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[BUG] Why, unlike EnvO are Elevation (a length) and Depression (a geometrical object) conceptualized very differently in SWEET? #245

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Garybc opened this issue Mar 24, 2021 · 7 comments
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@Garybc
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Garybc commented Mar 24, 2021

A bug report assumes that you are not trying to introduced a new feature, but instead change an existing one... hopefully correcting some latent error in the process.

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@Garybc Garybc added the bug label Mar 24, 2021
@dr-shorthair
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Elevation is strictly not a length, it is a coordinate. It is defined as an offset with respect to a vertical datum, a spheroid, approximating the Geoid which varies with lateral position.

@dvaranka
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dvaranka commented Sep 13, 2021

The lowest point of a depression is an elevation as well and could be represented with a coordinate. A 'depression' is a geospatial feature that would include, I am guessing, other criteria for its definition as well (slope, size, etc). I think Gaurav uses the term 'eminence' as the antonym of 'depression.'

@Garybc
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Garybc commented Sep 14, 2021 via email

@dvaranka
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dvaranka commented Sep 14, 2021 via email

@rduerr
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rduerr commented Mar 15, 2023

If there are no other comments, I say we should make this change.

@Garybc
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Garybc commented Mar 15, 2023 via email

@smrgeoinfo
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looking at SWEET/depression in bioportal to try and understand what 'depression is supposed to be...

its a subclass of representation/numerical entity/geometrical object. The implication being that 'geometric object' is a representation of some geometry using numerical values. Then ... the subclasses of depression are 'basin' with a bunch of subclasses that are tectonic features-- kinds of sedimentary basins. The other subclass is 'depression' from the phenFluidDynamics namespace, a subclass of 'low pressure'-- which seems to me quite a different concept.

as @dr-shorthair pointed out, elevation is " an offset with respect to a vertical datum". In trying to understand 'depression' as a geometric object, it seems to require conceptualizing a surface that has an indentation in it, and that indentation ('depression') has some point of maximum offset relative to a datum defined by some relationship to the surface that is indented. You could think of that offset as an 'elevation' relative to the datum defined by the indented surface. So a depression in that sense has an 'elevation' property (although most would call it a depth).

Side bar about basin as a subclass of 'depression'
The kind of basin that has the enumerated subclasses in SWEET (a sedimentary basin) would have an older bounding surface that is a 'depression' relative to some datum-- something like sea level. But is a sedimentary basin this bounding surface, or the package of sediment deposited in the basin. Many active sedimentary basins have surface (physiographic) manifestations that are also 'depressions' in the topographic surface (think Basin and Range in the western US), but this is not a necessary property (think thrust belt foreland basins); inactive sedimentary basins in many cases are not manifested by a topographic 'depression' (Williston Basin, Michigan basin).

so... a geometrical object/depression might be a numerical representation of the geometry of the older bounding surface of a sedimentary basin. Sedimentary basins should not be subclasses of 'sweet:depression'. A similar line of reasoning would apply to meteorological atmospheric low-pressure 'depressions'

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