Types of Surveying: Geodetic and Plane
Surveying methods are grouped into two main types: Geodetic Surveying and Plane Surveying. The difference is how they treat the Earth’s shape.
Geodetic Surveying
In geodetic surveying, we take the Earth’s curve into account. Calculations are done on an ellipsoid (a slightly flattened sphere) that closely matches the size and shape of our planet.
Simple Explanation: Imagine trying to map a giant ball. You need special math to place points correctly over long distances, because on a curved surface, straight lines on a map aren’t really straight on the ground.
- Used for finding positions of points that are far apart (long lines).
- Creates reference monuments that help with smaller, local surveys.
- Early methods used precise theodolites (angle-measuring tools) and metal tapes with low expansion.
- Modern methods use GNSS (Global Navigation Satellite Systems) for faster, more accurate results.
Plane Surveying
In plane surveying, we pretend the Earth is flat for small areas. We assume all directions of gravity are parallel and all angles are “flat” angles on a plane.
Simple Explanation: If you’re mapping a small field or neighborhood, the Earth looks almost flat—so you can use simpler math.
- Accurate enough for areas where curvature errors are tiny (e.g., 5 mi line differs by only 0.02 ft).
- Uses algebra, plane geometry, and plane trigonometry for calculations.
- Even large areas can use map projections to turn the curve into a flat map.
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