On Mon, Jul 19, 2021 at 12:12:09PM -0400, Christian Hopps wrote:
>
>
> > On Jul 17, 2021, at 7:24 PM, Benjamin Kaduk <[email protected]> wrote:
> >
> > On Sat, Jul 17, 2021 at 07:17:09PM -0400, Christian Hopps wrote:
> >>
> >>
> >>> On Jul 17, 2021, at 6:14 PM, Benjamin Kaduk <[email protected]> wrote:
> >>>
> >>> So, when we refine the coord-accuracy and height-accuracy for an
> >>> instantiation of the grouping, what does that mean?
> >>
> >> It’s supposed to mean the accuracy of the measurement that is recorded in
> >> the grouping. So if the coord-accuracy is .1 and the measurement is
> >> lat/long then the accuracy is within 1/10 of a decimal degree. if the
> >> measurement is in cart coordinates the accuracy would be 100cm. I don’t
> >> think we need to make this anymore complex than that. Is there some text
> >> you would like to see to make that clearer?
> >
> > The accuracy of the measurement with respect to what? The coordinate
> > system, or the actual physical object?
>
> I really don’t see how this could be so confusing.
>
> This grouping is a location, the accuracy applies to the contained location
> data. Consider asking this question about some other field like the lat/long
> — it doesn’t make sense.
It's confusing because there's a type mismatch between what the actual
words on the page say and what you're describing in the email thread.
> I can’t say for sure, but I think you’ve discarded the obvious here and are
> getting pedantic about something that’s not actually confusing.
>
> Finally, as we (the IETF) are not geo location experts, we had this grouping
> reviewed by actual industry experts (thanked in the acknowledgment section)
> and they had no issue with these fields. I would be very hesitant to change
> what they reviewed as correct at this point based on pedantic musings.
I'm confident that the actual fields in the model can provide the needed
information. We just need to clearly describe what information they are
conveying.
So, if we look at the
OLD:
leaf geodetic-datum {
type string {
pattern '[ -@\[-\^_-~]*';
}
description
"A geodetic-datum defining the meaning of latitude,
longitude and height. The default when the
astronomical body is 'earth' is 'wgs-84' which is
used by the Global Positioning System (GPS). The
ASCII value SHOULD have upper case converted to lower
case and not include control characters (i.e., values
32..64, and 91..126). The IANA registry further
restricts the value by converting all spaces (' ') to
dashes ('-')";
[...]
leaf coord-accuracy {
type decimal64 {
fraction-digits 6;
}
description
"The accuracy of the latitude longitude pair for
ellipsoidal coordinates, or the X, Y and Z components
for Cartesian coordinates. When coord-accuracy is
specified, it overrides the geodetic-datum implied
accuracy.";
}
this is indicating that the geodetic datum has some intrinsic default for
accuracy of latitude/longitude (not quoted, there is also some default for
height accuracy intrinsic to the geodetic datum).
If I were holding the pen, I might consider things like the following
NEW1:
leaf geodetic-datum {
type string {
pattern '[ -@\[-\^_-~]*';
}
description
"A geodetic-datum defining the meaning of latitude,
longitude and height. The default when the
astronomical body is 'earth' is 'wgs-84' which is
used by the Global Positioning System (GPS). The
ASCII value SHOULD have upper case converted to lower
case and not include control characters (i.e., values
32..64, and 91..126). The IANA registry further
restricts the value by converting all spaces (' ') to
dashes ('-')";
The specification for the geodetic-datum indicates
how accurately it models the astronomical body in
question, both for the "horizontal" latitude/longitude
coordinates and for height coordinates, typically as a
maximum deviation across the entire astronomical object.
NEW2:
leaf coord-accuracy {
type decimal64 {
fraction-digits 6;
}
description
"The accuracy of the latitude longitude pair for
ellipsoidal coordinates, or the X, Y and Z components
for Cartesian coordinates. When coord-accuracy is
specified, it overrides the geodetic-datum implied
accuracy. This might be used, for example, when the
particular coordinates in the sibling list of locations
are all located in a region of the astronomical object
where the model used by the geodetic-datum is a
particularly good representation of the actual
astronomical object";
}
NEW3:
leaf coord-accuracy {
type decimal64 {
fraction-digits 6;
}
description
"The accuracy of the latitude longitude pair for
ellipsoidal coordinates, or the X, Y and Z components
for Cartesian coordinates. When coord-accuracy is
specified, it indiates how precisely the coordinates in
the associated list of locations have been determined
with respect to the coordinate system defined by the
geodetic-datum. For example, this might be uncertainty
due to measurement error if an experimental measurement
was made to determine each location.";
}
In particular, what the actual words on the page are currently telling me
is what I think NEW2 says -- to "override" (or "refine") a given value
inherently must be of the same type as that value. What you've told me in
this email thread is more like NEW3, and if the NEW3 sense is intended,
then we shouldn't use the word "override".
-Ben
_______________________________________________
netmod mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/netmod
