Kinematic Precise Point Positioning During Marginal Satellite Availability

Precise Point Positioning (PPP) is a technique where observations from a single GNSS receiver are used to estimate coordinates with precision ranging from centimeters to decimeters. PPP does not rely on data from dedicated reference receivers and is logistically a very competitive alternative to differential GNSS methods. In areas with reduced satellite availability the geometrical strength of the solution will be reduced and observations from such periods should be treated with special attention. In marine applications the use of additional information in the form of height constraints will enhance PPP during periods with marginal satellite availability. Additional observations from GLONASS satellites or Inertial Navigation System (INS) will also to a certain degree compensate for reduced availability of GPS satellites. This paper addresses the contribution from height aiding and from current GLONASS satellites. Based on formal precision and reliability as well as accuracy both height aiding and GLONASS improve the quality of estimated coordinates. The contribution to reliability is more significant than the contribution to precision and accuracy. In periods with very weak GPS constellation, height aiding gives the most valuable contribution. The paper verifies that even under marginal satellite availability, PPP processing is capable of producing coordinates with precision and accuracy at the subdecimeter level and with reliability at the one meter level.