CST GPS & GNSS Surveying Technologies 2

Question 1

Which GPS error source is caused by satellite signals reflecting off buildings or other surfaces before reaching the receiver antenna?

Accepted Answer

Multipath error

Answer

Ionospheric delay

Answer

Tropospheric delay

Answer

Satellite clock error

Question 2

How does the ionosphere primarily affect GPS signal accuracy?

Accepted Answer

It slows the signal and introduces ranging errors proportional to electron content

Answer

It blocks the signal completely under heavy solar activity

Answer

It changes the carrier frequency of the signal

Answer

It rotates the signal's polarization, causing antenna mismatch

Question 3

Which receiver capability most effectively eliminates ionospheric delay errors in GPS surveys?

Accepted Answer

Dual-frequency capability measuring L1 and L2 simultaneously

Answer

A large ground plane antenna

Answer

Reducing the total observation session length

Answer

Increasing the elevation mask angle above 20 degrees

Question 4

Why do GPS surveyors set an elevation mask angle, typically between 10 and 15 degrees?

Accepted Answer

To exclude low-angle satellites whose signals traverse more atmosphere and are prone to multipath

Answer

To restrict data collection to periods of low sun angle

Answer

To limit the vertical range of the antenna tilt sensor

Answer

To define the maximum terrain slope for kinematic surveys

Question 5

What is ephemeris error in GPS, and what causes it?

Accepted Answer

Inaccuracy in the broadcast satellite orbital position and velocity data

Answer

Receiver clock drift caused by temperature fluctuations

Answer

Antenna phase center offset from the physical antenna mount

Answer

Signal degradation caused by moisture on the antenna radome

Question 6

What is the purpose of setting a minimum PDOP threshold in GPS data collection?

Accepted Answer

To guarantee that only observations with favorable satellite geometry are accepted

Answer

To ensure the receiver records a minimum number of epochs per point

Answer

To set the antenna height cutoff for leveling tolerance

Answer

To filter out data collected during periods of rain

Question 7

Which network-based service creates a virtual GPS base station near the rover using data from multiple permanent reference stations, delivering RTK corrections via cellular network?

Accepted Answer

VRS (Virtual Reference Station) network

Answer

WAAS (Wide Area Augmentation System)

Answer

DGPS marine beacon service

Answer

LORAN-C radionavigation