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NMEA Position and Heading (No CheckSum) - 12

Description

  • Position data
    The driver will automatically detect the position format from the first NMEA position sentence supported.
    Driver will decode following NMEA sentences, containing (GPS or RTK) position data:
    • $--GGA,
    • $--RMC,
    • $--GGK, or
    • $--GLL
  • Quality
    Driver can be used to decode quality information from NMEA sentences.
    It will automatically decode the supported NMEA quality sentences and copy the values to the previously decoded position data buffer. The driver decodes:
    • $--GST,
    • $--GSA
    • $PDAS,QUAL,
  • Heading
    Driver will automatically detect the heading format from the first NMEA gyro string.
    The driver is able to decode heading from NMEA sentences:
    • $--HDT,
    • $--HDG,
    • $--HDM
  • Communication
    The driver does not actively communicate with the positioning system;it listens to the incoming messages.
    Two communication versions of the driver are available, but the internal workings of the drivers are the same except for the data reception:
    • Serial
    • Network version (UDP).
  • Timing
    The time tag of (all) the data is determined from the position sentence, i.e. the time tag of the (first) heading (after the position data) is copied from the position buffer update time. However, the data buffers are not updated until the last sentence from an NMEA block is received. NMEA blocks are determined as follows:
  • Auto-Detection of NMEA Formats
    1. After starting up, or after a "Reset I/O" command has been issued by the QINSy Controller, the driver waits for the first NMEA position sentence that can be properly decoded. The NMEA type of this sentence will determine the next NMEA position sentences that are decoded.
    2. All NMEA quality information sentences and NMEA gyro compass sentences that are received before the second NMEA position sentence will be considered to be part of one NMEA block.
    3. The format of the last NMEA quality information sentence or NMEA gyro compass sentence will be used to define the NMEA sentence that will trigger an update of the driver data buffers. There is a command line option to disregard gyro compass sentences as trigger strings.
    4. If only NMEA position sentences are received (during the auto-detection phase), then the driver position data buffer is updated for each valid NMEA position sentence of the right format.
    5. Be aware that the auto-detection process will take at least two valid position sentences (twice the position update cycle time) after starting up the driver.
    6. The auto-detection process will be restarted after each "Reset I/O" command.
  • Warnings

    Update Rates
    This driver can be used when an NMEA position, NMEA quality sentence(s) and NMEA heading are received on the same port and at the same update rate
    If the gyro is updating faster than the positions, then the data have to be split and separate position and gyro systems have to be defined on separate ports.
    The driver also assumes that the position sentence is output first, before quality and gyro heading.

Driver Information

Driver NMEA Position and Heading /
POS M-V
Interface Type Serial/UDP  Driver Class Type Terminated 
UTC Driver (question) No Input / Output Input  Executable

DrvPositionNMEA.exe
DrvPositionNMEAUDP.exe

Related Systems
Related Pages  



Decoding Notes

Driver will not decode any xxGGA, xxGLL or xxGGK strings if the position fields are empty.

Format
$GPGGA,,,,,0,00,1.0,00065.000,M,00000.000,M,0.00,*4D
Format Example
$INRMC,112545,A,2637.9681,N,05009.4071,E,00.0,182.3,240500,,*38<CR><LF>

$PTNL,GGK,172814.00,071296,3723.46587704,N,12202.26957864,W,3,06,1.7,EHT-6.777,M*48

$GPGGA,072840.20,5352.726971,N,00842.847935,E,0,00,1.0,00065.000,M,00000.000,M,0.00,*4D
$HEHDT,226.2,T*2B

$INGGA,120000.045,4928.46282,N,00008.01717,E,4,00,1.0,55.14,M,,,2.0,0001*34
$INGST,120000.045,,0.7,0.6,88.1,0.7,0.7,0.7*6C
$INGSA,A,3,1,3,5,7,9,11,13,15,,,,,1.1,2.2,3.3
$INHDT,52.7,T*15

$GPGGA,104101.07,5149.695871,N,00443.244094,E,19,06,2,13.864,M,47.176,M,1.0,0001
$PDAS,QUAL,0.018,0.018,0.023,5

$GLL,0447.01472,S,01151.07695,E,05,D,9,ID1
$HCHDM,162.3,M*2F

System Configuration

Driver can be used to decode '$PDAS,QUAL' quality messages after enabling them in a DSNP Aquarius RTK receiver by defining the following string in its Configuration Setup (KART Real Time solution):

'$PDAS,QUAL',',NPKRSD:1:3,',',EPKRSD:1:3,',',HPKRSD:1:3,',',MKIN

Database Setup

The "NMEA Position + Heading ($xxGGA/$xxHDT)" and "POS M/V (NMEA GGA GST GSA + HDT)" entries have been retained for backwards compatibility. They are the same as the "CheckSum" driver.

  • Heading
    When the NMEA input data block also contains a $xxHDT, $xxHDG or $xxHDM sentence, the driver can also be used to decode the heading data. The driver currently only supports True Heading observations. If a HDM heading is obtained, magnetic variation should be entered as for example a (C-O) value, with negative values for westerly variations, since (C-O) values are added to the raw heading observations, or a $xxHVD or $xxHVM sentence should be included. Values obtained from HDT and HDG strings are always true headings.
    • Add a system of type "Gyro's and compasses", select the same NMEA driver and enter the same serial I/O parameters as with the NMEA position driver. See the description under "GYRO SYSTEM DRIVERS". When this "NMEA Position + Heading" driver is used, a serial interface cable does not have to be split.

Online

  • Computation Setup


    In the Controller one can choose which positioning components need to be used in computation.
    • Unreliable Height - Tide
      This means that the height of the positioning system cannot be trusted and that tide will be used as alternative height source.
    • Accurate height - RTK
      This means that the height reported by the positioning system is accurate and will be used as height component.
    • Standard Deviations
      The standard deviations (SD's) are used as Quality Indicators in the computation and for the TPU calculations. There are 3 options:
      • System Driver
        The reported SD's by the positioning system (in the $xxGST string) will be used when available. This means that the realtime SD's are used and these are the best option to get a more realistic view on the performance of your survey system.
      • Computation Setup
        These are the values entered in the computation in the fields: Position a priori SD and Height a priori SD (only in Accurate Height, otherwise SD of the Tide observation will be used).
        These values are predefined values by the manufacturer or by experience when using them in a static environment. They represent accuracies that can be achieved when the equipment is working accordingly.
      • Database Setup
        This is the value entered in Database Setup on page 2 of the device setup, under Position Parameters: A-priori SD.
        This value will online be used:
        • Position a priori SD = value
        • Height a priori SD = 2x value (only in Accurate Height, otherwise SD of the Tide observation will be used).
  • $xxGST and/or $xxGSA


    • Positioning System Display
      The statistical information from $xxGST and $xxGSA sentences are shown in a Positioning System Display.
      The RMS value of the range inputs from the $xxGST sentence is displayed in the MDE box.
      The age of the DGPS data from the $xxGGA sentence is displayed in the Unit Variance box.
      When no $xxGSA sentence is available, the Satellites tab just indicates the number of satellites in use (decoded from $xxGGA sentence).

    • Observation Physics Display
      The standard deviations of the latitude, longitude and altitude (height) errors are shown in an Observation Physics Display as the so-called quality indicator of the corresponding positioning system observation.



    • Alert Display
      The various statistical measures can be used to define an alert and even to pause storage when such a value is above a certain limit. Start up an Alert Display and add an alert of type "Raw Data Alert".
      Possible alerts:

      Raw Data - Type

      Explanation

      $--GGA

      $--GST

      $--GSV

      Position mode outside limits

      alert on GNSS (RTK) solution mode value

      (tick)

      (error)

      (error)

      Differential Age above limit

      alert on age of GNSS corrections

      (tick)

      (error)

      (error)

      Number of Satellites outside limits

      Alert minimum required and maximum allowed satellites

      (tick)

      (error)

      (tick)

      Position RMS outside limits

      alert on semi-major axis value

      (error)

      (tick)

      (error)

      Quality indicator outside limits

      alert on standard deviation (SD) values

      (error)

      (tick)

      (error)


      The position mode and position RMS alerts can only be defined for the (positioning) system.
      The quality indicator (sd) alerts must be defined for the system and the specific observation, latitude, longitude or altitude (height).

      Raw Data - Type

      Alert Display Example

    • Time Plot Display
      The Time Plot Display can be used to show the standard deviations reported by the $--GST string.



    • Positioning System Display
  • $PDAS,QUAL

    • Positioning System Display
      The statistical information from $--GGA and $PDAS messages are shown in a Positioning System Display.
      The RMS value of the $--GGA position inputs from the $PDAS message is displayed in the 'Quality measures - a' box. The standard deviations of the latitude, longitude and altitude (height) values from the $PDAS messages are shown in the 'SD's - Latitude, Longitude, Height' boxes.
    • Observation Physics Display
      The standard deviations of the latitude, longitude and altitude (height) errors are shown in an Observation Physics Display as the so-called quality indicator of the corresponding positioning system observation.
    • Alert Display
      The various statistical measures can be used to define an alert and even to pause storage when such a value is above a certain limit. Start up an Alert Display and add an alert of type "Raw Data Alert". Possible alerts:

      Raw Data - Type

      Explanation

      Position mode outside limit

      alert on Kinematic Mode value in $PDAS message

      Position RMS outside limit

      alert on combined standard deviation value from $PDAS message

      Quality indicator outside limit

      alert on standard deviation (SD) value from $PDAS message

      The position mode and position RMS alerts can only be defined for the system.
      The quality indicator (sd) alerts must be defined for the system and the specific observation, latitude, longitude or altitude (height).

Drivers IO Notes

It is not advised to change the Driver.io options if you do not understand the impact of the changes. It's better to consult the Support department for a solid and durable solution.
The Drivers.io will be overwritten when installing a new QINSy version if the date of the last update of the existing file is older than the one in the new installation CD / MSI.

  • NOCS
    Command line parameter "NOCS" will disregard all checksum fields.
  • NOTH
    "NOTH" will not accept an NMEA gyro compass sentence as buffer update trigger sentence, i.e. the data buffers are updated after each NMEA position sentence (or accompanying quality sentence if one was encountered during auto-detection).
  • parameters "1", "2" or "3"
    Command line parameters "1", "2" or "3" are only applicable to GGA sentences.
    1. Add a "1" to the drivers.io command line to decode only the first field (if it is already the height above the ellipsoid),
    2. Add "2' to decode only the second field. Be aware that the command line for the corresponding entry for the heading driver must also be changed.
    3. Default is "3" which means that the height value is obtained as the sum of the first and second height fields in a GGA sentence, i.e. the antenna altitude field and the geoidal separation field.