Example with shaded urban Example with shaded urban area: Davis, Californiaarea: Davis, California

Linear extentLinear extent-- Defined as Defined as the distance from the the distance from the geographic center of the geographic center of the location to the furthest point location to the furthest point of the geographic extent of of the geographic extent of the location.the location.

Locality Types: Named PlaceLocality Types: Named PlaceNamed PlaceNamed Place – Used to refer to traditional and non-traditional features – Used to refer to traditional and non-traditional features (towns, cities, mountains, ranches, highway mile markers, townships, (towns, cities, mountains, ranches, highway mile markers, townships, intersections). Use geographic center for the coordinates. intersections). Use geographic center for the coordinates.

Example: Jean, NevadaExample: Jean, Nevada

Named PlaceNamed Place – Small town – Small town

Locality Types - Named PlaceLocality Types - Named Place

Use the Use the error calculator to determine uncertainty

Locality Types:Locality Types: Named PlaceNamed Place – Lake, Mountain, – Lake, Mountain,

Cultural Land, or Other Cultural Land, or Other Geographic EntityGeographic Entity

““Mount Vesuvius, Italy”Mount Vesuvius, Italy”

Extent is usually half the length from Extent is usually half the length from the coordinates of the center of the the coordinates of the center of the named place to the furthest point named place to the furthest point within the named place.within the named place.

Named Place – Street AddressNamed Place – Street Address

““#10 Downing St., London, England”#10 Downing St., London, England”

Extent is the smallest area possible that cannot be mistaken Extent is the smallest area possible that cannot be mistaken for another address, sometimes ½ a city block.for another address, sometimes ½ a city block.

Locality Types:Locality Types:

Named Place – JunctionNamed Place – JunctionJunction of Hwy 80 and Hwy 9, Hidalgo, New MexicoJunction of Hwy 80 and Hwy 9, Hidalgo, New Mexico

Measure the extent of the junction as if it were a named place. Use the Measure the extent of the junction as if it were a named place. Use the following standards for extent: following standards for extent:

10 m for two lane city street or highway, 10 m for two lane city street or highway, 20 m for four lane highway20 m for four lane highway30 m for large highways with medians30 m for large highways with medians

Named Place – RemoteNamed Place – Remote

A locality that does not have a clear boundary on the map. A locality that does not have a clear boundary on the map.

Olancha, Olancha,

CaliforniaCalifornia

Extent is Extent is half the half the distance to distance to the center of the center of the next the next nearest nearest named named place place (or feature), (or feature), which is which is Grant, CA.Grant, CA.

Distance from a Distance from a named place using named place using the center of the the center of the named place as a named place as a starting point. Used starting point. Used with a heading to with a heading to give direction and give direction and distance from distance from named place.named place.

These can be with These can be with a direction, direction a direction, direction and distance, and distance, direction along a direction along a path, etc.path, etc.

Offsets:Offsets:““5 miles north of Beatty, on US 95”5 miles north of Beatty, on US 95”

Locality Types: Offsets by roadLocality Types: Offsets by road

Error is smaller for by road than by air (5.261 miles), as there is Error is smaller for by road than by air (5.261 miles), as there is no error in direction for offsets by road.no error in direction for offsets by road.

Remember uncertainty in extent, direction, distance, units, Remember uncertainty in extent, direction, distance, units, coordinate precisions and other factors all contribute to error.coordinate precisions and other factors all contribute to error.

Locality Types: Offsets by roadLocality Types: Offsets by road

Locality Types: Locality Types: Offsets using 2 cardinal directions by airOffsets using 2 cardinal directions by air

Specific Locality DecLat DecLong Extent MaxErrorDistance5.1 miles north and 2.1 miles east of Beatty 36.97949 -116.72151 1.4 2.132 mi

Error is smaller for both of these, compared to the error for one Error is smaller for both of these, compared to the error for one direction by air (5.261 miles).direction by air (5.261 miles).

Comparing OffsetsComparing Offsets

Georeferencing Error Calculator: Error onlyGeoreferencing Error Calculator: Error only0.3 km east by road of “Kilometer Zero”, Puerta del Sol, Madrid, España0.3 km east by road of “Kilometer Zero”, Puerta del Sol, Madrid, España

Georeferencing Calculator Examples

Locality:0.5 km N of Little mermaid, Copenhagen,

DK

Start with original coordinates for the mermaid:

55° 41' 34.18" N 12°35' 56.73" E

Then use the Georeferencing Error Calculator to determine the final coordinates AND the uncertainty.

Georeferencing Error Calculator:0.5 km N of Little mermaid, Copenhagen, DK

55° 41' 34.18" N 12° 35' 56.73" E

Georeferencing Error Calculator:Georeferencing Error Calculator:

Can be used to convert distances, including distances on Can be used to convert distances, including distances on maps (if the map scale is known). This is very helpful when maps (if the map scale is known). This is very helpful when georeferencing with paper maps.georeferencing with paper maps.

Capture georeferences in database or spreadsheet (we will use an Excel template for examples)

Georeferencing Templates