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Good and Bad Locality Descriptions

Learn the essential elements of a locality description, including elevation, coordinates, datum, and GPS accuracy. Discover tips to ensure your localities are specific, accurate, and easily understood. Examples illustrate good and bad locality descriptions to help you improve your georeferencing skills.

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Good and Bad Locality Descriptions

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  1. Good and Bad Locality Descriptions Elements and Examples

  2. Overview • Elements of a Locality • Verbatim Locality Description • Elevation • Coordinates • Datum • GPS Accuracy • Extent • Reference • Examples

  3. Less Precise More Precise x Less Accurate More Accurate What A Locality Should Be • Specific • Succinct • Unambiguous • Complete • Accurate • Precise

  4. Locality Tips • Avoid uncertainty due to imprecise headings • distance along a path • two orthogonal distances from a place • Use only one reference point • small in size (extent) • stable in position and size over time • easy to find on maps or in gazetteers • Avoid vague terms such as “near” and “center of”

  5. Elevation • Provide an elevation value • Beware elevation from GPS - it is less accurate than a barometric altimeter (when calibrated) • Report the source of elevation (map, altimeter, seat of pants, etc.)

  6. Coordinates • It is not enough to have coordinates alone, a locality description is essential. • Decimal degrees are recommended. If a different system is used, coordinate your resources. • More decimal places are better. • Original coordinates from GPS should be preserved for posterity.

  7. Datum • Datum has a corresponding coordinate system • Default datum WGS84 • Coordinate your resources, especially if you’re using a different datum • Coordinates without datum are ambiguous • Be consistent

  8. GPS Accuracy • GPS accuracy can be affected by many issues • number of satellites • interference • presence of reflective surfaces • Provide the GPS overall accuracy, or error, when possible • It will not be available later

  9. Extent • Indicates the size of the area within which an event (collection, observation) occurred • Can be a city, park, intersection, transect, grid, river, road, etc.

  10. References Document the sources and tools • Topographic map in field • Map title, publisher, scale, year, sheet number • Gazetteer or Road Atlas • Altimeter • GPS • Model • Datum • Accuracy

  11. Examples of Good and Bad Localities • Vague localities • BAD: “Sacramento River Delta” - an extremely large geographic areaBETTER: “Locke, Sacramento River Delta, Sacramento Co., California” - names a town within the Delta • BAD: “3 mi W of San Jose/Cartago border” - without additional details, this would mean anywhere 3 mi W of the borderGOOD: “3 mi W of San Jose/Cartago border on Highway 2, San Jose Province, Costa Rica”

  12. Examples of Good and Bad Localities • Names of Roads without additional reference • BAD: “Highway 9, Alajuela Province, Costa Rica” GOOD: “Intersection of Hwy 9 and Rio Cariblanco, Cariblanco (town), Alajuela Province, Costa Rica” • BAD: “S Berkeley, Alameda County, California”GOOD: “Oakland,1 mi S of intersection of 66th St and Telegraph Ave on Telegraph Ave., Alameda Co., California”

  13. Examples of Good and Bad Localities • Localities that are difficult to Georeference • BAD: “Battle Mountain, Lander Co., Nevada”BETTER: “Battle Mountain (city), Lander Co., Nevada” • BAD: “Km 58 Pan American Highway”GOOD: “Km 58 Pan American Highway, 6 km S of Cartago on Pan American Highway, Cartago Province, Costa Rica”

  14. REAL LOCALITIES FROM MaNIS Vague Biologically unlikely Non-sensical Requires specific knowledge To order Georeferencing T-shirt: http://herpnet.org/gbif/tshirt.html

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