Fundamental Concepts in Geodesy and Surveying
Core Surveying Principles and Techniques
- Where are geodetic coordinates located? On an ellipsoid of revolution.
- When is the error in azimuth angle measurements less? When the distance is farther.
- What tachometer condition prevents it from working correctly? Lack of perpendicularity between the main shaft and the countershaft.
- What is geographic latitude? The meridian arc between the Equator and the parallel passing through the point.
- What conditions must be met at the start of a tachymeter station? The instrument must be level, and the main spindle (vertical axis) must pass through the station point.
- When using the radiation method, which points are not advisable to survey? Points distant from the station that are very close together.
- In an itinerary (traverse) with a total station, how are angular errors handled? They are always transmitted from one station to the next.
- What are systematic errors in altimetry? Non-parallelism of level surfaces, atmospheric refraction, and Earth’s curvature.
- How does the planimetric (e.g., agricultural) area relate to the actual surface area? It is less than or equal to the actual surface area.
- If magnetic declination is 6.5g West, what is the orientation between the point and magnetic north? The alignment towards magnetic north is oriented N-6.5g (or has an azimuth of 393.5g).
- How does the maximum permissible error relate to survey scale? It is lower (stricter) for higher scales (larger scale maps/plans).
- What references can be used for measuring vertical angles? Heights above the horizon or zenith distances.
- How is the latitude of a point defined? As the meridian arc between the Equator and the parallel passing through the point.
- Describe the Universal Transverse Mercator (UTM) map projection. It uses a secant cylinder aligned with meridians to project points from the ellipsoid according to a specific analytical law, preserving angles locally (conformal).
- What defines the start station setup for a tachometer? Simultaneous fulfillment that the instrument is level and the main spindle passes through the station point.
- Rank these planimetric methods by descending precision: Itinerary (traverse), intersection, and radiation.
- When is the radiation method less suitable for point selection? For points far from the station that are also very close to each other.
- How do angular errors propagate in a total station itinerary? They are always transmitted from each station to the subsequent stations in the itinerary.
- What is the contrast between direct intersection and resection (reverse intersection)? In resection, the instrument is stationed only at the unknown point(s).
- When are intersection errors maximum based on the angle at the unknown point? Errors are maximum when the intersection angle is small (e.g., below 25g) or large (e.g., exceeds 175g).
- If magnetic declination is 8g West, what is the azimuth of the alignment towards magnetic north? It has an azimuth of 392g (assuming 400g circle and Geographic North as 0g/400g).
- Where is the influence of Earth’s curvature greater? In altimetry (height measurements).
- What is the key difference between a map and a plan? Maps require a map projection to account for Earth’s curvature over larger areas, while plans typically represent smaller areas orthographically without projection.
- What property does a conformal projection preserve? Angles.
- How does survey tolerance relate to scale? Tolerance is generally stricter (smaller allowable error) for larger scales.
- If the permissible error for precision geometric leveling is 1 mm per km, what is the tolerance for a 100 km traverse? The tolerance is typically calculated as error rate * sqrt(distance), so 1 mm/sqrt(km) * sqrt(100 km) = 10 mm.
- When is a total station considered oriented? When its horizontal circle is set to correspond to a known azimuth or reference direction (e.g., by backsighting a known point).
- What is the origin of longitudes? The Prime Meridian, which passes through Greenwich, England.
- What is the definition of a meridian line on the ground at a point? It is the intersection of the tangent plane to the ellipsoid at that point and the meridian plane passing through that point.
- What surveying technique is used to mark project boundaries in the field? Stakeout (or setting out).
- Which leveling method avoids measuring the instrument height for each setup? Differential leveling, particularly using the midpoint method (equal backsight and foresight distances).
- How is the closing error in a traverse typically handled? It is distributed (adjusted) proportionally among the measurements according to established rules.
- How are level surfaces defined? As equipotential surfaces of the Earth’s gravity field (surfaces where gravity potential is constant).
- In a direct-reading traverse with a total station, what should the orientation correction be? If the instrument is correctly oriented at each station setup, the orientation correction should ideally be zero.
- Which planimetric method allows for the calculation of a closure error? Itinerary (traverse).
- What is the difference between direct intersection (forward) and resection (reverse)? In resection, the instrument is stationed only at the unknown point whose coordinates are to be determined.
- How is absolute orientation achieved in photogrammetry? By relating the stereomodel to the ground coordinate system using measured coordinates of ground control points (GCPs).
- How is correct orientation established in the radiation method? By sighting (observing) a point or direction with a known azimuth from the instrument station.
- What does the altimetry tolerance in a survey often depend on? It often depends on the required contour interval (equidistance) or specific project accuracy requirements.
- What is the final level platform achieved by earthwork called? The subgrade or formation level (often referred to as grade).
- What are the main axes of a total station? The vertical axis (primary axis or standing axis), the horizontal axis (secondary axis or trunnion axis), and the collimation axis (line of sight).