What is surveying?
Surveying is measuring the positions of points on or near the earth: how far apart they are, in which direction, and how high. The results are drawn as a plan (small area, much detail) or a map (large area, less detail).
The person who does it is a surveyor. He uses tape, level, theodolite, total station and GPS.
The three things a surveyor measures
- Distance between two points (in metres).
- Angle or direction between lines (in degrees).
- Height (elevation) of a point above a chosen level, often mean sea level.
With these three, any point on the land can be placed on paper.
Why surveying matters: its role
- Planning: where to place a road, canal, railway or pipeline.
- Construction: building corners, levels and slopes are marked from survey.
- Land records: boundaries and area of plots; fewer disputes.
- Maps: every map starts from some survey.
- Safety and environment: flood levels, land slope, forest area.
Plan, map and scale
The scale is the ratio of a length on the map to the same length on the ground. A scale of 1 : 1000 means 1 cm on the map is 1000 cm (10 m) on the ground. A bigger bottom number means a smaller drawing with less detail.
Ground distance = map distance x scale number. Map distance = ground distance / scale number.
Key formulas and definitions
- Scale 1 : N means 1 unit on map = N units on ground
- Ground distance = map distance x N
- Map distance = ground distance / N
- 100 cm = 1 m
Worked examples
1. On a map of scale 1 : 1000, two trees are 4 cm apart. What is the real distance?
Ground = 4 x 1000 = 4000 cm = 40 m.
2. A school ground is 80 m long. How long is it on a plan of scale 1 : 500?
80 m = 8000 cm. Map = 8000 / 500 = 16 cm.
3. On a plan of scale 1 : 200, a room is 3.5 cm wide. Find the real width.
3.5 x 200 = 700 cm = 7 m.
4. Which plan shows more detail, 1 : 500 or 1 : 5000?
1 : 500. A smaller number under the 1 means the ground is shrunk less, so more detail fits.
Common mistakes
- Mixing units: map in cm but ground in m. Convert first.
- Thinking a bigger scale number means a bigger map. It means a smaller map.
- Thinking a map and a plan are the same size. A plan covers a small area in detail.
- Believing surveying is only for engineers.