RAIMMODE
Configures RAIM mode
|
Platform: |
OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7, SMART2 |
This command is used to configure Receiver Autonomous Integrity Monitoring (RAIM) operation. This command uses RTCA MOPS characteristics which defines the positioning accuracy requirements for airborne lateral navigation (LNAV) and vertical navigation (VNAV) at 3 stages of flight:
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En route travel
-
Terminal (within range of air terminal)
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Non-precision approach
In order to ensure that the required level of accuracy is available in these phases of flight, MOPS requires the computation of protection levels (HPL and VPL). MOPS has the following definitions that apply to NovAtel’s RAIM feature:
Horizontal Protection Level (HPL) is a radius of the circle in the horizontal plane. Its center is at the true position, that describes the region, assured to contain the indicated horizontal position. It is the horizontal region where the missed alert and false alert requirements are met using autonomous fault detection.
Vertical Protection Level (VPL) is half the length of the segment on the vertical axis. Its center is at the true position, that describes the region, assured to contain the indicated vertical position when autonomous fault detection is used.
Horizontal Alert Limit (HAL) is a radius of the circle in the horizontal plane. Its center is at the true position, that describes the region, required to contain the indicated horizontal position with the required probability.
Vertical Alert Limit (VAL) is half the length of the segment on the vertical axis. Its center is at the true position, that describes the region, required to contain the indicated vertical position with certain probability.
Probability of False Alert (Pfa) is a false alert defined as the indication of a positioning failure, when a positioning failure has not occurred (as a result of false detection). A false alert would cause a navigation alert.
Detection strategy
NovAtel’s RAIM detection strategy uses the weighted Least-Squares Detection (LSA) method. This method computes a solution using a LSA and is based on the sum of squares of weighted residuals. It is a comparison between a root sum of squares of residuals and a decision threshold to determine a pass/fail decision.
Isolation strategy
NovAtel RAIM uses the maximum residual method. Logically it is implemented as a second part of Fault Detection and Exclusion (FDE) algorithm for LSA detection method. Weighted LSA residuals are standardized individually and the largest residual is compared to a decision threshold. If it is more than the threshold, the observation corresponding to this residual is declared faulty.
The Detection strategy and Isolation strategy are used for all RAIM modes (USER, DEFAULT, APPROACH, TERMINAL and ENROUTE.
Message ID: 1285
Abbreviated ASCII Syntax:
RAIMMODE mode [hal [val [pfa]]]
Factory Default:
RAIMMODE default
Input Example:
RAIMMODE user 100 100 0.01
RAIMMODE terminal
|
Field |
Field Type |
ASCII Value |
Binary Value |
Description |
Format |
Binary Bytes |
Binary Offset |
|
1 |
Command header |
- |
- |
RAIMMODE header This field contains the command name for abbreviated ASCII or the message header for ASCII or Binary. |
- |
H |
0 |
|
2 |
MODE |
When the MODE is set to DEFAULT, protection levels are not calculated meaning that values for HAL and VAL are set to the maximum. |
Enum |
4 |
H |
||
|
3 |
HAL |
5 ≤ HAL ≤ 9999.99 |
Horizontal alert limit (m) (Default = 9999.99) |
Double |
8 |
H+4 |
|
|
4 |
VAL |
5 ≤ VAL ≤ 9999.99 |
Vertical alert limit (m) (Default = 9999.99) |
Double |
8 |
H+12 |
|
|
5 |
PFA |
(Pfa) = 1e-7≤ Pfa ≤ 0.25 |
Probability of false alert (Default = 0.001) |
Double |
8 |
H+20 |
|