CST GPS & GNSS Surveying Technologies 3

Question 1

In RTK GPS surveying, what must be successfully completed before the receiver can deliver centimeter-level accuracy?

Accepted Answer

Integer ambiguity resolution (initialization)

Answer

RTK GPS requires integer ambiguity resolution — determining the exact whole number of carrier wave cycles between each satellite and the antenna — before centimeter-level accuracy is achievable; until then, only a less accurate 'float' solution is available.

Question 2

What is a CORS station in the context of GPS surveying infrastructure?

Accepted Answer

A Continuously Operating Reference Station providing permanent GPS data

Answer

CORS (Continuously Operating Reference Station) are permanently installed GPS receivers that collect data 24/7, forming networks that support post-processing, real-time corrections, and national spatial reference infrastructure.

Question 3

When converting GPS ellipsoidal heights to orthometric (mean sea level) heights, what resource does a surveyor use?

Accepted Answer

A geoid undulation model such as GEOID18

Answer

GPS measures heights above the WGS 84 ellipsoid, while engineering and construction require orthometric heights above the geoid (mean sea level); NGS geoid models like GEOID18 provide the geoid-ellipsoid separation (N) needed for conversion.

Question 4

Which primary operational advantage does GNSS offer over traditional total station traversing on large-scale projects?

Accepted Answer

GNSS allows positions to be determined without intervisibility between stations

Answer

Unlike total station surveys that require unobstructed sightlines between consecutive points, GNSS receivers determine positions independently anywhere with a clear view of the sky, greatly increasing efficiency on large or obstructed sites.

Question 5

During an RTK GPS survey, the PDOP value rises to 9.2. What is the appropriate course of action?

Accepted Answer

Suspend observations and wait for satellite geometry to improve

Answer

A PDOP above 6 indicates poor satellite geometry that significantly degrades positional accuracy; observations should be suspended until PDOP drops to an acceptable level (typically below 4) to ensure reliable results.

CST - Certified Survey Technician Practice Test

CST - Certified Survey Technician Practice Test

CST GPS & GNSS Surveying Technologies 3