GPS position fix indicator criteria

2 thoughts on “GPS position fix indicator criteria

  1. We are using the Jupiter JF2 and are monitoring the position fix indicator, a register that indicates:


    0 – no GPS fix

    1 – GPS fix

    2 – DGPS fix



    My question is about the conditions necessary for states ‘1’ and ‘2’. How many satellites must have been in view before a GPS fix is declared? The NMEA manual gives the caveat that this "includes the minimum number of satellites required, any DOP mask setting, presence of DGPS corrections, etc."


    Are the parameters for minimum number of satellites required and DOP mask directly readable and settable by users?



    1. Dear Brent,


      normally the indicator 1, appers when the receiver is able to perform a Fix.

      That is an example:


      Here is one indicating a regular GPS fix




      Here is one indicating a fix with DGPS included





      The indicator 2 – DGPS Fix is that related to the capability to perform a Fix by using also the standard GPS constallation in view but also with the auxiliary of DGPS satellites.

      The DGPS is not enable by default and it’s possible to enable it on OSP mode. However the functionaly of DGPS, it depends from which region where you are, because there are different kind of DGPS signal.


      EGNOS: Europe


      WAAS etc…


      Please have a look at the attached picture.


      The SiRFIV, (JF2) has the capatibility to perform 2D fix and 3Dfix. Obviously the 3D-fix is more accurated because required at least 4-5 satellites and also it will report nice value od HDOP.