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

This draft explores the concepts of uncertainty and confidence in geolocation data, discussing their definitions, importance, and expression methods. It clarifies how errors are quantified using uncertainty and confidence values, emphasizing their significance in measurements. Additionally, it delves into Probability Density Functions and dispels myths regarding these terms. The document aims to enhance understanding and provide guidance on manipulating uncertainty and confidence in geolocation data, particularly in the PIDF-LO context.

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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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