Question

Which of the following statement(s) concerning GNSS errors is/are CORRECT?

• A. Tropospheric delay increases with increasing relative humidity
• B. Ionospheric error is highly correlated with the position of the Moon
• C. Multipath error is caused by buildings and man-made features and not by vegetation
• D. The observed range is called pseudorange because of its erroneous nature

Hint:

Remember: ionosphere $⇒$ Sun-driven; troposphere (wet) $⇒$ humidity; multipath $⇒$ any reflecting/scattering environment; pseudorange $⇒$ geometric range $+$ errors.

Answer 1

The Correct Option is A

(A) True. Tropospheric delay has a dry (hydrostatic) and a wet component; the wet component grows with water vapour content $⇒$ higher relative humidity increases delay.
(B) False. Ionospheric delay is driven mainly by solar radiation and geomagnetic activity (diurnal/solar-cycle dependence), not the Moon’s position.
(C) False. Multipath arises from reflections/scattering from any nearby surface—buildings, metallic structures, ground, and also vegetation (leaves/branches). Vegetation can and does cause multipath (though often weaker).
(D) True. Code-based measured range includes receiver/satellite clock biases and propagation errors, so it is not the true geometric range; hence the term pseudorange.