CH Geodesy & Coordinate Systems 4

Question 1

A hydrographer is given coordinates in EPSG:4326. What coordinate reference system do these values represent?

Accepted Answer

WGS 84 geographic (degrees)

Answer

EPSG:4326 is the code for the WGS 84 geographic coordinate reference system using latitude and longitude in decimal degrees.

Question 2

What is the maximum angular zone width of a single UTM zone?

Accepted Answer

6°

Answer

Each of the 60 UTM zones spans exactly 6° of longitude, numbered 1 through 60 starting at 180°W.

Question 3

When computing the grid azimuth from a geodetic azimuth in UTM, which correction must be applied?

Accepted Answer

Meridian convergence (γ)

Answer

Meridian convergence γ is the angle between grid north and geodetic (true) north at any point off the central meridian; grid azimuth = geodetic azimuth − γ.

Question 4

Which reference frame is the closest practical realization of WGS 84 for precise hydrographic work in the US?

Accepted Answer

NAD 83 (2011) epoch 2010.0

Answer

NAD 83 (2011) at epoch 2010.0 is the current national adjustment, and its agreement with WGS 84 is typically better than 1 m, making it the practical WGS 84 realization for US surveys.

Question 5

A geodetic baseline measured along the Earth's surface is 10 000 m. What type of line connects the two endpoints with the shortest path on the ellipsoid?

Accepted Answer

Geodesic

Answer

A geodesic (or geodetic line) is the shortest path between two points on the surface of an ellipsoid, analogous to a great circle on a sphere.

(CH) Certified Hydrographer Practice Test

(CH) Certified Hydrographer Practice Test

CH Geodesy & Coordinate Systems 4