SAM-M10Q-Integration manual
Figure 17: PL bounding true position error
2.11.2 Interface
The protection level bounds the true position error with a target misleading information risk (TMIR),
for example 5[%MI/epoch] (read: 5% probability of having an MI per epoch). The target misleading
information risk describes the probability per epoch of having misleading information (MI), meaning
that it is not possible to bound the true position error because it is larger than the protection level
(see Figure 18).
Figure 18: Misleading information
The output of the protection level is published through the UBX-NAV-PL message.
TMIR is specified in one dimension for PL. It is not specified as a horizontal 2D or 3D value.
The protection level values (UBX-NAV-PL.plPos1/2/3) are confidence intervals around the
reported position (for example, UBX-NAV-PVT or UBX-NAV-HPPOSLLH).
The target misleading information risk is provided in exponential notation (UBX-NAV-
PL.tmirCoeff and UBX-NAV-PL.tmirExp), for example UBX-NAV-PL.tmirCoeff = 5 and UBX-
NAV-PL.tmirExp = 0 results in 5e0 (= 5).
The true position error is generally unknown, unless a very accurate and reliable truth
positioning system is reporting an estimate for the true position.
When the GNSS environment deviates significantly from the normal mode of operation as compared
to scenarios where the PL has been validated, a validity flag is set to false to indicate these
UBX-22020019 - R01
2 Receiver functionality Page 43 of 72
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