Tag Archives: GPS

We have two Garmins. Garmin A is a basic walker’s device called an “eTrex h” (the “h” is for high sensitivity). Garmin B is a nüvi something (and what’s that umlaut all about?) for our cars. A friend of mine has one of the earlier eTrex (no “h”) models which is quite prone to losing contact with the satellites when walking under any moderate tree canopy. Mine seems better so the “h” has apparently done some good. However, both GPS devices have trouble when I turn them on inside our house; they go into “acquiring satellites” mode and usually fail. The eTrex h even helpfully asks, “are you indoors?”

Now, the French are quite keen on building tunnels so that they can pile roads, particularly autoroutes, through mountains that have inconsiderately been thrown up by the forces of nature in the road engineers’ way. I appear to be able to drive through a 1km tunnel with hundreds of feet of rock above my head without the nüvi (what is that umlaut all about?) losing touch with the satellites; my track remains well plotted on the road.

If Garmin nüvi can’t see thrü (if you can’t beat ‘em, join ‘em) my skimpy roof tiles at home, how does it manage to see through a mountain?

Jüst cürioüs.

We’ve just returned from a walk in the company of our U3A friends. These walks are fortnightly gentle saunters, ~5m/8kms, through some very pleasant countryside and, this spring, in some very pleasant weather. We don’t usually know exactly how long a walk is ‘cos measuring them is a little tricky. In very distant scouting days, I’d have used a 1 inchOrdnance Survey map and a mechanical wheel device with which to trace the route and approximate its length. Given all the twists and turns on a 1″/mile map, though,  this was inevitably rather inaccurate.

Enter technology in the form of a Garmin eTrex h handheld GPS device. Apart from the archaic serial cable (see “GPS: Garmin Plain Silly”) required to download the eTrex’s information to a PC, a handheld device powered by two simple AA batteries that can track satellites sounds pretty high-tech, and I suppose in some ways it is. Mine even manages not to get lost under a fairly dense tree canopy – the “h” in eTrex h is something to do with high sensitivity. One companion, today’s leader, has an older eTrex (no “h”) which is constantly losing its signal under trees, so beware.

Looking for constructive uses for my toy, I thought it’d be interesting to measure some of our walks using Mr. Garmin. It’s also fun to download the route (through that archaic serial cable) – I use a piece of freeware called easyGPS – and subsequently display the route in Google Earth for added interest.

Given all the technology packed into satellite navigation systems and software development, you’d think that the resulting measurement of a walk would be spot on, would you not? Well, I would. After all, my Garmin nüvi satnav for the car tries to tell me precisely how fast I am travelling and “bongs” annoying warnings at me when I hit the speed limit, or, at least, the speed limit that it thinks exists which is frequently incorrect.

So, as we returned to our parked cars after a very enjoyable walk through some particularly fine countryside, several of our group chanted as one, “how far was that, John?” I pressed a few buttons to get the required answer from Mr. Garmin: 4.77 miles. Several walkers thought it felt longer but there you have it.

I got home (after a brief visit to a local hostelry) and downloaded the route using easyGPS: 5.23 miles.

I fired up Google Earth and sucked the saved .gpx file in to display the route on a simulated earth: 4.98 mile.

¿Que? That’s a variation of damn nearly ½ mile. Assuming that this walk must be approximately 5 miles, 0.5 mile represents a staggering 10% variation in all this wonderful technology. Since I still don’t know how long the walk actually was, I don’t know if I’ve got one accurate reading with two others having a 5% error or what. I do know that 10% over the speed limit can get you a ticket, though, so beware.

Maybe that old mechanical toothed measuring wheel on a 1” OS map wasn’t so bad after all. It certainly never broke down.

Today we spun over to Harwich to drop Keith and Marlene at the port where they were due to embark on Jewel of the Seas for their cruise through the Baltic Sea to Russia and back. There are times when I feel like the only person left on the planet that does not possess a satellite navigation device so our neighbour, Paul, had loaned us his Garmin unit with which to have a play. Not wishing to travel round the M25 ‘cos of horrendous road works, we set the unit to “shortest route” (the only alternative to “fastest route”, i.e. M25 – yeah, right) and set off.

“Play” proved to be accurate. The cross-country route was fun. We soon became curious as to why we were being warned of certain speed limits but not of others, especially as one of said “others” had a mobile speed camera lurking within it. These “others” were old, long-standing 30s and 40s so it certainly wasn’t a case of the unit not having been updated with recently changed information, they just didn’t seem to be there. By the time we’d covered a mere 30 miles or so we’d been through at least 6 speed limits with no technological notification, quite enough for any testosterone-rich Subaru Impreza WRX driver to have lost his license. [Ed: Hey, maybe that’s no bad thing!] Not that speed limits should be a satnav’s primary function but one clearly wouldn’t want to rely on one of these things for speed limit notification. I, of course, do not drive a Subaru Impreza WRX and I do look for road signs.

Once beyond Stansted, around which traffic seemed strangely light, we ran into the other automatic navigation issue which I’ve long suspected: “shortest route” is useless. At least, for cars it’s utterly pointless; it may be OK for bicycles and pedestrians. “Shortest route” completely ignores sensible, helpful bypasses and attempts to slam you straight through the very centre of large towns. After all, the shortest distance between two points is a straight line and that is what you asked for, isn’t it? Not good. What is really needed for cars is a “shortest sensible route” option. Unlike most of Joe Public, not having switched off our brains, we invoked the human-override option and took over. “Recalculating!” Garmin adjusted after getting only slightly pissy.

On our return journey from Shotley, we thought we’d try “fastest route”. We were routed initially to the A14, our normal, chosen-by-a-rational-human route.  After one measly junction, however, Garmin wanted us to turn south on the A12. Clearly, it was trying to get us on the disastrous northern section of the M25. We refused and kept on the A14. “Recalculating!” It’s quite amazing how intently Garmin wants you to get on motorways, particularly the M25. “Exit left and make a U-turn”. Normally, of course, I’m quite prepared to admit that this strategy works but the current plethora of road works definitely overrides normality. Again we ignored the advice. “Exit left and make a U-turn.” For two or three further junctions Garmin kept trying to make us exit, U-turn and retrace our steps back to the A12/M25 option. we continued to ignore it and eventually it did decide to head towards Bury St. Edmunds. “Recalculating! Continue for 41 miles.”

I don’t ever remember having as much fun in a car with my clothes still on. Garmin proved most entertaining and much better than any modern comedy show for raising smiles. I suspect that satnavs are quite handy for finding addresses in towns. I also suspect they’d be quite helpful when driving solo, map reading not being a legal option. They are easily trumped, however, when the navigator’s seat is occupied by someone with a decent map and at least half a brain. This configuration enables the pilot to keep an eye out for those pesky speed limit signs that the satnav keeps missing.

Guilty as charged, though they could be worth it for the pure entertainment value. I may get one anyway.

Having returned from Spain on Sunday to some pretty standard English drizzle, Monday and Tuesday were very pleasant, even if a little cool. Tuesday was our day for a U3A walk so I took the ol’ Garmin GPS along to plot our route. You can’t beat having a toy to add interest, can you? We may have had two days of dry, relatively sunny weather above ground but given the huge amounts of rain and snow that have been falling on England this winter, conditions underfoot  were still bound to be disturbingly muddy.

Muddy they were, definitely a job for walking boots. I much prefer walking in dry, dusty climates where I can concentrate on the scenery. I’m frequently told that England “is a green and pleasant land”. I wouldn’t argue with that assessment but I do get a little frustrated at not being able to admire said “green and pleasant landscape” because all my concentration is taken up not slipping and falling ignominiously face-down in the mud. Nonetheless, the company was good and the pint in the pub afterwards was good.

Our circuit began and ended in Wiggington, near Tring. The GPS claimed it to have been 5 miles. When I connected the GPS to my desktop at home and downloaded the route into easyGPS, that thought it was 5.19 miles. Because of the two steps forward and one step back situation courtesy of the mud, most folks’ legs thought it was considerably further.

Just for fun (and because I can), here is a Google Earth .kmz file of our cool but sunny day out. Assuming you actually have Google Earth, clicking on it should fire it up and display our wander. (The B### waymarks are bridges on the Grand Union Canal.)