Original Message From: Ginzbarg, Steve Sent: Thursday, August 13, 2009 3:23 PM To: 'tuco@berkeley.edu' Subject: RE: [tdwgcontent] dwc
John,
That's better. Some other possible wordings below.
Original Message From: gtuco.btuco@gmail.com [mailto:gtuco.btuco@gmail.com] On Behalf Of John R. WIECZOREK Sent: Thursday, August 13, 2009 11:37 AM To: Ginzbarg, Steve Subject: Re: [tdwgcontent] dwc
Thanks for your tenacity and patience, Steve.
I see what you are saying now. For the distances from surface, there is nothing saying explicitly what the nearest surface actually is. Is it the surface defined by the elevation or the surface defined by the depth?
I think this can be resolved by the following change in definition for minimumDistanceAboveSurfaceInMeters from:
"The lesser distance in a range of distance from the nearest surface in the vertical direction (positive for above, negative for below), in meters."
to:
"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."
[Steve Ginzbarg] or
"The lesser distance in a range of distance from a reference surface, either on land or underwater, in the vertical direction, in meters. Use positive values for locations above the surface, negative values for locations below."
or
"The lesser distance in a range of distance from a reference surface, either a land/air or a land/water interface, in the vertical direction, in meters. Use positive values for locations above the surface, negative values for locations below."
A similar change would apply to the maximumDistanceAboveSurfaceInMeters.
For coordinateUncertaintyInMeters I think we can solve the problem with the following simple change from:
"The upper limit of the distance (in meters) from the given decimalLatitude and decimalLongitude describing a circle within which the whole of the Location is contained. 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."
to:
"The horizontal distance (in meters) from the given decimalLatitude and decimalLongitude describing a circle within which the whole of the Location is contained. 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."
[Steve Ginzbarg] That's better. I think "smallest circle" is understood.
or, more explicitly,
"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."
Would these be satisfactory changes?
[Steve Ginzbarg] Yes.
I had a hard time finding the link on the webpage to all the terms and definitions, http://rs.tdwg.org/dwc/terms/.
John
On Wed, Aug 12, 2009 at 3:33 PM, Ginzbarg, Stevesginzbar@biology.as.ua.edu wrote:
Hi John,
Term Name: minimumDistanceAboveSurfaceInMeters
Definition: The lesser distance in a range of distance from the nearest surface in the vertical direction (positive for above, negative for below), in meters.
Comment: Example: 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", MinumumDepthInMeters: "20", MaximumDepthInMeters: "20", DistanceAboveSurfaceInMetersMinimum: "0", DistanceAboveSurfaceInMetersMaximum: "1.5".
Those would be the distances above the surface if the core was raised to the surface of the water. If it was still in place the numbers would be: Example: 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", MinumumDepthInMeters: "20", MaximumDepthInMeters: "20", DistanceAboveSurfaceInMetersMinimum: "21.5", DistanceAboveSurfaceInMetersMaximum: "20".
Explanation: The nearest surface in the example is the bottom of the lake, therefore the example is correct.
ditto maximumDistanceAboveSurfaceInMeters
Given the "to the nearest surface" part of the definition, these terms are not redundant; they were defined specifically to address the problem of more than one offset from a vertical datum.
[Steve Ginzbarg] It may be clear to the person recording the data which surface is the nearest but how is the person interpreting the data to know which surface was nearest, e.g. the surface of the water or the surface of the bottom of the lake?
Term Name: coordinateUncertaintyInMeters
Definition: The upper limit of the distance (in meters) from the given decimalLatitude and decimalLongitude describing a circle within which the whole of the Location is contained. 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.
change "upper limit" to "lower limit"
The coordinateUncertaintyInMeters is the maximum error distance as defined in the GBIF Best Practices. It is definitely the upper limit, not the lower limit.
[Steve Ginzbarg] Maximum error  we could be off by at most this much; but the shortest radius that describes a circle that contains the whole location. (An infinite radius would describe a circle that contains the location. We're looking for the smallest radius whose circle still does.
Steve Ginzbarg
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Ginzbarg, Steve