FIX
Constrains to fixed height or position
Platform: |
OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7, SMART2 |
This command is used to fix height or position to the input values. For various applications, fixing these values can assist in improving acquisition times and accuracy of position or corrections. For example, fixing the position is a requirement for differential base stations as it provides the reference position to base the differential corrections from.
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Error checking is performed on the entered fixed position by the integrity monitor. Depending on the result of this check, the position can be flagged with the following statuses.
-
SOL_COMPUTED: The entered position has been confirmed by measurement.
-
PENDING: Insufficient measurements are available to confirm the entered position.
-
INTEGRITY_WARNING: First level of error when an incorrect position has been entered. The fixed position is off by approximately 25-50 metres.
-
INVALID_FIX: Second level of error when an inaccurate position has been entered. The fixed position is off by a gross amount.
An incorrectly entered fixed position will be flagged either INTEGRITY_WARNING or INVALID_FIX. This will stop output of differential corrections or RTK measurements and can affect the clock steering and satellite signal search. Checks on the entered fixed position can be disabled using the RAIMMODE command.
Message ID: 44
Abbreviated ASCII Syntax:
FIX type [param1 [param2 [param3]]]
Factory Default:
FIX none
ASCII Example:
FIX none
FIX HEIGHT 4.567
FIX position 51.116 -114.038 1065.0
In order to maximize the absolute accuracy of RTK rover positions, the base station coordinates must be fixed to their known position using the FIX POSITION [lat][lon][hgt] command.
Field |
Field Type |
ASCII Value |
Binary Value |
Description |
Format |
Binary Bytes |
Binary Offset |
1 |
Command header |
- |
- |
FIX header This field contains the command name for abbreviated ASCII or the message header for ASCII (see page 1) or Binary (see page 1). |
- |
H |
0 |
2 |
type |
See Table: Fix Types |
Fix type |
Enum |
4 |
H |
|
3 |
param1 |
Parameter 1 |
Double |
8 |
H + 4 |
||
4 |
param2 |
Parameter 2 |
Double |
8 |
H + 12 |
||
5 |
param3 |
Parameter 3 |
Double |
8 |
H + 20 |
ASCII Type Name |
Parameter 1 |
Parameter 2 |
Parameter 3 |
AUTO |
Not used |
Not used |
Not used |
HEIGHT |
Default MSL height 1 (-1000 to 20000000 m) |
Not used |
Not used |
NONE |
Not used |
Not used |
Not used |
POSITION |
Lat (-90 to 90 degrees) where a ‘-’ sign denotes south and a ‘+’ sign denotes north |
Lon (-360 to 360 degrees) where a ‘-’ sign denotes west and a ‘+’ sign denotes east |
Default MSL height 1 (‑1000 to 20000000 m) |
For a discussion on height, refer to An Introduction to GNSS available on our website at novatel.com/an-introduction-to-gnss.
ASCII Name |
Binary Value |
Description |
NONE |
0 |
Unfix. Clears any previous FIX commands |
AUTO |
1 |
Configures the receiver to fix the height at the last calculated value if the number of satellites available is insufficient for a 3-D solution. This provides a 2-D solution. Height calculation resumes when the number of satellites available allows a 3-D solution |
HEIGHT |
2 |
Configures the receiver in 2-D mode with its height constrained to a given value. This command is used mainly in marine applications where height in relation to mean sea level may be considered to be approximately constant. The height entered using this command is referenced to the mean sea level, see the BESTPOS log (is in metres). The receiver is capable of receiving and applying differential corrections from a base station while fix height is in effect. The fix height command overrides any previous FIX HEIGHT or FIX POSITION command. This command only affects pseudorange corrections and solutions. |
POSITION |
3 |
Configures the receiver with its position fixed. This command is used when it is necessary to generate differential corrections. For both pseudorange and differential corrections, this command must be properly initialized before the receiver can operate as a GNSS base station. Once initialized, the receiver computes differential corrections for each satellite being tracked. The computed differential corrections can then be output to rover stations using the RTCMV3 differential corrections data log format. See Transmitting and Receiving Corrections for information about using the receiver for differential applications. The values entered into the fix position command should reflect the precise position of the base station antenna phase center. Any errors in the fix position coordinates directly bias the corrections calculated by the base receiver. The receiver performs all internal computations based on WGS84 and the DATUM command is defaulted as such. The datum in which you choose to operate (by changing the DATUM command) is internally converted to and from WGS84. Therefore, all differential corrections are based on WGS84, regardless of your operating datum. The FIX POSITION command overrides any previous FIX HEIGHT or FIX POSITION command settings. |