UNCERTAINTY_NOT_SPECIFIED  AtlasOfLivingAustralia/aladataquality Wiki
Description
Uncertainty in metres was not supplied with the record.
Related fields
 dwc:decimalLatitude
 dwc:decimalLongitude
 dwc:verbatimLatitude
 dwc:verbatimLongitude
 dwc:verbatimCoordinates
 dwc:geodeticDatum
 dwc:coordinateUncertaintyInMeters
Implications and caveats
Severity: Warning
The uncertainty in metres value is defined as the radius (from the coordinates) of the smallest circle the location could fit within.
If this value is not supplied, it is difficult to know whether the occurrence happened exactly at the coordinates given, within 5 metres of the coordinates, within 50 metres of the coordinates or within an greater area. The level of accuracy may be important for various purposes, including the ongoing monitoring of an organism or determining the habitat of the organism.
This article provides information on the point radius method of georeferencing and estimating uncertainty: https://www.tandfonline.com/doi/pdf/10.1080/13658810412331280211
Where this value is not provided, or a very high value is provided, it indicates the accuracy of the coordinates may not be high.
Data custodian recommendations
If possible, provide a value for coordinate uncertainty in metres. This may be able to be determined from the methodology used to calculate the coordinates.
Code reference
ALAOccurrenceIssue.UNCERTAINTY_NOT_SPECIFIED
Discussion
Name  UNCERTAINTY_NOT_SPECIFIED 

Code  27 
Description  Uncertainty was not supplied with the record 
Severity/Verification/Metric  Warning 
Failure implication  See discussion below 
Revision Date  Extensively revised 28 October 2011 
How should we represent spatial uncertainty of occurrence records when precision and/or extent of location are not supplied?
Occurrence locations are typically represented using the point–radius method with latitude/longitude (DwC:decimalLatitude/DwC:decimalLongitude) being the centre point of the location, and coordinate uncertainty (DwC:coordinateUncertaintyInMeters) representing the radius of a circle that covers the whole location, including the extent of the location and ALL errors and uncertainties associated with determining the coordinates.
DwC:coordinateUncertaintyInMeters is exactly equivalent to Maximum Error Distance used in some georeferencing tools (J. Wieczorek in litt.).
In a typical Australian situation coordinateUncertaintyInMeters would often be calculated by adding the four following terms:
 extent of the location (ALA:locationExtent) – the radius of a circle encompassing the actual location or survey plot (not including other errors and uncertainties). Note that there is no explicit Darwin Core term for extent of location even though it is often included in the calculation of DwC:coordinateUncertaintyInMeters;
 uncertainty associated with geocoding method – this relates to GPS accuracy or scale of map used to determine coordinates;
 coordinate precision (DwC:coordinatePrecision)  the decimal representation of the precision of the coordinates, converted to metres;
 potential datum shift  where the datum (DwC:geodeticDatum) is unknown an additional error term needs to be added.
See example.
In Australia there has been considerable confusion regarding spatial precision and uncertainty, with the terms sometimes used interchangeably. DwC:coordinateUncertaintyInMeters has often been interpreted to be just the extent of the location, rather than the extent plus all other errors and uncertainties associated with determining the coordinates e.g. georeferencing method; DwC:coordinatePrecision and DwC:geodeticDatum. This confusion probably relates to there being no Darwin Core term for the actual extent of the location, and that the Darwin Core description of coordinateUncertaintyInMeters does not explicitly mention that is it is inclusive of all uncertainty metrics: "The horizontal distance (in meters) from the given decimalLatitude and decimalLongitude describing the smallest circle containing the whole of the Location. Leave the value empty if the uncertainty is unknown, cannot be estimated, or is not applicable (because there are no coordinates). Zero is not a valid value for this term".
With regard to spatial uncertainty, it is proposed that

Where recorded the extent of the location should be explicitly entered in a term new called locationExtent. Examples of location extent are the many millions of observational occurrences contained in the BA Bird Atlas data collected from 2ha, 500m and 5km survey plot locations, and historically from 10’ and one degree location grids. It is proposed that ALA nominated locationExtent be added as a term to the Darwin Core standard.

Where provided DwC:coordinatePrecision and DwC:coordinateUncertaintyInMeters (the overall metric) be also be saved as verbatim values in fields verbatimCoordinateUncertaintyInMeters and verbatimCoordonatePrecision. This will ensure consumers are aware of the original resolution of the data.

Where coordinates are generalized for the ALA Sensitive Data Service (typically by dropping decimal places from the coordinates, i.e. affecting the coordinatePrecision) then the Dwc:dataGeneralizations field be appropriately annotated; and DwC:coordinatePrecision and DwC:coordinateUncertaintyInMeters be adjusted thus:
Where verbatimCoordinateUncertaintyInMeters is explicitly available then:
DwC:coordinateUncertaintyInMeters = verbatimCoordinateUncertaintyInMeters and where coordinates are generalised by ALA then: DwC:coordinateUncertaintyInMeters = verbatimCoordinateUncertaintyInMeters + additional uncertainty from rounding coordinates, DwC:coordinatePrecision would be altered to relect the adjusted number of decimals.
Where DwC:coordinateUncertaintyInMeters is NOT available then:
DwC:coordinateUncertaintyInMeters is calculated by adding four nominal terms to represent overall uncertainty. The four nominal terms are (i) coordinate precision: the decimal representation of the precision of the coordinates, converted to metres (if not available label as ‘Unknown’ and substitute 150 metres); (ii) locationExtent: i.e. extent of the location (where location extent is not available label as ‘Unknown’ and substitute 1000 metres); (iii) potential datum shift: where the datum (DwC:geodeticDatum) is not available label as ‘Unknown’ and add an additional 200 metres. Do this also if the coordinates have not been projected to GDA 94 or WGS 84 coordinate system. (iv) geocode uncertainty : i.e. GPS accuracy or map scale uncertainty, an additional 150 metres
Therefore default DwC:coordinateUncertaintyInMetere = 150+1000+200+150 = 1500 metres
 Presently where uncertainty is specified some ALA spatial tools plot an uncertainty circle, while for visual clarity no circle is drawn when that field has an ‘Unknown’ value. Where this occurs there should be an explicit visual and textual indication that the location is in fact quite general and does not represent a point location.
It may be preferable that when the circle is shown it should represent the overall coordinateUncertaintyInMeters, and also be plotted when terms are ‘Unknown’. It would be worth conducting trials to obtain an optimal solution, perhaps with different shading/outline symbology where the terms are ‘Unknown’, e.g. if unknown a pale translucent circle with dotted outline could be plotted, while for specified values a darker circle with solid outline could be plotted.
Note: It may be possible to assign more appropriate substitute values for certain data sets, for example data from ALA ‘Share a Sighting’ tool could use a default coordinate precision of 0.00001 degrees or 2 metres, with the datum error as 0, and with the Coordinate uncertainty (extent) being defined by the user. Also, there is a trend to increased spatial precision through time, e.g. records in 1800's are generally much less precisely located than those geocoded today using GPS or Google maps.
A detailed explanation of each of the terms follows:
Overall Coordinate Uncertainty
Coordinate uncertainty (DwC:coordinateUncertaintyInMeters) represents the radius of a circle that covers the whole location, including the extent of the location and ALL errors and uncertainties associated with determining the coordinates. DwC:coordinateUncertaintyInMeters is exactly equivalent to Maximum Error Distance used in some georeferencing tools (J. Wieczorek in litt.). It is proposed that where altered the original values be displayed as verbatimCoordinateUncertiantyInMeters.
Uncertainty associated with geocoding method
These uncertainties generally relate to the method (DwC:georeferenceProtocol) used to determine the latitude and longitude. Generally coordinates determined from GPS are quite precise (510 metres), especially if the Horizontal Dilution of Precision (HDOP) is also recorded. Coordinates determined from modern satellite maps, for example, Google Maps/Earth are also quite precise (although beware of satellite image rectification issues). On the other hand coordinates determined from say 1:1,000,000 maps or from gazetteers presenting coordinates to one minute are much less precise. Where this values is unknown, generally substitute about 150 meters i.e. the approximate average error of reading geocode from a 1:100,000 to 1:250,000 map sheet.
Coordinate precision
The precision of the location is defined by DwC:coordinatePrecision ‘A decimal representation of the precision of the coordinates given in the decimalLatitude and decimalLongitude. Examples: "0.00001" (normal GPS limit for decimal degrees), "0.000278" (nearest second), "0.01667" (nearest minute), "1.0" (nearest degree)’.
Where coordinate precision is ‘Unknown’, generally substitute 0.001 degrees or about 150 metres.
Sometimes the coordinates are generalised to protect sensitive species locations. Common methods are to (i) round or truncate coordinates to fewer decimal places, (ii) grid the data or (iii) randomly move the location. Where altered the original values be displayed as verbatimCoordinatePrecsion. Any generalisations need to be factored into the overall coordinateUncertaintyInMeters.
It is important to note that the number of decimal places in the coordinates cannot be relied upon to explicitly indicate the precision of the coordinates as they are often (unknowingly) rounded, truncated and imprecisely transcribed.
Note that the conversion of coordinate precision to metres varies with latitude; see Guide to Best Practices for Georeferencing page 27.
Extent of the location: locationExtent
Where ‘Unknown’ generally substitute 1000 metres
The extent of the location is not presently defined in the Darwin Core standard, although is often used in the calculation of the overall spatial uncertainty, i.e. DwC:coordinateUncertaintyInMeters.
The extent of a location varies greatly, for example, it may be an actual point within a metre or two of the coordinate; it could be a general location such as Black Mountain Reserve which is about 3.2 km across (locationExtent of about 1600 metres); or it may be a standardised survey plot like the 2ha areas used by Birds Australia (locationExtent of 100 metres).
Geodetic datum and spatial reference system
Where ‘Unknown’ generally substitute 200 metres.
For a latitude/longitude coordinate to be precisely located you must also know the spatial reference system under which it was collected: DwC:geodeticDatum. The current global standard is WGS84 (used by GPS, Google Maps), with the Australian standard GDA94 being virtually identical. Coordinates collected under older Australian standards: AGD 1966 and 1984 are in a different physical location to those of the modern standards, and so may be mismapped by 200 metres if not accounted for (see http://www.icsm.gov.au/gda/mapsgda.pdf ). This potential inaccuracy is called datum shift. A fuller definition of the Spatial Reference System may be contained in DwC:verbatimSRS, but this is generally not needed if the datum is available.
References
Chapman, A.D and J. Wieczorek (eds). 2006. Guide to Best Practices for Georeferencing. Copenhagen: Global Biodiversity Information Facility. Available at http://manisnet.org/GeorefGuide.html
TDWG. 2009. Darwin Core Terms: A quick reference guide. Aaialable at http://rs.tdwg.org/dwc/terms/
Wieczorek, J. 2007 Georeferencing Calculator, Version 070228. Available at http://manisnet.org/gc.html, with guidelines at http://manisnet.org/GeorefGuide.html
Examples from Georeferencing Calculator, http://manisnet.org/gc.html for Charleville Qld (midway NS across Australia). MED is Maximum Error Distance aka coordinateUncertaintyInMeters (CUIM)
Assuming the location is an exact point:
Scenario  Geocoding method  Uncertainty from geocoding  Latitude  Longitude  Datum  Datum Shift (metres)  Coordinate precision (degrees)  Coordinate precision (metres)  Extent of Location  MED(m)  CUIM presentation (m) 

Google Earth (always WGS84)  Google Earth 10m accuracy  10  26.40066  146.24122  WGS84  0  0.00001  1.5  0  11.5  10 
Google Earth (always WGS84), and generalised to 2 decimal places  Google Earth 10m accuracy  10  26.4  146.24  WGS84  0  0.01  1500  0  1510  1500 
GPS, datum recorded  GPS 10m accuracy  10  26.40066  146.24122  WGS84  0  0.00001  1.5  0  11.5  10 
GPS, datum recorded, and generalised to 2 decimal places  GPS 10m accuracy  10  26.4  146.24  WGS84  0  0.01  1500  0  1510  1500 
GPS, datum unknown  GPS 10m accuracy  10  26.40066  146.24122  ?  200  0.00001  1.5  0  211.5  200 
GPS, datum unknown, and generalised to 2 decimal places  GPS 10m accuracy  10  26.4  146.24  ?  200  0.01  1500  0  1710  1500 
Bare coordinates 5 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.40066  146.24122  ?  200  0.00001  1.5  0  1201.5  1200 
Bare coordinates 4 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.4006  146.2412  ?  200  0.0001  15  0  1215  1200 
Bare coordinates 3 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.4  146.241  ?  200  0.001  150  0  1350  1500 
Bare coordinates 2 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.4  146.24  ?  200  0.01  1500  0  2700  3000 
Bare coordinates 1 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.4  146.2  ?  200  0.1  15000  0  16200  15000 
Bare coordinates 1 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26  146  ?  200  0  150000  0  151200  150000 
Assuming the location has an extent of 1000 metres (radius):
Scenario  Geocoding method  Uncertainty from geocoding  Latitude  Longitude  Datum  Datum Shift (metres)  Coordinate precision (degrees)  Coordinate precision (metres)  Extent of Location  MED(m)  CUIM presentation (m) 

Google Earth (always WGS84)  Google Earth 10m accuracy  10  26.40066  146.24122  WGS84  0  0.00001  1.5  1000  1011.5  1000 
Google Earth (always WGS84), and generalised to 2 decimal places  Google Earth 10m accuracy  10  26.4  146.24  WGS84  0  0.01  1500  1000  2510  2500 
GPS, datum recorded  GPS 10m accuracy  10  26.40066  146.24122  WGS84  0  0.00001  1.5  1000  1011.5  1000 
GPS, datum recorded, and generalised to 2 decimal places  GPS 10m accuracy  10  26.4  146.24  WGS84  0  0.01  1500  1000  2510  2500 
GPS, datum unknown  GPS 10m accuracy  10  26.40066  146.24122  ?  200  0.00001  1.5  1000  1211.5  1200 
GPS, datum unknown, and generalised to 2 decimal places  GPS 10m accuracy  10  26.4  146.24  ?  200  0.01  1500  1000  2710  3000 
Bare coordinates 5 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.40066  146.24122  ?  200  0.00001  1.5  1000  2201.5  2000 
Bare coordinates 4 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.4006  146.2412  ?  200  0.0001  15  1000  2215  2000 
Bare coordinates 3 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.4  146.241  ?  200  0.001  150  1000  2350  2500 
Bare coordinates 2 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.4  146.24  ?  200  0.01  1500  1000  3700  4000 
Bare coordinates 1 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26.4  146.2  ?  200  0.1  15000  1000  17200  15000 
Bare coordinates 1 decimals, assume geocoded from 1:1,000,000 map  1:1,000,000 map  1000  26  146  ?  200  0  150000  1000  152200  150000 
Note: CUD of earlier versions has been abandoned in favour of recording verbatimCoordinateUncertaintyInMeters and verbatimCoordinateArecision.
Replaces
uncertaintyNotSpecified