SUR 2101 Geomatics
QUIZ 2 - KEY
Answer all questions.1
1. When a measurement is given in different units, such as degrees, minutes and
seconds, how are significant figures determined? [2]
By converting the measurement to the smallest unit and looking at the significant
figures for that number.
2. How many significant figures in the azimuth 205025โ08โ? [2]
Converts to 739,508โ โฆ so 6 sig figs.
3. What kind of map projection (e.g. Lambert conformal conic, transverse Mercator,
Albers equal area) would you recommend for the state of California state plane
coordinate system? [2]
Transverse Mercator โฆ because scale is true in a N-S direction.
4. How does an EDM figure out how many whole wavelengths there are when
measuring between two points? [5]
It uses signals with different wavelengths. Long wavelengths are used to get an
approximate distance and then shorter wavelengths are used to get more precision on
this measurement.
5. What is the name of the equipotential surface perpendicular to gravity that
approximates mean sea level? [2]
The Geoid.
6. If you measure the following two zenith angles on direct (D) and reverse (R), what is
the index error of the instrument? What is the reason for this error? [4]
(D) 890 35โ45โ (R) 2700 24โ05โ
Sum of the two angles = 3590 59โ50โ therefore index error = ยฝ (10) = 5โ
2. Name two major differences between a CORS network and a HARN? [4]
CORS is an active station with a GPS set up on it, whereas a HARN point is a passive
monument in the ground (no GPS).
CORS is national while HARN is regional.
3. What is the expected error in an EDM with an accuracy specification of 10mm +
20ppm over a measured distance of 3,500 meters? [3]
Error = 10 + 20 (3500/1000) = 80 mm (assuming both systematic errors)
4. What signals are emitted from a standard dual frequency GPS receiver? [2]
1 You are given the following formulae: E = mc2 DX = D Sin ๏ก DY = D Cos ๏ก
1
