[Loadstone] Observations on Accuracy with Two Receivers

Kevin Chao g.unit89 at clearwire.net
Tue Oct 23 04:45:53 BST 2007


I actually have an equation that will give a fairly good reading in feet or
meters and is dependant on if there is a differential fix or regular fix.
This is an equation that is really straightforward and has been approved by
many experts in the field. This particular equation will not work with the
vdop reading and as far as I can tell there really isn't a reliable equation
that can give you an estimated accuracy of the vertical plane. It is just
too flakey and in order to get a stable reading for the vertical plane, it
will require for a satellite to be directly overhead. 

If you want the equation, send a message off-list. 

Kevin 

-----Original Message-----
From: loadstone-bounces at loadstone-gps.com
[mailto:loadstone-bounces at loadstone-gps.com] On Behalf Of Shawn Kirkpatrick
Sent: Monday, October 22, 2007 8:32 PM
To: loadstone at loadstone-gps.com
Subject: Re: [Loadstone] Observations on Accuracy with Two Receivers

There's talk about it somewhere on this list, I think someone pointed out a
wikipedia entry about it somewhere but I don't have the link at the moment. 
Getting exact information on how to do these calculations seems pretty much
impossible from what I can tell unless I'm not looking for the correct
information. The method we're using seems correct but who knows for sure. 
The accuracy values are just an estimate from the receiver anyway so that
could be off as well.

On Mon, 22 Oct 2007, Kevin Chao wrote:

> What is this user range error?
>
> I have read of various other equations and ones that require integrals 
> and simations, but not ones that use the "user range error."
>
> Kevin
>
> -----Original Message-----
> From: loadstone-bounces at loadstone-gps.com
> [mailto:loadstone-bounces at loadstone-gps.com] On Behalf Of Shawn 
> Kirkpatrick
> Sent: Monday, October 22, 2007 5:19 PM
> To: loadstone at loadstone-gps.com
> Subject: Re: [Loadstone] Observations on Accuracy with Two Receivers
>
> The equation for getting the accuracy in metres is to multiply the 
> hdop by the user range error setting. The same goes for the vertical 
> accuracy, multiply vdop by user range error. The conversion to feet is 
> done if the user has it set to use imperial. I'm not completely sure 
> if this is the correct equation but I think it is. Vertical accuracy 
> is a lot less accurate but that's up to the receiver.
>
> On Mon, 22 Oct 2007, Kevin Chao wrote:
>
>> I am sure that the hdop reading is taken into account when reporting 
>> the accuracy in number of feet.
>>
>> I am wondering what equation is the LoadStone team using to take the 
>> hdop value and giving the user a number of feet?
>>
>> Is there a similar equation that can be used for the vdop? I know 
>> that the vertical reading is a lot more flakey and less accurate, but 
>> just
> wondering.
>>
>>
>> Thanks,
>>
>> Kevin
>>
>> -----Original Message-----
>> From: loadstone-bounces at loadstone-gps.com
>> [mailto:loadstone-bounces at loadstone-gps.com] On Behalf Of Michael O.
>> Hanson
>> Sent: Monday, October 22, 2007 1:25 PM
>> To: loadstone at loadstone-gps.com
>> Subject: [Loadstone] Observations on Accuracy with Two Receivers
>>
>> Changing accuracy from a number to a number of feet was a great
> improvement.
>>
>> I don't want to start the great GPS receiver controversy or anything 
>> like that.
>>
>> Some users might find the information below helpful.  I do not claim 
>> that these test results are anything close to conclusive.  They are 
>> my observations.
>>
>> My testing was not performed under scientific or controlled conditions.
>> Other users could get vastly different results for any number of reasons.
>>
>> I tested a Holux M-2000 and a Royaltec RBT-2110.  I tested both 
>> receivers in my living room and outside.
>>
>> The Holux got average readings of between twenty and thirty feet.  
>> The lowest was 20.8 feet.  The highest was thirty feet.
>>
>> The Royaltec got readings of between fifty-five feet and ninety-four
feet.
>> The lowest was fifty-four feet.  The highest was ninety-six feet.
>>
>> The Holux averaged eight to ten out of twelve satellites.  The 
>> Royaltec averaged four out of twelve.
>>
>> I know the Royaltec is somewhat better at tracking direction changes.
>> It is a perfectly usable receiver in my experience.  If there is some 
>> factor I am not taking into account, please let me know.
>>
>>
>> Mike Hanson
>>
>>
>>
>>
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>>
>>
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