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  • Dan Foster
    Hello, Let s start a list of point-specific concepts that might be useful to share between GPS or mapping applications. I think having such a list will be
    Message 1 of 14 , Oct 18, 2001
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      Hello,

      Let's start a list of point-specific concepts that might be useful to
      share between GPS or mapping applications. I think having such a list
      will be helpful when we discuss what tags and elements to include in
      the XML spec.

      GPS Waypoint:
      a <point> that's intended to be sent to a GPS and used as a navigation
      aide.

      GPS Trackpoint:
      a <point> marking a position along a path.

      Map Annotation:
      a <point> on a map with some formatted text or a symbol.

      Map Calibration Point:
      a <point> on a map that ties a lat/lon <point> to an x/y pixel
      location.

      Destination:
      a <point> to which you are navigating.

      Others?


      --
      Dan Foster
      TopoGrafix - GPS Software, Waypoints, and Maps
      http://www.topografix.com - mailto:egroups@...
    • Alan Morris G4ENS
      jfmezei@videotron.ca wrote:- ... This is a subject that I have been giving much thought to for some time now. I have a few years of collected waypoints from
      Message 2 of 14 , Oct 18, 2001
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        jfmezei@... wrote:-

        > Since each of these have their own precision (or lack thereof), if someone is to rely on that list I provide, it would be nice for them to be able to know which waypoints might be more precice (taken by GPS) and which might be off by some distance (MAN200R).

        > Not sure there would be a need to defide the contents of that field. One could expect each provider of XML data sets to provide a description of that "source" field if it is to be used.

        > comments ?

        This is a subject that I have been giving much thought to for some time now. I have a few years of collected waypoints from various sources and the precision of the posit cannot be recorded in existing file formats that I have seen.

        Three methods come to mind.

        1. A field with the possible error in miles, Km or metres - disadvantages: needs to be worked-out & takes up more space. Useful for items such as campsite posits taken from printed guides that often are a mile or more in error of an actual GPS fix.

        2. A single byte indicator. This could be added to any posit at the end, just like a programming variable. $,#,!,% etc. No indicator would indicate unknown precision. Different characters could also indicate a different source for the data, with a key table earlier in the file, so #2 could indicate a different source to #49.

        3. Reduce the number of significant digits from the right. The receiving software would need to take this into account. This is the method used by radio hams when transmitting their posit, which is displayed in real time on maps. Allows any required lack of precision. ie for privacy.

        This method could also be used with the time field.

        > 20001108T093014Z.120 (Nov 08, 2000 at 9:30:14.120 GMT)

        allowing 200011 to indicate the month of Nov 2000.
        --
        Alan R Morris, G4ENS.
        Bury St Edmunds, Suffolk, UK.
        No HTML, using a Psion 5mx & Nokia 6210e at 9.6Kb.
      • davewissenbach@yahoo.com
        ... to ... list ... I don t think that destination is a type of point. I think that origin and destination are required elements contained in every path or
        Message 3 of 14 , Oct 19, 2001
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          --- In gpsxml@y..., Dan Foster <egroups@t...> wrote:
          > Hello,
          >
          > Let's start a list of point-specific concepts that might be useful
          to
          > share between GPS or mapping applications. I think having such a
          list
          > will be helpful when we discuss what tags and elements to include in
          > the XML spec.
          >
          > GPS Waypoint:
          >
          > GPS Trackpoint:

          > Map Annotation:

          > Map Calibration Point:

          > Destination:

          I don't think that destination is a type of point. I think that
          origin and destination are required elements contained in every path
          or sub-path. The origin and destination should be named points, which
          means to me what the wpt/id attribute is required for origin and
          destination.

          > Others?
          >
          >
          > --
          > Dan Foster
          > TopoGrafix - GPS Software, Waypoints, and Maps
          > http://www.topografix.com - mailto:egroups@t...
        • Alan Morris G4ENS
          Henry C. Schmitt wrote:- ... Maidenhead is not a datum, it is a special format for displaying Lat/Long in one short code. It is used by
          Message 4 of 14 , Oct 19, 2001
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            "Henry C. Schmitt" <Henry@...> wrote:-

            > <grid datum="maidenhead">FN00ak</grid>

            Maidenhead is not a datum, it is a special format for displaying Lat/Long in one short code. It is used by radio hams and replaced an earlier system known as 'QRA' locator, (I was at ZL08d) which only covered Europe. Whereas Maidenhead is world wide.

            The format was finalised in the UK town of Maidenhead, hence it's name, and at that time the use of a datum was never concidered (or even known about). Today, WGS84 is the accepted datum for Maidenhead.
            --
            Alan R Morris, G4ENS.
            Bury St Edmunds, Suffolk, UK.
            No HTML, using a Psion 5mx & Nokia 6210e at 9.6Kb.
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