Psion Series 5 is that it naturally opens almost flat, so you have to devise something to hold it at the right angle to read on the dashboard. I was able to prop it up in front of the gear lever and resting on the radio, which was convenient for me to use.



setting the Psion Series 5 on the dash so that the screen is visible
setting the Psion Series 5 on the dash so that the screen is visible

The GPS will stay on while you are using it, which is good as it takes several minutes to acquire a proper fix after being turned on. The Psion would time out, which was fine; in fact, it is a very good thing, because GPS operation consumes current at 90mA, which is on the high side for a Psion Series 5. In the dark you need to turn on the backlight to make anything out at all, and the backlight is a little too bright and times out quicker than I would really like. You also should set it to turn on when the screen is pressed; this isn't a big deal for in car use, but is essential for use on a motorcycle.

The accuracy of the GPS is good enough that you can see your marker at least close to the road you should be on. Even on small back roads I could usually find the road that I was on in EnRoute's database, and had a reasonable idea of where to turn; the road lines don't indicate relative priority or right of way on the roads, but when you are driving and can see the next junction coming up, that isn't a problem.



EnRoute can show even very minor roads
EnRoute can show even very minor roads

My real objective was to use it on a motorbike; the car test showed that I was in with a good chance. The hard part is working out how to put the system together and still have it available for use; you don't want to have it at the bottom of a pannier or hidden in a back pack. You'll need a tank bag; I have an Oxford Products one with a set of magnets in the base to attach to a metal tank. For some reason my children think it makes an ideal fridge magnet, which is funny at first but soon palls. I don't object, because it means that I can find the bag whenever I need it, and it reduces the risk of accidentally trying to see if the magnets will pick up my credit cards, watch, phone and PDAs.

I put the GPS unit in the tank bag, and zip it up leaving just a small gap for the serial cable. This leads into a clear plastic bag holding the Psion; I use one of the dozens that seem to arrive at home every day covering free catalogues and magazines. A Series 5 fits very well into one of these; make sure that you fold over the end that the cable comes through, and don't pull the plastic too tight over it; you want some give in the plastic so that it doesn't cause any more problems than you will already have with fat fingers wrapped in gloves. Use plenty of duct tape to stick the plastic bag to the top of the tank bag; it sticks quite well if you have a transparent map holder as the top section of the bag, and you can reuse it if you are careful to not rip the bag when taking it all apart again.



the GPS/Psion tank bag ready to roll
the GPS/Psion tank bag ready to roll

As I said earlier, this setup, although situated on the top of your tank bag and only a couple of inches from your chin, isn't suitable for reading on the move. For one very good reason, it isn't safe to divert your attention when riding a bike. For another reason, the combination of bright sunlight and a helmet visor covered with bug guts makes the typical PDA screen very hard to read indeed. If you pull over to read it, so that you can concentrate on reading the screen, it isn't too bad. I did manage at first to fumble the brightness all the way down to black, but once I realised you have to press the increase brightness key combination lots of times rather than just hold it down, I managed to get over my panic!

It is much more advantageous than running the same set-up in a car, despite the difficulties. Navigating on a bike is hard work; to study a normal map you have to stop and partially unwrap your luggage, so looking at a PDA is easier than the normal course of events. It also eliminates the stop to take the map out of the tank bag and refold it to get onto the next section of map, which is a disaster waiting to happen on a wet and windy day.

Pilot GPS tester: http://www.GpsPilot.com/
Garmin: http://www.garmin.com
Mapper: http://3lib.ukonline.co.uk
Steve Lichfield's GPS notes: http://3lib.ukonline.co.uk/gpsnotes.htm
EnRoute: http://www.palmtop.nl



Words and design by:
Paul Lynch
Last updated: October 7, 1997

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