Thursday 25 November 2010

How Accurate Is The GPS?

Have you ever been asked "do you have a GPS?" whenever you asked for directions? Well, we have. It seems that almost everyone these days expect you to use the GPS to get you to your destination. 


But how accurate is the GPS? Can you totally rely on it to get you to where you want to go? Most of my friends who own one swear by it.


I have my doubts. I mean, well, the GPS would probably eventually take you where you want to go, but I believe there would be some inaccuracies. After all, it relies on the satellite signals, which I feel could be obstructed by tall buildings, huge trees or even the weather. Astro, our satellite TV, is a good example of how satellite signal is lost during a storm. Moreover, in KL, a junction where you could turn right might become illegal to turn the next day and the maps might not be updated right away.


So, hubby and I decided to conduct a little experiment over a period of two weeks. We decided to use the GPS on his mobile handphone to take us home from places we're totally familiar with. 


The result? If we had followed the instructions of the GPS, we would probably be going around in circles before we reached home.


The first test was from Bukit Bintang to Kepong. The instructions were correct only up to a point. At a junction, the GPS instructed us to turn right at a traffic light which does NOT allow any right turn. Due to the way the traffic lights were programmed, traffic has to move straight ahead and not turn right. Not unless we wish to crash into another vehicle, or have a vehicle smash into the left passenger side of our car. While we'd love to go to heaven, we don't want to die. So, we ignored the instruction.


As we followed the course of the road, the GPS started to 'recallibrate calculation'. And that was the message we were going to hear over and over again throughout the test as we ignored the GPS' instructions and headed in a different route. GPS, why should we turn off onto the NKVE highway to get to Kepong when we're already on Jalan Duta? No doubt we could get to Kepong via that route, but that would be driving off-course to the West to get to the North when we're already on the North. 


And in one of the tests from the "belly" of Pudu, the GPS misread our position and instead of directing us to turn right when we expected it to, it asked us to proceed straight for another few meters and then instructed us to turn right, smack into a building. Yes! It kept saying "Turn right now!". Well, no thank you, GPS, we have no desire to smash our brains against a wall. 


Undeterred, the GPS continued to try to direct this recalcitrant couple by instructing us to turn right when we came to a junction where there is a huge divider in the middle of the road. We have two options: either we smash into the divider, or we could drive against the traffic on our side of the road. No brains required to figure out which option we took. Neither.


So, what's wrong with the GPS? Initially, I thought that perhaps our maps aren't updated. But as the tests progressed, I realised that the GPS most likely had misread our position. It didn't know our precise location. Its signals were probably deflected or blocked by the tall buildings surrounding us for the times when the instructions were wrong, we were in a "belly" of buildings or underpasses.


To check if my hunch was correct, I googled and found that, indeed one of the disadvantages of the GPS is its inaccuracies. I found quite a few articles, but the article below sums it up.   http://www.ehow.co.uk/list_5912431_advantages-disadvantages-gps-systems.html