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#107: CF Data Model 1.7 -----------------------------+---------------------------------------------- Reporter: markh | Owner: [email protected] Type: task | Status: new Priority: medium | Milestone: Component: cf-conventions | Version: Resolution: | Keywords: -----------------------------+---------------------------------------------- Comment (by graybeal): I just lost a longer response that basically amounts to the same think Jon Blower just said. Stupid TRAC. I include a few references in case they help others. In short, it should be possible to convert from a 'depth wrt local sea level' to some other, more algorithmic CRS based on earth geoid or ellipsoid), but the error may be high, because local sea levels are more time variant than available sea level measurements or estimates. So while often there is not a precise 'distance from local sea level to the WGS84 ellipsoid for each depth measured', but there is a broader value (and sometimes there is even a precise value, as when moorings measure their GPS altitude). Definitions based on ISO: coordinate reference system (CRS): coordinate system + datum; types include geodetic and vertical coordinate system (CS): mathematical rules specifying how coordinates are assigned to points; composed of coordinate system axes; types of interest to use are ellipsoidal (earth shaped, 2D or 3D) and vertical, and the compound type datum: parameters to specify the relationship of a coordinate system to an object (Earth, in all our geospatial cases); defines position of origin, scale, and orientation of the CS (note that [13] references two definitions for datum, we are using ISO [7] for our reference definition) References: [7] Coordinate systems standards | ISO 19111 | ISO 19111.2007(E); for sale by ISO [13] Datums | geodetic datums FAQ | http://www.ngs.noaa.gov/faq This materially taken from previous work to consolidate CRS issues for OOI: https://confluence.oceanobservatories.org/display/CIDev/Coordinate+Systems+and+Coordinate+Transformations -- Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/107#comment:48> CF Metadata <http://cf-pcmdi.llnl.gov/> CF Metadata This message came from the CF Trac system. To unsubscribe, without unsubscribing to the regular cf-metadata list, send a message to "[email protected]" with "unsubscribe cf-metadata" in the body of your message.
