Spatial-> Vertical extent wording (again..)

[n-a-t-e]

Sadly I think the text for vertical direction in the metadata form is still a bit wrong, since it mentions sea level 😿

and EPSG doesnt mention sea level, probably because it can be used for depths in lakes as well, and we do have some lake data

We could change the example given: (i.e. a maximum value of 150m implies 150m below sea level the surface).

Definitions: https://epsg.io/5831 , https://epsg.io/5829

[JessyBarrette]

#190 is related to that issue.
Here's some more CF definitions:

• depth: Depth is the vertical distance below the surface.
• height: Height is the vertical distance above the surface.
  Surface is defined by the EPSG selected. ACDD has no default but we can always pick one:

From ACDD https://wiki.esipfed.org/Attribute_Convention_for_Data_Discovery_1-3

There is no default for this attribute when not specified. Examples: 'EPSG:5829' (instantaneous height above sea level), "EPSG:5831" (instantaneous depth below sea level), or 'EPSG:5703' (NAVD88 height).

[JessyBarrette]

Ideally the following fields should be available:

geospatial_bounds_vertical_crs	The vertical coordinate reference system (CRS) for the Z axis of the point coordinates in the geospatial_bounds attribute. This attribute cannot be used if the CRS in geospatial_bounds_crs is 3-dimensional; to use this attribute, geospatial_bounds_crs must exist and specify a 2D CRS. EPSG CRSs are strongly recommended. There is no default for this attribute when not specified. Examples: 'EPSG:5829' (instantaneous height above sea level), "EPSG:5831" (instantaneous depth below sea level), or 'EPSG:5703' (NAVD88 height).
geospatial_vertical_min	Describes the numerically smaller vertical limit; may be part of a 2- or 3-dimensional bounding region. See geospatial_vertical_positive and geospatial_vertical_units.
geospatial_vertical_max	Describes the numerically larger vertical limit; may be part of a 2- or 3-dimensional bounding region. See geospatial_vertical_positive and geospatial_vertical_units.
geospatial_vertical_positive	One of 'up' or 'down'. If up, vertical values are interpreted as 'altitude', with negative values corresponding to below the reference datum (e.g., under water). If down, vertical values are interpreted as 'depth', positive values correspond to below the reference datum. Note that if geospatial_vertical_positive is down ('depth' orientation), the geospatial_vertical_min attribute specifies the data's vertical location furthest from the earth's center, and the geospatial_vertical_max attribute specifies the location closest to the earth's center.

[n-a-t-e]

We will have vertical up/down relative to ocean surface (EPSG 5829/5831), we can add a third option to manually enter an EPSG for those who need that.