No subject

Thu Oct 18 04:18:40 BST 2007

it seems that the GPS reciever in general will send the lat/lon, altitude,
and speed at a rate of once a second. It is possible to tweak this update
rate and there are recievers that are designed to receive information once a
millisecond. There are receivers that have tried freezing the speed at
slower speeds, which have prooven to be useless at pedestrian speeds. It
would also be possible from the programmer stand point to average a set of
headings to smooth this multi-path issue, but it will take longer to obtain
na initial heading and and will take longer to update the heading once a
user has made a turn. There are always drawbacks. 


-----Original Message-----
From: loadstone-bounces at
[mailto:loadstone-bounces at] On Behalf Of Shawn Kirkpatrick
Sent: Monday, October 22, 2007 11:59 PM
To: LoadStone
Subject: Re: [Loadstone] better accuracy by position prediction

The position data from the receiver is usually only about a second behind,
maybe less. The speed data is maybe 2 seconds behind. I don't think there's
any way around this since you need some data to calculate speed. Since the
speed and position are both being provided by the receiver I doubt you could
use speed to correct position.
At some point there will be software calculations for heading and speed but
that'll be to correct for those receivers that have proven almost useless
for pedestrian use. Those receivers seem to give accurate position data
thoe. If we had another source of data then maybe correction factors could
be applied.

On Tue, 23 Oct 2007, Hasan Karahasan wrote:

> Hi folks,
> we all know that a gps based system takes some time to react on any
> When you are standing, yourr speed will be zero at optimal gps conditions.
> When you suddenly start to move, the system needs several seconds to 
> notice this and to offer the correct data. This happens to any change. 
> The receiver's data is always some seconds behind the real data. Can 
> we improve that indolent and sluggish behaviour by doing some 
> prediction? I am sure that commercial software does similar things. We 
> could do this by calculating an acceleration factor. While one thread 
> measures the speed and calculates the accelleration periodically, 
> another thread uses the result to correct the receiver's position 
> permanently. If speed is in an increasing state, we know that the real
position is more towards our current direction.
> We can add some meters to the receiver's position.
> If speed is decreasing, we can subtract something from the receiver's
> All loadstone functions would benefit from such a correction.
> What do you think about this?
> Hasan
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