RE: [Geopriv] Religious Terminology Discussions

From: Roger Marshall ^lt;>
Date: Tue Nov 27 2007 - 17:32:56 EST

Thanks for your reply. It seems that we're left with the following 3 options then:
i. adopt the direct position term in lieu of all other terms which relate to a coordinate pair, etc.
ii. continue to use whatever term we like - outside of OGC/ISO GIS stds.,
iii. wait until the OGC comes up with some new std. terms - then evaluate.
I think we'll end up doing the second, and likely, the third - though too late to do anything about published RFCs.
-roger marshall.


        From: Carl Reed OGC Account []
        Sent: Tuesday, November 27, 2007 1:42 PM
        To: Roger Marshall; Hannes Tschofenig; James M. Polk
        Cc:; Marc Linsner
        Subject: Re: [Geopriv] Religious Terminology Discussions
        Roger -
        *Warning* - a bit lengthy.
        Appears that you have put your finger on one of the long standing issues in the traditional GIS community! For decades, every vendor, every research project, every standards organization seems to have wanted to put their own imprint on the discipline by defining a new term instead of using a term that had been previously defined. Causes a bit of a semantic issue, doesn't it! And your list while well researched is not complete. There are other terms in use also. In the OGC, we have been able to "pin down" and agree on a number of terms and phrases, such as coordinate, coordinate pair, coordinate system, and coordinate reference system. For example, the following are from 19107 and used in all OGC and ISO standards related to geo content:
        one of a sequence of numbers designating the position of a point in N-dimensional space
        NOTE In a coordinate reference system, the numbers must be qualified by units.
        coordinate dimension
        number of measurements or axes needed to describe a position in a coordinate system
        coordinate reference system
        coordinate system that is related to the real world by a datum
        [ISO 19111]
        coordinate system
        set of (mathematical) rules for specifying how coordinates are to be assigned to points
        Notice that none of these definitions refer to lat/long or a geodetic point etc. Point is handled as follows:
        0-dimensional geometric primitive, representing a position
        NOTE The boundary of a point is the empty set.
        So we still need another definition:
        direct position
        position described by a single set of coordinates within a coordinate reference system
        So, Roger, you are correct. Direct position AKA position is the best overall generic term. However, please remember that this is a generic term with regard to location in space - not just on the earth. This is why there is no reference to geo this and geo that. As a matter of fact, there are many different coordinate systems - not just a geodetic coordinate systems. There are local coordinate systems, dynamic coordinate systems, linear coordinate systems, polar coordinate systems. Hence the generality (or abstraction) of the definition for "direct position" used in ISO and the OGC. FYI, the OGC members have formed an ad-hoc group to develop a general model for all coordinate systems that could be used in the geo space.
        I agree, as you point out, that it sure would be nice to have a self describing term we could all use to describe a position on the surface (or above/below) of the earth.
        The final piece of the puzzle is to be found in 19111 - Spatial Referencing by coordinates. In that document, we find:
        geodetic latitude
        ellipsoidal latitude
        angle from the equatorial plane to the perpendicular to the ellipsoid through a given point, northwards treated as positive
        geodetic longitude
        ellipsoidal longitude
        angle from the prime meridian plane to the meridian plane of a given point, eastward treated as positive
        Now a bit of a kicker. When dealing with lat/long such as in WGS 84, the terminology used is "geographic coordinates". and "geographic coordinate reference system" or for short "geographics". In terms of other CRS, as a geometric process, in general a map projection is a set of formulae that converts geodetic latitude and longitude to plane (map) coordinates AKA planar coordinates.
        If you wish, you can download 19111 for free from the OGC web site . This document was written by a group of geodists and mathematicians so it can be a bit heavy going at times - but it is an excellent piece of work.
        Sorry for the length posting, put as we know there is nothing simple about working with an ellipsoidal earth on flat paper - or in computers :-)


        ----- Original Message -----
        From: "Roger Marshall" <>
        To: "Carl Reed OGC Account" <>; "Hannes Tschofenig" <>; "James M. Polk" <>
        Cc: <>; "Marc Linsner" <>
        Sent: Tuesday, November 27, 2007 12:41 PM
        Subject: RE: [Geopriv] Religious Terminology Discussions
> Hi Carl,
> Which term(s), according to this or other GIS related sources, relate
> solely to a lat/lon coordinate pair, as in a specific 2-D grid-based
> position? It isn't clear to me, so I've made the following
> observations/assumptions in an effort to get a common set of terms.
> I scanned the ISOTC 211 ( glossary, but found
> terms which only came close, such as:
> geodetic latitude
> geodetic longitude
> geographic data
> coordinate set
> coordinate tuple
> data
> data element
> dataset
> direct position*
> point
> position
> spacial reference
> All these are ok, yet there are many terms not found in the ISO/TC 211
> glossary, but which have been popularized in industry and within some
> IETF drafts, and that have been used more-or-less interchangeably. For
> the 2-D case, these include (non-exhaustive):
> geographic location
> geographic position
> geoposition
> geodetic location
> geodetic position
> geo location
> geo position
> geo
> coordinate pair
> coordinate location
> coordinate position
> lat/lon coordinates
> lat/lon pair
> lat/lon
> x,y
> ...
> Assuming all of the terms in this second list are trying to get at the
> same thing (which I don't necessarily agree should be the case), when
> comparing to the ISO/TC 211 terms, it seemed to me that the term,
> 'direct position', fit's best (it's possible I missed spotting a better
> one).
> The definition for 'direct position' seems adequate:
> "position described by a single set of coordinates within a coordinate
> reference system"
> ...but the term itself falls short as being self-described when compared
> to potential alternatives, such as: "geographic position" or "coordinate
> position", either of which I would prefer when representing the
> definition for 'direct position'.
> -roger marshall.
>> -----Original Message-----
>> From: Carl Reed OGC Account []
>> Sent: Monday, November 26, 2007 5:38 PM
>> To: Hannes Tschofenig; James M. Polk
>> Cc:; Marc Linsner
>> Subject: Re: [Geopriv] Religious Terminology Discussions
>> If it makes everyone feel any better - this from the Image
>> Geopositioning Service Interface standards working group in the OGC:
>> Relative to item 1) in my message copied below, I scanned the
>> ASPRS Manual of Photogrammetry fifth edition (2004) for the
>> terms georeferencing, geopositioning, and geolocation or
>> similar. As I said, this manual does not include a
>> dictionary of terms or even formal definitions of any terms.
>> I found the terms georeferencing and geopositioning used in
>> different sections, with unclear meanings. I also found
>> several sections where one of these terms would have fit, but
>> was not used. I did not find any uses of the term
>> geolocation or similar.
>> I conclude that this Manual of Photogrammetry does not
>> provide any information that would help the IGS RWG in
>> deciding what terms to use.
>> Arliss
>> FYI: Image geopositioning is about the ability to control
>> image rectification from real time imagery collection
>> systems, such as when digital imagery is being provided as a
>> data stream from an Unmanned Aerial Vehicle (UAV).
>> Having said the above, ISO TC 211 does maintain a fairly
>> extensive terminology database of terms used in the
>> geospatial community.
>> Cheers
>> Carl
>> ----- Original Message -----
>> From: "Hannes Tschofenig" <>
>> To: "James M. Polk" <>
>> Cc: <>; "Marc Linsner" <>
>> Sent: Monday, November 26, 2007 2:07 PM
>> Subject: [Geopriv] Religious Terminology Discussions
>> > Hi all,
>> >
>> > we had many terminology discussions in this group about conveyance,
>> > location retrieval, Using Protocols, etc.
>> >
>> > All these discussions lead to absolutely NOTHING. We did not learn
>> > anything new. It was just a complete waste of time. We
>> aren't even left
>> > with good terminology*.
>> >
>> > Maybe it is time to throw some of the old (and not so well
>> defined) terms
>> > aboard and develop better onces (if someone has the
>> energy). Btw, Richard
>> > has already taken the first step to re-work the terminology and the
>> > architecture, see
>> >
>> >
>> > Ciao
>> > Hannes
>> >
>> > (*): Together with Henning we tried to write a tutorial
>> about GEOPRIV and
>> > we noticed that the GEOPRIV requirements RFC (that outlines also
>> > architectural parts) is very much outdated and does not
>> help to present a
>> > solid story.
>> >
>> >
>> >
>> >
>> > James M. Polk wrote:
>> >> At 04:42 PM 11/21/2007, Hannes Tschofenig wrote:
>> >>> Tomorrow I will send you a message flow how a SIP proxy requests
>> >>> location information and a URI for usage with SIP
>> Location Conveyance.
>> >>
>> >> Location Conveyance does not define how any entity
>> retrieves location -
>> >> so this flow should be interesting.
>> >>
>> >> BTW - I don't consider a dereference "location retrieval", that's
>> >> conveyance.
>> >>
>> >>> I am already too tired today.
>> >>>
>> >>> Ciao
>> >>> Hannes
>> >>>
>> >>>
>> >>>
>> >>>
>> >>> Marc Linsner wrote:
>> >>>>
>> >>>> Hannes,
>> >>>>
>> >>>>
>> >>>>> I am interested in the case where the SIP obtains
>> location information
>> >>>>> and/or a LbyR from the LIS. I believe that the two
>> entities, namely
>> >>>>> the SIP proxy and the LIS, will not be co-located in realistic
>> >>>>> deployments. A simple protocol is needed. The HELD
>> identity extension
>> >>>>> document provides this functionality.
>> >>>>>
>> >>>>>
>> >>>>
>> >>>> How?
>> >>>>
>> >>>> -Marc-
>> >>>>
>> >>>
>> >>>
>> >>>
>> >>> _______________________________________________
>> >>> Geopriv mailing list
>> >>>
>> >>>
>> >
>> >
>> >
>> > _______________________________________________
>> > Geopriv mailing list
>> >
>> >
>> _______________________________________________
>> Geopriv mailing list
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Received on Tue, 27 Nov 2007 14:32:56 -0800

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