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It would be accurate to say that this presentation is presented by the .

Accuracy vs Precision. It would be accurate to say that this presentation is presented by the . However it would be more precise to provide more detail. For example, you could say that it is presented by an employee of

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It would be accurate to say that this presentation is presented by the .

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  1. Accuracy vs Precision • It would be accurate to say that this presentation is presented by the . • However it would be more precise to provide more detail. • For example, you could say that it is presented by an employee of • the namely Sherwyn Mack and that none of the stakeholders – including – would necessarily acknowledge any part in it or him. • (But this is an example of precision being overrated …)

  2. Accuracy vs Precision Accuracy vs Precision Disambiguated Accuracy A measure of how close a value is to the true value. Confusion with precision arises because we often describe them the same way “accurate to the within 100m” or “precise to the nearest second.” If I use this data, will I find what I’m looking for? Will I get close?

  3. Accuracy vs Precision Accuracy vs Precision Disambiguated Precision The level of detail contained in or described by the data. How small an area will the data take me to? Assuming the data is accurate, as described above, how close to the true location will it take me?

  4. Less Precise x Less Accurate More Accurate Accuracy vs Precision More Precise

  5. Accuracy vs Precision Groupings Precise, not accurate Accurate, not precise Precise and accurate Unlike in the previous slide, this graph doesn’t consider the size of the indicated area (dot). Rather, it focuses on the distance over which the points are spread as would be the case when studying species distribution patterns for example.

  6. X X X X X X X X X X X X

  7. Sources of Uncertainty

  8. Accuracy vs Precision

  9. Sources of Uncertainty allows for a high level of locality detail to be captured in addition to co-ordinates and information about the co-ordinates and how they were taken. However, this is only effective if the researcher in the field records data accurately and to a high level of detail. Thus a question that arises is how we (the ‘informatics people’) can get the researchers to be more detailed and objective in naming localities. (Don’t expect me to answer this one, I work in a basement.)

  10. Sources of Uncertainty

  11. Sources of Uncertainty

  12. Sources of Uncertainty • Coordinate Uncertainty • Map scale • The extent of the locality • GPS accuracy • Unknown datum • Imprecision in direction measurements • Imprecision in distance measurements (1km vs. 1.1 km) • Herman • Vusi • Sherwyn • Gillian • Mark • Bernard • Monica • Nosiphiwo • -hulle

  13. Sources of Uncertainty Use as many decimal places as given by the coordinate source for high precision. Seven decimal places = nearest meter. Decimal degrees given to five decimal places is more precise than degrees minutes seconds. False precision can result if data are converted from DMS to decimal degrees. Eg. 15˚ 20’ 20”  15.3388889 Record the GPS accuracy when saving a GPS waypoint. Be specific and objective when recording a locality name.

  14. Biologically unlikely Vague Non-sensical Requires specific knowledge Sources of Uncertainty

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