DwC Mapping - MIXS:? alt

[tucotuco]

Field	Value
subject_id	http://rs.tdwg.org/dwc/terms/minimumDistanceAboveSurfaceInMeters
subject_definition	The lesser distance in a range of distance from a reference surface in the vertical direction, in meters. Use positive values for locations above the surface, negative values for locations below. If depth measures are given, the reference surface is the location given by the depth, otherwise the reference surface is the location given by the elevation.
subject_usage_notes
subject_examples	-1.5 (below the surface). 4.2 (above the surface). For a 1.5 meter sediment core from the bottom of a lake (at depth 20m) at 300m elevation: verbatimElevation: 300m minimumElevationInMeters: 300, maximumElevationInMeters: 300, verbatimDepth: 20m, minimumDepthInMeters: 20, maximumDepthInMeters: 20, minimumDistanceAboveSurfaceInMeters: 0, maximumDistanceAboveSurfaceInMeters: -1.5.
predicate_id	skos:narrowMatch
object_id	None given
object_label	alt
object definition	Altitude is a term used to identify heights of objects such as airplanes, space shuttles, rockets, atmospheric balloons and heights of places such as atmospheric layers and clouds. It is used to measure the height of an object which is above the earth’s surface. In this context, the altitude measurement is the vertical distance between the earth's surface above sea level and the sampled position in the air
object source	https://github.com/GenomicsStandardsConsortium/mixs-legacy/blob/master/mixs5/mixs_v5.xlsx
comment	A range of altitude can be captured in the combination of the terms dwc:minimumDistanceAboveSurfaceInMeters and dwc:maximumDistanceAbveSurfaceInMeters. If a single value is given, the same value should be used in both DwC terms.

and

Field	Value
subject_id	http://rs.tdwg.org/dwc/terms/maximumDistanceAboveSurfaceInMeters
subject_definition	The greater distance in a range of distance from a reference surface in the vertical direction, in meters. Use positive values for locations above the surface, negative values for locations below. If depth measures are given, the reference surface is the location given by the depth, otherwise the reference surface is the location given by the elevation.
subject_usage_notes
subject_examples	-1.5 (below the surface). 4.2 (above the surface). For a 1.5 meter sediment core from the bottom of a lake (at depth 20m) at 300m elevation: verbatimElevation: 300m minimumElevationInMeters: 300, maximumElevationInMeters: 300, verbatimDepth: 20m, minimumDepthInMeters: 20, maximumDepthInMeters: 20, minimumDistanceAboveSurfaceInMeters: 0, maximumDistanceAboveSurfaceInMeters: -1.5.
predicate_id	skos:narrowMatch
object_id	None given
object_label	alt
object definition	Altitude is a term used to identify heights of objects such as airplanes, space shuttles, rockets, atmospheric balloons and heights of places such as atmospheric layers and clouds. It is used to measure the height of an object which is above the earth’s surface. In this context, the altitude measurement is the vertical distance between the earth's surface above sea level and the sampled position in the air
object source	https://github.com/GenomicsStandardsConsortium/mixs-legacy/blob/master/mixs5/mixs_v5.xlsx
comment	A range of altitude can be captured in the combination of the terms dwc:minimumDistanceAboveSurfaceInMeters and dwc:maximumDistanceAbveSurfaceInMeters. If a single value is given, the same value should be used in both DwC terms.

[raissameyer]

In the beta version of MIxS V6, that @wdduncan linked to in issue #11, the unique MIxS ID for alt is given as MIXS:0000094 (IRIs reserved but not yet live), which we can use for future mappings.

[timrobertson100]

IRIs reserved but not yet live

Can you please explain what this means? Reserved where and how, please?

[wdduncan]

@timrobertson100 The IRIs listed for the terms listed in the MIxS 6 spreadsheet

E.g. The term alt (row 9 on the MIxS6 Core - to edit tab) has the IRI MIXS:0000094 in column AD. However, the IRI has not been registered with w3id.org. So, it will not resolve in a web browser.

Does that answer your question?

[timrobertson100]

Thanks @wdduncan

w3id.org was the bit that was missing for us. If I understand this correctly, they aren't IRIs yet but will be when prefixed by the resolving infrastructure they provide.

[wdduncan]

Update:
I run a report to verify that definitions for the same term (as identified by the IRI) are the same across packages. I am waiting until MIxS 6 has been finalized before running this report again.

[raissameyer]

How do we handle that the definitions of dwc:verbatimElevation, dwc:minimumElevationInMeters, dwc:maximumElevationInMeters also refer to altitude?

[...] elevation (altitude, usually above sea level) [...]

Should this be captured in the mapping?

[tucotuco]

The Darwin Core is in accord with the Georeferencing Quick Reference Guide where the definitions of the two terms are:

Elevation - A measurement of the vertical distance of a land or water surface above a vertical datum. On maps, the reference datum is generally some interpretation of mean sea level or the geoid, while in devices using GPS/GNSS, the reference datum is the ellipsoid of the geodetic datum to which the GPS unit is configured, though the device may make corrections to report the elevation above mean sea level or the geoid. Elevations that are above a reference point should be expressed as positive numbers, while those below should be negative. Compare depth, distance above surface, and altitude.

Altitude - A measurement of the vertical distance above a vertical datum, usually mean sea level or geoid. For points on the surface of the Earth, altitude is synonymous with elevation.

[tucotuco]

The relationships between the three vertical distance concepts is explained in detail at

https://docs.gbif.org/georeferencing-best-practices/1.0/en/#elements-distance-above-surface

[raissameyer]

Suggested syntax predicates for the mappings above https://github.com/tdwg/gbwg/issues/14#issue-805153888

Field	Value
subject_id	http://rs.tdwg.org/dwc/terms/minimumDistanceAboveSurfaceInMeters
subject_value_syntax - expected_value - unit	{float} / {float} {unit}- measurement value - meter
syntax_predicate_id	skos:narrowMatch
object_id	None given (alt)
object_value_syntax - expected_value - unit	{float} {unit} - measurement value - meter
syntax_comment	Not sure, MIxS expects {float} {unit}, DwC gives examples for both - {float} and {float} {unit}

and

Field	Value
subject_id	http://rs.tdwg.org/dwc/terms/maximumDistanceAboveSurfaceInMeters
subject_value_syntax - expected_value - unit	{float} / {float} {unit}- measurement value - meter
syntax_predicate_id	skos:narrowMatch
object_id	None given (alt)
object_value_syntax - expected_value - unit	{float} {unit} - measurement value - meter
syntax_comment	Not sure, MIxS expects {float} {unit}, DwC gives examples for both - {float} and {float} {unit}