The Troposphere is the neutral atmosphere comprising the lower 8km of the atmosphere. The Tropospheric Delay on GPS signals is of the non-dispersive variety because it is not frequency-dependent and hence impacts on both the L1 and L2 signals by the same amount (unlike that within the Ionosphere). The wet and dry components of the Troposphere cause the Delay to the signals, with the wet component be responsible for approximately 10% of the total delay. Various Tropospheric Delay models have been developed to estimate the Delay as a function of the satellite elevation angle, receiver height, and meteorological parameters such as temperature, pressure and humidity. The Delay in the Zenith direction is approximately 2.5m, increasing as the elevation angle of the satellite signal reduces. (This behaviour is described by the so-called Mapping Function, so that the Delay near the horizon is 3-5 times higher than in the Zenith direction.) The Delay is largely eliminated in Relative or Differential Positioning, however the residual Tropospheric Delay increases as the baseline length increases and may be a significant source of error (especially in the height component) for very high precision GPS Geodesy.

This definition is in context to GPS. See more contextual defintions for Troposphere, Tropospheric Delay.