im looking for a cheap gps or navman which does a good job mainly used for the speedo.
Cheap Navman GPS?
statman87 on 19/01/2012 - 17:16
Last edited 19/01/2012 - 17:17
Last edited 19/01/2012 - 17:17
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just watching today tonight last night when they said car speedos can be out and gps are correct to 99 percent
ERR…. Today Tonight is not exactly a reliable news source. They are known for sensationalist stories and dodgy reporting tactics. Same with A Current Affair.
Car speedos are generally more conservative from what I have heard (ie they report a slightly lower speed than your actual speed) but this will vary from manufacturer to manufacturer. and doesn't your speedo get checked when you service your car (I'm not sure about this though).
Really if you are that paranoid, then don't go faster than any of the cars on the road, as well as check your speedo once in a while and you will be fine. Another 'cheap'-ish alternative is if you have a smartphone, there are a swag of free speedometer apps out there that you can use.
cheers for that mate, but i was just thinking investing say $100 in a decent gps is saving alot in the long run if your speedos wrong and you get fined
GPSs also aren't exactly foolproof either. Go in a tunnel and you'll lose the signal. Also in the city, where there are heaps of tall buildings, you'll possibly lose the signal because you need a clear line to the sky.
Nothing is foolproof but have a bit of faith in your speedometer, and less in Today Tonight/ACA stories!
Well to be fair a decent GPS will cost you more towards the 200+ mark than ~100.
$100 won't get you decent GPS
cheers buddy
Sorry I hope I didn't sound too harsh there. I just get a bit annoyed when people take Today Tonight/ACA seriously!
Anyway you can get a cheap GPS for around the 100 mark - but these are the low end models, with a smaller screen (which can be a bit annoying).
Borrow a mate's GPS and compare the speeds for a good drive. You can have a good idea how reliable your speedo is by then
The problem I find with GPS displayed speeds is they aren't displayed to a single km/h. I regularly see my devices jump from 102 to 107km/h for example. At least you know roughly the range of speed that you are in, I think it is to do with rounding errors in the calculations. That's the disadvantage to "civilian" grade GPS, it's only accurate to 15 metres or something like that, the military grade ones are spot on, but you aren't allowed to have that (to prevent you using it on a homebrew guided missile)! I've manually checked my car on many occasions, measuring the circumference of tyres/checking air pressures/counting the teeth on the speedo gear sender, knowing the diff ratio etc. and doing the maths, and comparing it to GPS readings. I'm confident GPS is pretty reliable whenever you have a signal, within a couple of km/h. Wearing a couple of mm of rubber off your tyres can throw your speedo out a bit more than you think. I think most States have a tolerance for measuring your speed, like 3km/h or so to allow for variation in tyre circumference due to wear/pressure/heat or other speedo errors. I'd agree that the best thing to do is test your speedo against a GPS yourself and know how accurate it is. If it is way out (you've probably changed tyre size etc.), change the sender gear to suit for a few dollars. Speedo's are generally manufactured on the conservative side, my motorcycle was actually 10% under actual speed out of the factory. There are electronic devices that can alter the sender pulses and correct them to get an accurate reading if you have an electronic (not cable driven) speedo. (e.g. http://yellr.com/ or http://www.jaycar.com.au/productView.asp?ID=KC5435). I'm pretty sure no one checks speedos for accuracy when you have a car serviced, unless you put your car on a dynamometer or similar. The cheapest way to check is to steadily drive along a freeway at exactly 100km/h (use a cruise control if possible) and using a stopwatch, time the duration between kilometer signposts passing a fixed point of your car (the 'A' pillar around your windscreen for example). It should take exactly 36 seconds for one kilometer at that speed.
The bottom line is that you don't need to keep using a GPS to check your speed, borrow one and check your speedo once and get an idea how accurate it really is (unless you need a GPS for navigation of course). That's the OzBargain way — no need to waste money unnecessarily :)
statman87- Have you driven through speed checks on the road? I drive a Toyota and I have noticed that when I have my speed logged at 100km/hr and drive through speed checks on the freeway- it picks it up at 95-96.
Maybe you could try this and see how you speedometer reads I guess
We have 3 cars, I've noticed a speed difference. Two of our cars read 9km/hr faster at 100-110km/hr than the actual speed the car is traveling. But I think those two cars are designed that way as a safety feature.
BTW. When that story was on, and they said it's law that speedos are accurate - that was a pretty sweeping statement. It ignores the fact there are older cars on the road, and any accuracy law may not have been in existence when they were made. It also ignores the fact a speedo that reads faster than actual speed, is no big deal.
But anyway… I've used 3 different brand GPS's (two of them in the last couple of weeks) and I've not seen any jumping speed variations like someone mentioned. And if I was going to see it, I'm sure I would have - since one of those trips was 7 hours - and the other was from Bendigo VIC to Newcastle NSW - a drive of 1000km.
- One was a TomTom 1 (their cheapest model)
- One was a Navman (forget the model, but cheap again)
- One was a Navigon 1300 (again, a basic model)
If the only thing you want is to watch the speedo, you could buy one second hand on ebay, etc. If you want something good, wait a few weeks and buy the new Nuvi unit coming out by Garmin - when they have a "lifetime maps" offer on.
TomTom WERE good too… New map updates could be applied to all their previous models. But I read they've recently changed something, so new maps won't work on older models!? (I'm not certain on the specifics of this. But I probably read it on www.whirlpool.net.au)
What is wrong with your car's speedometer??