Re: [netmod] Benjamin Kaduk's Discuss on draft-ietf-netmod-geo-location-08: (with DISCUSS and COMMENT)
Hi Christian, Sorry for the very delayed reply (and thanks to Rob for the nudge). On Wed, May 26, 2021 at 06:04:58PM -0400, Christian Hopps wrote: > > Benjamin Kaduk via Datatracker writes: > > > Benjamin Kaduk has entered the following ballot position for > > draft-ietf-netmod-geo-location-08: Discuss > > > > When responding, please keep the subject line intact and reply to all > > email addresses included in the To and CC lines. (Feel free to cut this > > introductory paragraph, however.) > > > > > > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html > > for more information about DISCUSS and COMMENT positions. > > > > > > The document, along with other ballot positions, can be found here: > > https://datatracker.ietf.org/doc/draft-ietf-netmod-geo-location/ > > > > > > > > -- > > DISCUSS: > > -- > > > > I think we lack sufficient precision (forgive the pun) in how we talk > > about "accuracy" and "precision". Are the leafs that claim to specify > > "accuracy" specifying a precision? If so, the precision of a specific > > measurement, the precision of the measurements that led to the creation > > of the coordinate frame, or something else? Are they doing so in > > relative terms (e.g., percentage) or absolute terms (e.g., degrees and > > meters)? (There are "units" directives only for "height-accuracy" and > > not the others.) How can we we say that we'll have 16 fraction-digits of > > precision for lat/long when the maximum accuracy we can say that a > > geodetic-system has only gives us 6 fraction-digits for coord-accuracy? > > When we say that the "precision of this measurement is indicated by the > > reference-frame" is that the same thing as the relevant "-accuracy" > > nodes, or something else? > > Yes, the geodesic-datum is what defines the values and their accuracy. For > the precision in the value we choose the fractional digits based on what > might be needed, but not to prescribe anything. For decimal degrees e.g., we > only need 100s values the rest can be left to the fractional portion. Unfortunately, even your description here still doesn't help me understand what the intended semantics of these values are. To help illustrate my confusion, here are a few possible things that could be what is intended to be conveyed: - the geodetic-datum description of the object has been measured to be within a known delta of the actual object being described, at all points on the object that the coordinate system can describe - the geodetic-datum description of the object is capable of determining relative differences between points on the object to within a particular delta of precision, but those individual coordinate values may be farther than that delta from the actual point on the object that was referred to - the values that are reported in this YANG module reflect measurements that were made and are known to be within some delta of the coordinate system's value that they are reported as - the values that are reported in this YANG module reflect measurements thare are known to be distinguishable from other measurements to within some delta of other measurements relative to that coordinate system, even though the actual position being indicated may diverge from the reported value by more than that delta - the values that are reported in this YANG module reflect measurements that were made and are known to be within some delta of the actual point on the object that the coordinates refer to - the values that are reported in this YANG module reflect measurements that were and are known to be distinguishable from other measurements of points on that object within some delta, but the actual distance from the measured point to the point on the object indicated by the reported coordinates may be larger than that delta In short, there are at least three classes of things at play here: the actual object itself, the coordinate system used to model the object, and values reported in the YANG module (which are assumed to ultimately derive from some form of measurement). To talk about accuracy or precision implies a relationship between elements of two of those classes, and I don't even know which of those classes you're trying to talk about. > > -- > > COMMENT: > > -- > > > > (I support Roman's Discuss.) > > > > Why do we only define velocity in terms of north/east/up, when we could > > be in x/y/z coordinates where there is no clear "north" or "east"? > > > > It would have been helpful for the shepherd review to point to the > > thread at > > https://mailarchive.ietf.org/arch/msg/netmod/dA9olZfEVa3clGdfvNYEFXUEMJw/ > > that attempted to discuss the feedback from the
Re: [netmod] Benjamin Kaduk's Discuss on draft-ietf-netmod-geo-location-08: (with DISCUSS and COMMENT)
Benjamin Kaduk writes: Hi Christian, Sorry for the very delayed reply (and thanks to Rob for the nudge). On Wed, May 26, 2021 at 06:04:58PM -0400, Christian Hopps wrote: Benjamin Kaduk via Datatracker writes: > Benjamin Kaduk has entered the following ballot position for > draft-ietf-netmod-geo-location-08: Discuss > > When responding, please keep the subject line intact and reply to all > email addresses included in the To and CC lines. (Feel free to cut this > introductory paragraph, however.) > > > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html > for more information about DISCUSS and COMMENT positions. > > > The document, along with other ballot positions, can be found here: > https://datatracker.ietf.org/doc/draft-ietf-netmod-geo-location/ > > > > -- > DISCUSS: > -- > > I think we lack sufficient precision (forgive the pun) in how we talk > about "accuracy" and "precision". Are the leafs that claim to specify > "accuracy" specifying a precision? If so, the precision of a specific > measurement, the precision of the measurements that led to the creation > of the coordinate frame, or something else? Are they doing so in > relative terms (e.g., percentage) or absolute terms (e.g., degrees and > meters)? (There are "units" directives only for "height-accuracy" and > not the others.) How can we we say that we'll have 16 fraction-digits of > precision for lat/long when the maximum accuracy we can say that a > geodetic-system has only gives us 6 fraction-digits for coord-accuracy? > When we say that the "precision of this measurement is indicated by the > reference-frame" is that the same thing as the relevant "-accuracy" > nodes, or something else? Yes, the geodesic-datum is what defines the values and their accuracy. For the precision in the value we choose the fractional digits based on what might be needed, but not to prescribe anything. For decimal degrees e.g., we only need 100s values the rest can be left to the fractional portion. Unfortunately, even your description here still doesn't help me understand what the intended semantics of these values are. To help illustrate my confusion, here are a few possible things that could be what is intended to be conveyed: - the geodetic-datum description of the object has been measured to be within a known delta of the actual object being described, at all points on the object that the coordinate system can describe - the geodetic-datum description of the object is capable of determining relative differences between points on the object to within a particular delta of precision, but those individual coordinate values may be farther than that delta from the actual point on the object that was referred to - the values that are reported in this YANG module reflect measurements that were made and are known to be within some delta of the coordinate system's value that they are reported as - the values that are reported in this YANG module reflect measurements thare are known to be distinguishable from other measurements to within some delta of other measurements relative to that coordinate system, even though the actual position being indicated may diverge from the reported value by more than that delta - the values that are reported in this YANG module reflect measurements that were made and are known to be within some delta of the actual point on the object that the coordinates refer to - the values that are reported in this YANG module reflect measurements that were and are known to be distinguishable from other measurements of points on that object within some delta, but the actual distance from the measured point to the point on the object indicated by the reported coordinates may be larger than that delta In short, there are at least three classes of things at play here: the actual object itself, the coordinate system used to model the object, and values reported in the YANG module (which are assumed to ultimately derive from some form of measurement). To talk about accuracy or precision implies a relationship between elements of two of those classes, and I don't even know which of those classes you're trying to talk about. Let's start with a simple baseline, if you want to dig any deeper than the well understood Lat+Long; do you know what a geodetic datum is? This is required knowledge if you want to get into anything more than the obvious Lat+Long use of this grouping. It defines the coordinates and also the accuracy of measurements. It is out way out of scope for this YANG grouping to try and explain the huge field of geographic locations and geodetic datum and systems. Thanks, Chris. > -- > COMMENT: > ---
Re: [netmod] Benjamin Kaduk's Discuss on draft-ietf-netmod-geo-location-08: (with DISCUSS and COMMENT)
On Sat, Jul 17, 2021 at 02:38:55PM -0400, Christian Hopps wrote: > > Benjamin Kaduk writes: > > > Hi Christian, > > > > Sorry for the very delayed reply (and thanks to Rob for the nudge). > > > > On Wed, May 26, 2021 at 06:04:58PM -0400, Christian Hopps wrote: > >> > >> Benjamin Kaduk via Datatracker writes: > >> > >> > Benjamin Kaduk has entered the following ballot position for > >> > draft-ietf-netmod-geo-location-08: Discuss > >> > > >> > When responding, please keep the subject line intact and reply to all > >> > email addresses included in the To and CC lines. (Feel free to cut this > >> > introductory paragraph, however.) > >> > > >> > > >> > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html > >> > for more information about DISCUSS and COMMENT positions. > >> > > >> > > >> > The document, along with other ballot positions, can be found here: > >> > https://datatracker.ietf.org/doc/draft-ietf-netmod-geo-location/ > >> > > >> > > >> > > >> > -- > >> > DISCUSS: > >> > -- > >> > > >> > I think we lack sufficient precision (forgive the pun) in how we talk > >> > about "accuracy" and "precision". Are the leafs that claim to specify > >> > "accuracy" specifying a precision? If so, the precision of a specific > >> > measurement, the precision of the measurements that led to the creation > >> > of the coordinate frame, or something else? Are they doing so in > >> > relative terms (e.g., percentage) or absolute terms (e.g., degrees and > >> > meters)? (There are "units" directives only for "height-accuracy" and > >> > not the others.) How can we we say that we'll have 16 fraction-digits of > >> > precision for lat/long when the maximum accuracy we can say that a > >> > geodetic-system has only gives us 6 fraction-digits for coord-accuracy? > >> > When we say that the "precision of this measurement is indicated by the > >> > reference-frame" is that the same thing as the relevant "-accuracy" > >> > nodes, or something else? > >> > >> Yes, the geodesic-datum is what defines the values and their accuracy. For > >> the > >> precision in the value we choose the fractional digits based on what might > >> be > >> needed, but not to prescribe anything. For decimal degrees e.g., we only > >> need > >> 100s values the rest can be left to the fractional portion. > > > > Unfortunately, even your description here still doesn't help me understand > > what the intended semantics of these values are. > > > > To help illustrate my confusion, here are a few possible things that could > > be what is intended to be conveyed: > > > > - the geodetic-datum description of the object has been measured to be > > within a known delta of the actual object being described, at all points > > on the object that the coordinate system can describe > > > > - the geodetic-datum description of the object is capable of determining > > relative differences between points on the object to within a particular > > delta of precision, but those individual coordinate values may be farther > > than that delta from the actual point on the object that was referred to > > > > - the values that are reported in this YANG module reflect measurements > > that were made and are known to be within some delta of the coordinate > > system's value that they are reported as > > > > - the values that are reported in this YANG module reflect measurements > > thare are known to be distinguishable from other measurements to within > > some delta of other measurements relative to that coordinate system, even > > though the actual position being indicated may diverge from the reported > > value by more than that delta > > > > - the values that are reported in this YANG module reflect measurements > > that were made and are known to be within some delta of the actual point > > on the object that the coordinates refer to > > > > - the values that are reported in this YANG module reflect measurements > > that were and are known to be distinguishable from other measurements of > > points on that object within some delta, but the actual distance from the > > measured point to the point on the object indicated by the reported > > coordinates may be larger than that delta > > > > In short, there are at least three classes of things at play here: the > > actual object itself, the coordinate system used to model the object, and > > values reported in the YANG module (which are assumed to ultimately derive > > from some form of measurement). To talk about accuracy or precision > > implies a relationship between elements of two of those classes, and I > > don't even know which of those classes you're trying to talk about. > > Let's start with a simple baseline, if you want to dig any deeper than the > well understood Lat+Long; do you know what a geodetic datum is? This is >
Re: [netmod] Benjamin Kaduk's Discuss on draft-ietf-netmod-geo-location-08: (with DISCUSS and COMMENT)
> On Jul 17, 2021, at 6:14 PM, Benjamin Kaduk wrote: > > On Sat, Jul 17, 2021 at 02:38:55PM -0400, Christian Hopps wrote: >> >> Benjamin Kaduk writes: >> >>> Hi Christian, >>> >>> Sorry for the very delayed reply (and thanks to Rob for the nudge). >>> >>> On Wed, May 26, 2021 at 06:04:58PM -0400, Christian Hopps wrote: Benjamin Kaduk via Datatracker writes: > Benjamin Kaduk has entered the following ballot position for > draft-ietf-netmod-geo-location-08: Discuss > > When responding, please keep the subject line intact and reply to all > email addresses included in the To and CC lines. (Feel free to cut this > introductory paragraph, however.) > > > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html > for more information about DISCUSS and COMMENT positions. > > > The document, along with other ballot positions, can be found here: > https://datatracker.ietf.org/doc/draft-ietf-netmod-geo-location/ > > > > -- > DISCUSS: > -- > > I think we lack sufficient precision (forgive the pun) in how we talk > about "accuracy" and "precision". Are the leafs that claim to specify > "accuracy" specifying a precision? If so, the precision of a specific > measurement, the precision of the measurements that led to the creation > of the coordinate frame, or something else? Are they doing so in > relative terms (e.g., percentage) or absolute terms (e.g., degrees and > meters)? (There are "units" directives only for "height-accuracy" and > not the others.) How can we we say that we'll have 16 fraction-digits of > precision for lat/long when the maximum accuracy we can say that a > geodetic-system has only gives us 6 fraction-digits for coord-accuracy? > When we say that the "precision of this measurement is indicated by the > reference-frame" is that the same thing as the relevant "-accuracy" > nodes, or something else? Yes, the geodesic-datum is what defines the values and their accuracy. For the precision in the value we choose the fractional digits based on what might be needed, but not to prescribe anything. For decimal degrees e.g., we only need 100s values the rest can be left to the fractional portion. >>> >>> Unfortunately, even your description here still doesn't help me understand >>> what the intended semantics of these values are. >>> >>> To help illustrate my confusion, here are a few possible things that could >>> be what is intended to be conveyed: >>> >>> - the geodetic-datum description of the object has been measured to be >>> within a known delta of the actual object being described, at all points >>> on the object that the coordinate system can describe >>> >>> - the geodetic-datum description of the object is capable of determining >>> relative differences between points on the object to within a particular >>> delta of precision, but those individual coordinate values may be farther >>> than that delta from the actual point on the object that was referred to >>> >>> - the values that are reported in this YANG module reflect measurements >>> that were made and are known to be within some delta of the coordinate >>> system's value that they are reported as >>> >>> - the values that are reported in this YANG module reflect measurements >>> thare are known to be distinguishable from other measurements to within >>> some delta of other measurements relative to that coordinate system, even >>> though the actual position being indicated may diverge from the reported >>> value by more than that delta >>> >>> - the values that are reported in this YANG module reflect measurements >>> that were made and are known to be within some delta of the actual point >>> on the object that the coordinates refer to >>> >>> - the values that are reported in this YANG module reflect measurements >>> that were and are known to be distinguishable from other measurements of >>> points on that object within some delta, but the actual distance from the >>> measured point to the point on the object indicated by the reported >>> coordinates may be larger than that delta >>> >>> In short, there are at least three classes of things at play here: the >>> actual object itself, the coordinate system used to model the object, and >>> values reported in the YANG module (which are assumed to ultimately derive >>> from some form of measurement). To talk about accuracy or precision >>> implies a relationship between elements of two of those classes, and I >>> don't even know which of those classes you're trying to talk about. >> >> Let's start with a simple baseline, if you want to dig any deeper than the >> well understood Lat+Long; do you kno
Re: [netmod] Benjamin Kaduk's Discuss on draft-ietf-netmod-geo-location-08: (with DISCUSS and COMMENT)
On Sat, Jul 17, 2021 at 07:17:09PM -0400, Christian Hopps wrote: > > > > On Jul 17, 2021, at 6:14 PM, Benjamin Kaduk 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? And, if the concept here is that "I made a measurement, and my measurement device reported a value to 1/10 of a decimal degree", that would typically correspond to a "precision" rather than an "accuracy" (https://en.wikipedia.org/wiki/Accuracy_and_precision). In either case, I think that "accuracy of the measurement recorded in the grouping" is a qualitatively different concept of "accuracy" than the listed accuracy of the geodetic-datum, which (AIUI) relates to the maximum deviation between the model of the object used by the coordinate system and the actual physical object. So it's not really clear that we should be talking the one "overriding" the other. -Ben ___ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod
