How does satellite elevation influence the severity of tropospheric delay?

• A. Higher elevation angles experience more delay.
• B. Elevation has no effect on tropospheric delay.
• C. Lower elevation angles experience more pronounced tropospheric delay.
• D. Elevation only affects ionospheric delay.

Answer: (C)

The main idea is that tropospheric delay depends on the path length through the atmosphere. When a satellite is low on the horizon, the signal travels through a longer slant path in the troposphere, so more air and water vapor affect it, increasing the delay. Conversely, when the satellite is high in the sky, the path through the troposphere is shorter, and the delay is smaller. In practice, the zenith (straight overhead) delay is scaled to the actual slant path by a mapping function that grows as elevation decreases, so the delay rises quickly as you move toward lower elevations. The tropospheric delay has dry and wet components, both proportional to the path length, with the wet part being more variable due to humidity but still larger when the signal traverses more atmosphere. So lower elevation angles experience more pronounced tropospheric delay, while higher elevations reduce it. Elevation affects tropospheric delay, not just ionospheric delay.