PDOP or GDOP

Discussion in 'Global Navigation Satellite Systems' started by Johnson, May 13, 2009.

  1. Johnson

    Johnson Guest

    I would like to know in general which one is typically chosen to
    indicate the quality of DOP and GPS accuracy, PDOP or GDOP?
     
    Johnson, May 13, 2009
    #1
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  2. Johnson

    Sam Wormley Guest

    Johnson wrote:
    > I would like to know in general which one is typically chosen to
    > indicate the quality of DOP and GPS accuracy, PDOP or GDOP?


    http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html


    PDOP = Position Dilution of Precision (3-D), sometimes the Spherical DOP.
    HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    VDOP = Vertical Dilution of Precision (Height).
    TDOP = Time Dilution of Precision (Time).

    I use PDOP and HDOP
     
    Sam Wormley, May 13, 2009
    #2
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  3. "Sam Wormley" <> wrote in message
    news:qWFOl.697079$yE1.166398@attbi_s21...
    > Johnson wrote:
    >> I would like to know in general which one is typically chosen to indicate
    >> the quality of DOP and GPS accuracy, PDOP or GDOP?

    >
    > http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html
    >
    >
    > PDOP = Position Dilution of Precision (3-D), sometimes the Spherical DOP.
    > HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    > VDOP = Vertical Dilution of Precision (Height).
    > TDOP = Time Dilution of Precision (Time).
    >
    > I use PDOP and HDOP


    Amd it is probably worth mentioning the GDOP is a term that refers to all of
    these--they are all geometry only estimates of relative precison.. So the
    choice is never between PDOP and GDOP ) as in the orignal post question) as
    PDOP is "one of the kinds of GDOP". (The webpage calls the above
    "components" of GDOP but they are not components in the usual sense.)
     
    David L. Wilson, May 14, 2009
    #3
  4. Johnson

    Guest

    On Wed, 13 May 2009 23:23:04 GMT, "David L. Wilson"
    <> wrote:

    >
    >"Sam Wormley" <> wrote in message
    >news:qWFOl.697079$yE1.166398@attbi_s21...
    >> Johnson wrote:
    >>> I would like to know in general which one is typically chosen to indicate
    >>> the quality of DOP and GPS accuracy, PDOP or GDOP?

    >>
    >> http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html
    >>
    >>
    >> PDOP = Position Dilution of Precision (3-D), sometimes the Spherical DOP.
    >> HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    >> VDOP = Vertical Dilution of Precision (Height).
    >> TDOP = Time Dilution of Precision (Time).
    >>
    >> I use PDOP and HDOP

    >
    >Amd it is probably worth mentioning the GDOP is a term that refers to all of
    >these--they are all geometry only estimates of relative precison.. So the
    >choice is never between PDOP and GDOP ) as in the orignal post question) as
    >PDOP is "one of the kinds of GDOP". (The webpage calls the above
    >"components" of GDOP but they are not components in the usual sense.)
    >

    Avoid NOJOP = Dilution of the economy (Money).
     
    , May 14, 2009
    #4
  5. Johnson

    T Driver Guest

    On May 13, 5:23 pm, "David L. Wilson" <> wrote:
    > "Sam Wormley" <> wrote in message
    >
    > news:qWFOl.697079$yE1.166398@attbi_s21...
    >
    > > Johnson wrote:
    > >> I would like to know in general which one is typically chosen to indicate
    > >> the quality of DOP and GPS accuracy, PDOP or GDOP?

    >
    > >  http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html

    >
    > > PDOP = Position Dilution of Precision (3-D), sometimes the Spherical DOP.
    > > HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    > > VDOP = Vertical Dilution of Precision (Height).
    > > TDOP = Time Dilution of Precision (Time).

    >
    > >   I use PDOP and HDOP

    >
    > Amd it is probably worth mentioning the GDOP is a term that refers to allof
    > these--they are all geometry only estimates of relative precison..  So the
    > choice is never between PDOP and GDOP ) as in the orignal post question) as
    > PDOP is "one of the kinds of GDOP".  (The webpage calls the above
    > "components" of GDOP but they are not components in the usual sense.)


    You can think of DOP along each coordinate axis, so that in a North-
    East-Down reference frame there is a North DOP, an East DOP as well as
    the vertical DOP.
    HDOP = sqrt( northDop^2 + eastDOP^2)
    PDOP = sqrt(HDOP^2 + VDOP^2)
    Finally, GDOP = sqrt(PDOP^2 + TDOP^2)
    So, use PDOP if you are interested in your receiver's position
    dilution of precision, use GDOP if you are interested in accounting
    for the Time dilution of precision as well. In my experience, most
    people use PDOP or TDOP, but rarely GDOP.
     
    T Driver, May 14, 2009
    #5
  6. Johnson

    Guest

    On May 13, 9:11 pm, Johnson <> wrote:
    > I would like to know in general which one is typically chosen to
    > indicate the quality of DOP and GPS accuracy, PDOP or GDOP?


    You also need to be aware that it is possible to have a GPS unit
    report a good DOP figure, small error ellipse values and still be some
    10-20 km in error on its position. I have seen this with units
    positioned around 50 deg N and 45 deg S where the sky view is severely
    limited. In one case the receiver was on a windowsill in a tall
    building with other buildings across the street. It just worked out
    that with the signal reflections and satellite obscuration present,
    the location algorithms got a 'good' solution for the position that
    just happened to be wrong.

    DOP != GPS position accuracy.
     
    , May 14, 2009
    #6
  7. Johnson

    Sam Wormley Guest

    wrote:
    > On May 13, 9:11 pm, Johnson <> wrote:
    >> I would like to know in general which one is typically chosen to
    >> indicate the quality of DOP and GPS accuracy, PDOP or GDOP?

    >
    > You also need to be aware that it is possible to have a GPS unit
    > report a good DOP figure, small error ellipse values and still be some
    > 10-20 km in error on its position. I have seen this with units
    > positioned around 50 deg N and 45 deg S where the sky view is severely
    > limited. In one case the receiver was on a windowsill in a tall
    > building with other buildings across the street. It just worked out
    > that with the signal reflections and satellite obscuration present,
    > the location algorithms got a 'good' solution for the position that
    > just happened to be wrong.
    >
    > DOP != GPS position accuracy.



    Estimated Position Error (EPE) and Error Sources

    EPE (1-sigma) = HDOP * UERE (1-sigma) (1)

    Multiplying the HDOP * UERE * 2 gives EPE (2drms) and is commonly taken as the 95% limit
    for the magnitude of the horizontal error. The probability of horizontal error is within
    an ellipse of radius 2drms ranges between 0.95 and 0.98 depending on the ratio of the
    ellipse semi-axes. User Equivalent Range Error (UERE) is computed in the tables lower on
    this page.

    EPE (2drms) = 2 * HDOP * SQRT [URE^2 + UEE^2] (2)

    HDOP (Horizontal Geometric Dilution of Precision), GDOP, PDOP and VDOP are determined by
    the geometry of the current satellites visible above the receiver's mask angle with
    respect to user receiver's antenna. DOPs can be degraded (made larger) by signal
    obstruction due to terrain, foliage, building, vehicle structure, etc.

    URE (User Range Error) is an estimate of "Signals in Space" errors, i.e., ephemeris data,
    satellite clocks, ionospheric delay and tropospheric delay. These errors can be greatly
    reduced by differential and multiple frequency techniques. Differential correction sources
    include user provided reference stations, community base stations, governmental beacon
    transmissions, FM sub-carrier transmissions and geosynchronous satellite transmissions.

    UEE (User Equipment Errors) includes receiver noise, multipath, antenna orientation,
    EMI/RFI. Receiver and antenna design can greatly reduce UEE error sources--usually at
    substantial cost.

    Position error can range from tens of meters (recreational) to a few millimeters (survey)
    depending on equipment, signals and usage. Professional mapping and survey equipment often
    includes user-settable minimum thresholds for SNR, mask angle, DOP, number of SVs used, etc.
     
    Sam Wormley, May 14, 2009
    #7
  8. Johnson

    Guest

    On May 14, 4:22 pm, Sam Wormley <> wrote:
    > wrote:
    > > On May 13, 9:11 pm, Johnson <> wrote:
    > >> I would like to know in general which one is typically chosen to
    > >> indicate the quality of DOP and GPS accuracy, PDOP or GDOP?

    >
    > > You also need to be aware that it is possible to have a GPS unit
    > > report a good DOP figure, small error ellipse values and still be some
    > > 10-20 km in error on its position.  I have seen this with units
    > > positioned around 50 deg N and 45 deg S where the sky view is severely
    > > limited.  In one case the receiver was on a windowsill in a tall
    > > building with other buildings across the street.  It just worked out
    > > that with the signal reflections and satellite obscuration present,
    > > the location algorithms got a 'good' solution for the position that
    > > just happened to be wrong.

    >
    > > DOP != GPS position accuracy.

    >
    > Estimated Position Error (EPE) and Error Sources
    >
    >            EPE (1-sigma) = HDOP * UERE (1-sigma)               (1)
    >
    > Multiplying the HDOP * UERE * 2 gives EPE (2drms) and is commonly taken as the 95% limit
    > for the magnitude of the horizontal error. The probability of horizontal error is within
    > an ellipse of radius 2drms ranges between 0.95 and 0.98 depending on the ratio of the
    > ellipse semi-axes. User Equivalent Range Error (UERE) is computed in the tables lower on
    > this page.
    >
    >            EPE (2drms) = 2 * HDOP * SQRT [URE^2 + UEE^2]       (2)
    >
    > HDOP (Horizontal Geometric Dilution of Precision), GDOP, PDOP and VDOP are determined by
    > the geometry of the current satellites visible above the receiver's mask angle with
    > respect to user receiver's antenna. DOPs can be degraded (made larger) bysignal
    > obstruction due to terrain, foliage, building, vehicle structure, etc.
    >
    > URE (User Range Error) is an estimate of "Signals in Space" errors, i.e.,ephemeris data,
    > satellite clocks, ionospheric delay and tropospheric delay. These errors can be greatly
    > reduced by differential and multiple frequency techniques. Differential correction sources
    > include user provided reference stations, community base stations, governmental beacon
    > transmissions, FM sub-carrier transmissions and geosynchronous satellite transmissions.
    >
    > UEE (User Equipment Errors) includes receiver noise, multipath, antenna orientation,
    > EMI/RFI. Receiver and antenna design can greatly reduce UEE error sources--usually at
    > substantial cost.
    >
    > Position error can range from tens of meters (recreational) to a few millimeters (survey)
    > depending on equipment, signals and usage. Professional mapping and survey equipment often
    > includes user-settable minimum thresholds for SNR, mask angle, DOP, number of SVs used, etc.


    In the cases that I was alluding to (IIRC) the reported position error
    estimate from the GPS (I would rather not identify the brand as this
    is irrelevant, save that it was from one of the industry major
    players) was less than 10 metres and the DOP value was well within the
    normal range for a good fix so it was not possible to declare the fix
    invalid on either of these grounds. The reported position was stable
    for a considerable period but between 10 and 20 km in error when
    compared to the true position.

    Ian
     
    , May 14, 2009
    #8
  9. "T Driver" <> wrote in message
    news:...
    On May 13, 5:23 pm, "David L. Wilson" <> wrote:
    > "Sam Wormley" <> wrote in message
    >
    > news:qWFOl.697079$yE1.166398@attbi_s21...
    >
    > > Johnson wrote:
    > >> I would like to know in general which one is typically chosen to
    > >> indicate
    > >> the quality of DOP and GPS accuracy, PDOP or GDOP?

    >
    > > http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html

    >
    > > PDOP = Position Dilution of Precision (3-D), sometimes the Spherical
    > > DOP.
    > > HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    > > VDOP = Vertical Dilution of Precision (Height).
    > > TDOP = Time Dilution of Precision (Time).

    >
    > > I use PDOP and HDOP

    >
    > Amd it is probably worth mentioning the GDOP is a term that refers to all
    > of
    > these--they are all geometry only estimates of relative precison.. So the
    > choice is never between PDOP and GDOP ) as in the orignal post question)
    > as
    > PDOP is "one of the kinds of GDOP". (The webpage calls the above
    > "components" of GDOP but they are not components in the usual sense.)


    You can think of DOP along each coordinate axis, so that in a North-
    East-Down reference frame there is a North DOP, an East DOP as well as
    the vertical DOP.
    HDOP = sqrt( northDop^2 + eastDOP^2)
    PDOP = sqrt(HDOP^2 + VDOP^2)
    Finally, GDOP = sqrt(PDOP^2 + TDOP^2)

    I have not seen the last equation and it has a problem in that exactly in
    what units of what measurement is it a Dilution of Precision? Most people
    use GDOP as a general term for geometric dilution of precision of which the
    other DOP's are types of.
     
    David L. Wilson, May 14, 2009
    #9
  10. Johnson

    T Driver Guest

    On May 14, 4:13 pm, "David L. Wilson" <> wrote:
    > "T Driver" <> wrote in message
    >
    > news:...
    > On May 13, 5:23 pm, "David L. Wilson" <> wrote:
    >
    >
    >
    > > "Sam Wormley" <> wrote in message

    >
    > >news:qWFOl.697079$yE1.166398@attbi_s21...

    >
    > > > Johnson wrote:
    > > >> I would like to know in general which one is typically chosen to
    > > >> indicate
    > > >> the quality of DOP and GPS accuracy, PDOP or GDOP?

    >
    > > >http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html

    >
    > > > PDOP = Position Dilution of Precision (3-D), sometimes the Spherical
    > > > DOP.
    > > > HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    > > > VDOP = Vertical Dilution of Precision (Height).
    > > > TDOP = Time Dilution of Precision (Time).

    >
    > > > I use PDOP and HDOP

    >
    > > Amd it is probably worth mentioning the GDOP is a term that refers to all
    > > of
    > > these--they are all geometry only estimates of relative precison.. So the
    > > choice is never between PDOP and GDOP ) as in the orignal post question)
    > > as
    > > PDOP is "one of the kinds of GDOP". (The webpage calls the above
    > > "components" of GDOP but they are not components in the usual sense.)

    >
    > You can think of DOP along each coordinate axis, so that in a North-
    > East-Down reference frame there is a North DOP, an East DOP as well as
    > the vertical DOP.
    > HDOP = sqrt( northDop^2 + eastDOP^2)
    > PDOP = sqrt(HDOP^2 + VDOP^2)
    > Finally, GDOP = sqrt(PDOP^2 + TDOP^2)
    >
    > I have not seen the last equation and it has a problem in that exactly in
    > what units of what measurement is it a Dilution of Precision?  Most people
    > use GDOP as a general term for geometric dilution of precision of which the
    > other DOP's are types of.


    DOP has no units. This confuses people sometimes, as you can become
    accustomed to associating DOP with your navigation accuracy 1-for-1.
    With that assumption, some might think DOP would have the units of
    meters. Navigation accuracy actually takes into account the
    pseudorange errors as well, which is where the length units come in.
    See the Position Errors section here: http://blogs.agi.com/navigationAccuracy/?page_id=6
    Ted
     
    T Driver, May 15, 2009
    #10
  11. Johnson

    Johnson Guest

    David L. Wilson wrote:
    > "T Driver" <> wrote in message
    > news:...
    > On May 13, 5:23 pm, "David L. Wilson" <> wrote:
    >> "Sam Wormley" <> wrote in message
    >>
    >> news:qWFOl.697079$yE1.166398@attbi_s21...
    >>
    >>> Johnson wrote:
    >>>> I would like to know in general which one is typically chosen to
    >>>> indicate
    >>>> the quality of DOP and GPS accuracy, PDOP or GDOP?
    >>> http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html
    >>> PDOP = Position Dilution of Precision (3-D), sometimes the Spherical
    >>> DOP.
    >>> HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    >>> VDOP = Vertical Dilution of Precision (Height).
    >>> TDOP = Time Dilution of Precision (Time).
    >>> I use PDOP and HDOP

    >> Amd it is probably worth mentioning the GDOP is a term that refers to all
    >> of
    >> these--they are all geometry only estimates of relative precison.. So the
    >> choice is never between PDOP and GDOP ) as in the orignal post question)
    >> as
    >> PDOP is "one of the kinds of GDOP". (The webpage calls the above
    >> "components" of GDOP but they are not components in the usual sense.)

    >
    > You can think of DOP along each coordinate axis, so that in a North-
    > East-Down reference frame there is a North DOP, an East DOP as well as
    > the vertical DOP.
    > HDOP = sqrt( northDop^2 + eastDOP^2)
    > PDOP = sqrt(HDOP^2 + VDOP^2)
    > Finally, GDOP = sqrt(PDOP^2 + TDOP^2)
    >
    > I have not seen the last equation and it has a problem in that exactly in
    > what units of what measurement is it a Dilution of Precision? Most people
    > use GDOP as a general term for geometric dilution of precision of which the
    > other DOP's are types of.
    >
    >

    "Most people use GDOP as a general term for geometric dilution of
    precision of which the other DOP's are types of. " I am actually looking
    for DOP so I think GDOP will be my choice.

    Thanks for all your replies.
     
    Johnson, May 15, 2009
    #11

  12. >"T Driver" <> wrote in message
    >news:...

    On May 14, 4:13 pm, "David L. Wilson" <> wrote:
    >> "T Driver" <> wrote in message
    >>
    >> news:...
    >> On May 13, 5:23 pm, "David L. Wilson" <> wrote:
    >>
    >>
    >>
    >> > "Sam Wormley" <> wrote in message

    >>
    >> >news:qWFOl.697079$yE1.166398@attbi_s21...

    >>
    >> > > Johnson wrote:
    >> > >> I would like to know in general which one is typically chosen to
    >> > >> indicate
    >> > >> the quality of DOP and GPS accuracy, PDOP or GDOP?

    >>
    >> > >http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html

    >>
    >> > > PDOP = Position Dilution of Precision (3-D), sometimes the Spherical
    >> > > DOP.
    >> > > HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    >> > > VDOP = Vertical Dilution of Precision (Height).
    >> > > TDOP = Time Dilution of Precision (Time).

    >>
    >> > > I use PDOP and HDOP

    >>
    >> > Amd it is probably worth mentioning the GDOP is a term that refers to
    >> > all
    >> > of
    >> > these--they are all geometry only estimates of relative precison.. So
    >> > the
    >> > choice is never between PDOP and GDOP ) as in the orignal post
    >> > question)
    >> > as
    >> > PDOP is "one of the kinds of GDOP". (The webpage calls the above
    >> > "components" of GDOP but they are not components in the usual sense.)

    >
    >>> You can think of DOP along each coordinate axis, so that in a North-

    >> East-Down reference frame there is a North DOP, an East DOP as well as
    >> the vertical DOP.
    >> HDOP = sqrt( northDop^2 + eastDOP^2)
    >> PDOP = sqrt(HDOP^2 + VDOP^2)
    >> Finally, GDOP = sqrt(PDOP^2 + TDOP^2)
    >>
    >> I have not seen the last equation and it has a problem in that exactly in
    >> what units of what measurement is it a Dilution of Precision? Most people
    >> use GDOP as a general term for geometric dilution of precision of which
    >> the
    >> other DOP's are types of.


    >DOP has no units. This confuses people sometimes, as you can become
    >accustomed to associating DOP with your navigation accuracy 1-for-1.
    >With that assumption, some might think DOP would have the units of
    >meters. Navigation accuracy actually takes into account the
    >pseudorange errors as well, which is where the length units come in.
    >See the Position Errors section here:
    >http://blogs.agi.com/navigationAccuracy/?page_id=6
    >Ted


    No confusion here. Understood it has not units but it is meant to be a
    dilution of precision due to satellite geometry and only so on a statistical
    basis. GDOP is the general term for HDOP, PDOP, and TDOP but to consider
    GDOP as a RMS of PDOP and TDOP yeilds a really useless quantity because it
    does not measure the dilution of precision of any physical quantity.
     
    David L. Wilson, May 16, 2009
    #12
  13. Johnson

    T Driver Guest

    On May 15, 5:35 pm, "David L. Wilson" <> wrote:
    > >"T Driver" <> wrote in message
    > >news:....

    >
    > On May 14, 4:13 pm, "David L. Wilson" <> wrote:
    >
    >
    >
    > >> "T Driver" <> wrote in message

    >
    > >>news:....
    > >> On May 13, 5:23 pm, "David L. Wilson" <> wrote:

    >
    > >> > "Sam Wormley" <> wrote in message

    >
    > >> >news:qWFOl.697079$yE1.166398@attbi_s21...

    >
    > >> > > Johnson wrote:
    > >> > >> I would like to know in general which one is typically chosen to
    > >> > >> indicate
    > >> > >> the quality of DOP and GPS accuracy, PDOP or GDOP?

    >
    > >> > >http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html

    >
    > >> > > PDOP = Position Dilution of Precision (3-D), sometimes the Spherical
    > >> > > DOP.
    > >> > > HDOP = Horizontal Dilution of Precision (Latitude, Longitude).
    > >> > > VDOP = Vertical Dilution of Precision (Height).
    > >> > > TDOP = Time Dilution of Precision (Time).

    >
    > >> > > I use PDOP and HDOP

    >
    > >> > Amd it is probably worth mentioning the GDOP is a term that refers to
    > >> > all
    > >> > of
    > >> > these--they are all geometry only estimates of relative precison.. So
    > >> > the
    > >> > choice is never between PDOP and GDOP ) as in the orignal post
    > >> > question)
    > >> > as
    > >> > PDOP is "one of the kinds of GDOP". (The webpage calls the above
    > >> > "components" of GDOP but they are not components in the usual sense.)

    >
    > >>> You can think of DOP along each coordinate axis, so that in a North-
    > >> East-Down reference frame there is a North DOP, an East DOP as well as
    > >> the vertical DOP.
    > >> HDOP = sqrt( northDop^2 + eastDOP^2)
    > >> PDOP = sqrt(HDOP^2 + VDOP^2)
    > >> Finally, GDOP = sqrt(PDOP^2 + TDOP^2)

    >
    > >> I have not seen the last equation and it has a problem in that exactlyin
    > >> what units of what measurement is it a Dilution of Precision? Most people
    > >> use GDOP as a general term for geometric dilution of precision of which
    > >> the
    > >> other DOP's are types of.

    > >DOP has no units.  This confuses people sometimes, as you can become
    > >accustomed to associating DOP with your navigation accuracy 1-for-1.
    > >With that assumption, some might think DOP would have the units of
    > >meters.  Navigation accuracy actually takes into account the
    > >pseudorange errors as well, which is where the length units come in.
    > >See the Position Errors section here:
    > >http://blogs.agi.com/navigationAccuracy/?page_id=6
    > >Ted

    >
    > No confusion here.  Understood it has not units but it is meant to be a
    > dilution of precision due to satellite geometry and only so on a statistical
    > basis.  GDOP is the general term for HDOP, PDOP, and TDOP but to consider
    > GDOP as a RMS of PDOP and TDOP yeilds a really useless quantity because it
    > does not measure the dilution of precision of any physical quantity.


    Absolutely agree, which is why it is rarely used. Most of the GPS
    references define it this way however.
     
    T Driver, May 16, 2009
    #13

  14. >"T Driver" <> wrote in message
    >news:...

    On May 15, 5:35 pm, "David L. Wilson" <> wrote:
    >>
    >> >"T Driver" <> wrote in message
    >> >news:...

    >>
    >> On May 14, 4:13 pm, "David L. Wilson" <> wrote:

    ....
    >>
    >> No confusion here. Understood it has not units but it is meant to be a
    >> dilution of precision due to satellite geometry and only so on a
    >> statistical
    >> basis. GDOP is the general term for HDOP, PDOP, and TDOP but to consider
    >> GDOP as a RMS of PDOP and TDOP yeilds a really useless quantity because
    >> it
    >> does not measure the dilution of precision of any physical quantity.


    >Absolutely agree, which is why it is rarely used. Most of the GPS
    >references define it this way however.


    Probably though worth noting that the SPS Specification defines DOP. HDOP,
    PDOP, and TDOP but makes no reference to the acronym GDOP at all.
     
    David L. Wilson, May 16, 2009
    #14
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    Replies:
    7
    Views:
    495
    Richard Owlett
    May 12, 2005
  3. Jeroen Bezemer

    Different Pdop

    Jeroen Bezemer, May 7, 2005, in forum: Global Navigation Satellite Systems
    Replies:
    7
    Views:
    622
    Richard Owlett
    May 12, 2005
  4. Looking for a simple way to calculate PDOP

    , May 5, 2009, in forum: Global Navigation Satellite Systems
    Replies:
    4
    Views:
    1,236
  5. Sam Wormley

    short period of high HDOP/PDOP on the 11th of September

    Sam Wormley, Sep 11, 2009, in forum: Global Navigation Satellite Systems
    Replies:
    0
    Views:
    349
    Sam Wormley
    Sep 11, 2009
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