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Mitsubishi 4WD Owners Club of Qld (Inc) |
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GPS - Part 4 |
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GPS-101 Part 4 (Tracks and PC Software) First, a quick update on high sensitivity GPS Receivers. In a previous article, I mentioned the SiRFstarIII as being one of the most sensitive GPS chipsets. Other similarly sensitive chipsets (that’s the GPS engine inside your GPS unit), include: Fujitsu MB87Q2040 / MB15H156 Rfmd (30 Channel) MediaTek MT3318 (32 channel) These are often incorporated into other modules that are then incorporated into the GPS Unit. What you’re looking for is sensitivity down around the ‑157 to ‑160dBm range and the ability to track 20 or more satellites. Normal 12 channel receivers have a sensitivity around ‑143dBm. OK – so on to this month’s topics, Tracks and GPS PC Software. Let’s start with the latter. There are quite a number of PC software packages out there that will interface to your GPS unit. They range in price from free up to hundreds of dollars and have varying lists of functionality. The simplest ones just allow you to upload and download the Waypoints, Routes, and Tracks to and from your GPS. This is very useful by itself. The more advanced software allows you to overlay all of this GPS Data onto calibrated maps. Have a look here for a variety of software: http://www.gpsoz.com.au/links.htm. The software that I use mostly is OziExplorer. This is a great piece of software, because it allows you to overlay your Waypoints, Routes and Tracks onto maps. These can be maps that you scan and calibrate yourself, or purchased maps from Hema, SunMap, Auslig, etc. You can also create Waypoints, Routes and Tracks in OziExplorer and upload them to your GPS, or rename Waypoints that you have recorded on your GPS. This is a lot easier to do with a full size keyboard on your PC, than using the up and down arrows to change one character at a time in a waypoint name on your GPS. Another advantage of OziExplorer is that it is also available for PDAs, which are a lot easier to mount on your dashboard than a full size laptop computer. The PDA version, OziExplorerCE, uses the same map files as the PC version, but you may have to run a utility to convert the map image files to a format that is suitable for OziCE. This then allows you to have a moving map on your dashboard. Many GPS units have built-in maps, and you can generally buy more maps (at exorbitant prices) from Garmin, Magellin, and the like. There are some non-proprietary maps available for these units, in-fact I used the Tracks4Australia maps on my Garmin on the Heads and Tails Weekend (http://www.gpsoz.com.au/tracks4australia/). You can create your own maps for Garmin GPS units using software from the internet. It is a laborious process. I’ve done it, and I don’t do it any more. I’ll get into the difference between Raster Maps (The sort you use on OxiExplorer) and Vector Maps (The sort that you get from Garmin, or Magellin, etc) another time. Let’s start talking about Tracks while I’ve still got your attention. You are still there, aren’t you? – Good! Phew – I thought you might have wandered off to Swap and Sell, or Kamper’s Kitchen. The track functions on the GPS and OziExplorer is what I use most of all these days. Here’s the process that I use: Open up the maps in OziExplorer of the places you want to go. Create some tracks for your reccy in OziExplorer (The plan of the tracks that you want to check-out). I usually mark the intersections or turns too, as discussed below. Upload these tracks to your GPS (or PDA if you’re running one). Now you’ve got a wiggly line on your GPS that you can follow along your intended path. Do your reccy and record the actual tracks that you take. This will be impossible if your GPS only allows one track. You need either: a. A GPS that supports more than one track; b. A PDA connected to the GPS to record the actual track taken, while you follow the intended track on your GPS; c. A PDA connected to your GPS to display the intended track, while you record the actual track on your GPS; or d. 2 GPS units. When you’ve finished your reccy, download the actual tracks from your GPS to your computer. Now you can do the final plans for your trip. The actual track points, as well as storing the location of each point, stores the time you were there. This is really useful when you’re trying to work out distances along the track or the travel times from one place to another on your trip. Now you can copy bits of your recorded tracks together for your actual trip. Upload the final trip plan tracks to your GPS. Follow the wiggly line. NB. Whatever you do, when you’re doing a reccy for a trip, or running a trip, ALWAYS have paper maps, a compass, and a scale-rule, in case your technology fails. Remember the Platypus Creek Trip from last month. Here’s what I’d do in plotting a track rather than using waypoints. The planned track is marked over the top of the road as a thick dotted line. Notice how I run the tracks past the intersection so that you know the intersections are there. If you’re using a GPS without maps, then all you get to see is the wiggly line, not the other features, as shown in the second diagram. Having a wiggly line to follow on your GPS or PDA gets around the problem that I described in last month’s issue of the straight lines between waypoints. Once you start to use Tracks, you’ll find that you don’t tend to use Waypoints as much. These days, I tend to only use waypoints for major en-route destinations and use the Navigate Route function to give me a constantly updated distance (as the crow flies) and estimated time to these major points. In the next article I’ll start to cover “Maps on GPS Units”. Happy navigating. Greg Conlon |
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