Thanks guys, it was an excellent explanation, but don't you know something about the accuracy of the emulator? why it is little accurate?
On 18 Ago, 02:39, jdesbonnet <[email protected]> wrote: > Yes, 5 - 10 meters for regular consumer units is the simple answer. > In reality it varies depending on a few things: > > 1. Clear view of sky from all angles. If satellites are visible from > only one portion of sky then the triangulation does not work so well > and you get a high dilution of precision (see this article in > Wikipedia:http://en.wikipedia.org/wiki/Dilution_of_precision_(GPS) ) > 2. Solution from 4 or more satellites. The more the better. The unit > can make do with just 3 satellites if it guestimates your altitude: > but if the guess is wrong you can be off by whatever distance the > altitude is off. In one case I had my GPS on while in the air, then > switched it on while on the ground. I was off by several km until the > unit got a full 3D fix with 4+ satellites. > 3. Reflections of signals off buildings in urban areas causing errors > in the solution. I think modern units are good at mitigating that > problem. > > The reply below mentions deliberate error. Yes, that did exist once. > It was called SA (Selective Availability). Deliberate errors were > introduced into the clock signals and orbital parameters which ensured > an uncertainty of approx +/- 100m for civilian units. President Bill > Clinton ordered it switched off permanently in 2000. I caught the > moment in this graph:http://www.wombat.ie/gps/index.shtml > (Ironically SA was temporarily switched *off* in 1990 during Gulf War > I, because the military did not have enough military units). > > Timing is mentioned in the post below. GPS is excellent for getting > good time (+/- 1 microsecond of UTC is easily achievable with cheap > hardware). Time sync is such an important application of GPS that even > during the SA era, one satellite (# 13 if memory serves me correctly) > was guaranteed to have accurate timing signals at all times. > > Joe. > > On Aug 17, 3:32 pm, _AM_ <[email protected]> wrote: > > > > > Hi, > > > 5-10 miters is accuracy of GPS. Do not expect too much... > > > According to conspiracy theory this is done specially by USA > > military :) they each day set new deltas into GPS system to prevent it > > use for rockets navigation by other countries... > > > In reality I think GPS internal timing is not very good for making > > more accurate positioning. > > > On Aug 16, 5:38 pm,Lorenz<[email protected]> wrote: > > > > How much accurate are the coordinates received by the GPS antenna in > > > the reality?I'm using the emulator but it doesn't work well with > > > coordinates too much close...is there nobody that have tested an > > > application based on the package "Location" in a real device(I don't > > > have a real one yet..) and knows how to answer me?.. > > >Lorenz > > > > thanks! --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
