Re: [Geopriv] Text changes in 3825bis-08

["Bernard Aboba" <[e-mail]>]

Do we have agreement on a proposed text change for this sub-issue?

 

From: Richard L. Barnes [mailto:[e-mail]] 
Sent: Wednesday, February 10, 2010 3:37 PM
To: Thomson, Martin
Cc: Bernard Aboba; [e-mail]
Subject: Re: [Geopriv] Proposed text for 3825bis

 

Are you referring to the quantization error? 

     highvalue = value | mask
versus:

     highvalue = ( value | mask ) + 1 (== lowvalue + scale)

(the all-0xFF high value vs. the next low value)

 

If that's the concern, then we might as well just adjust the fixed-point
version to use the "+1" version.

 

I guess I'll agree that you're unlikely to get errors simply due to the fact
that you're doing floating-point arithmetic in this case.

 

--Richard

 

 

 

On Feb 10, 2010, at 3:21 PM, Thomson, Martin wrote:





The error is absolute (it's 2^-8 for altitude), it doesn't make sense to say
"up to".

 

From: Richard L. Barnes [mailto:[e-mail]] 
Sent: Thursday, 11 February 2010 10:16 AM
To: Thomson, Martin
Cc: Bernard Aboba; [e-mail]
Subject: Re: [Geopriv] Proposed text for 3825bis

 

Good point on the quantification: Suggested fix:

 

s/up to floating-point errors/up to a possible error of 2^-25/

 

 

 

On Feb 10, 2010, at 3:10 PM, Thomson, Martin wrote:






Hi Richard,

 

I notice that there is a small error in the first paragraph.

 

Section X: s/versions 1 and 2/versions 0 and 1/

 

I'll also note that the difference between setting bits and using exponents
of two is quantifiable.  The error in the upper value is 2^-25.