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Uncertainty (draft-thomson-geopriv-uncertainty-00)

Uncertainty (draft-thomson-geopriv-uncertainty-00). IETF-70 Vancouver December 2007. Intent. Common definitions for uncertainty and confidence Why uncertainty and confidence exist How to express uncertainty and confidence Why uncertainty and confidence are important

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Uncertainty (draft-thomson-geopriv-uncertainty-00)

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  1. Uncertainty(draft-thomson-geopriv-uncertainty-00) IETF-70 Vancouver December 2007

  2. Intent • Common definitions for uncertainty and confidence • Why uncertainty and confidence exist • How to express uncertainty and confidence • Why uncertainty and confidence are important • How to manipulate uncertainty and confidence • Provide confidence in a PIDF-LO

  3. Quantitative vs. Qualitative Terms • Uncertainty and confidence are quantitative terms: • Have measurable values • Unambiguous meaning • Accuracy is a qualitative term • The location estimate is pretty accurate • Location estimate X is more accurate than location Y • There is no number or value that can be given to accuracy!

  4. What are uncertainty and confidence? • Errors occur from a range of sources when measuring any observable quantity • Errors are quantified using two values: • Uncertainty, which expresses the magnitude of the error, often a range • Confidence, the probability that the Target is actually in the specified uncertainty. • One without the other is meaningless

  5. Probability Density Functions (PDF) • Uncertainty + Confidence describe a probability density function • A function that expresses the probability that the target is at any particular point • Confidence is the area under the curve for a particular region • For a point, the area under curve is effectively zero, so… • For a point confidence is 0%!

  6. Civic Addresses • Civic addresses certainly expresses uncertainty • Effectively defined by the presence or absence of elements in the local hierarchy • Confidence is a little more difficult, default 95% confidence is recommended

  7. Dispelling a few myths • Uncertainty and confidence are not “Cellular” terms. • They are applicable to ALL measurements [ISO.GUM] • Confidence can’t be 100% • There is always a possibility of something being wrong

  8. What next? • PIDF-LO already provides uncertainty • Civic • Geoshape support in PIDF-LO profile • The WG needs a firmer grounding in terminology to progress

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