What is MPEE (multipath error envelope)

Technical details of the Multipath Error Envelope (MPEE).

1. Multipath Interference:
   • Multipath interference occurs in satellite navigation systems (such as GPS) when signals from satellites reach the receiver via multiple paths.
   • These paths can include direct line-of-sight paths as well as paths involving reflections from nearby buildings, terrain, or other objects.
   • When multipath interference occurs, the received signals can be distorted and delayed, leading to errors in the calculated position.
2. Importance of MPEE:
   • The MPEE represents the bounds of the errors caused by multipath interference.
   • It provides an estimate of the maximum potential error that can be introduced into the position calculation due to multipath effects.
   • In other words, the MPEE defines the uncertainty region around the true position due to multipath.
3. Calculation of MPEE:
   • To calculate the MPEE, several factors are considered:
     • Environment Characteristics: Presence of buildings or objects causing reflections.
     • Receiver Properties: Signal power, signal-to-noise ratio, receiver sensitivity.
     • Satellite Signals: Geometry of satellites in view.
   • Field testing is commonly used to estimate the MPEE. By comparing receiver measurements to ground truth positions under various conditions, data on position variations due to multipath interference is collected.
4. Representation:
   • The MPEE is typically expressed in terms of a distance (e.g., meters or feet).
   • It represents the radius of a circle or sphere centered on the true position.
   • Within this envelope, the actual position may lie due to multipath effects.