Survey Drawings, Maps and Field Records
Survey Drawings, Maps and Field Records
This domain tests whether field measurements become a legible, checkable map: scale, plotting, symbols, north direction, legends and the field book. Expect scale conversions and identification of recording errors.
Core rules
- Scale is expressed as a representative fraction (RF), such as 1:2500, or as a graphical scale. RF is unitless: 1 cm on the map represents 2500 cm = 25 m on the ground.
- To convert a map distance to ground: ground distance = map distance × denominator of RF. To convert ground to map: map distance = ground distance / denominator.
- A survey plan needs a title, scale, north arrow, legend, boundary, plot numbers and reference to the field book. A contour plan also needs the contour interval.
- The chain survey field book records station, chainage, offset length and side (left or right), plus remarks. Offsets are plotted perpendicular to the chain line at the recorded chainage.
- Shrinkage of drawing paper changes a graphical scale but not the RF written on the sheet; check a graphical scale against its original length.
Worked example
A plan has RF 1:2500. A plot measures 4.0 cm by 3.0 cm on the map. Ground sides: 4.0 × 2500 cm = 10,000 cm = 100 m; 3.0 × 2500 cm = 7500 cm = 75 m. Ground area = 100 × 75 = 7500 m² = 0.75 ha. The map area is 12 cm²; the area scale factor is 2500², so 12 cm² × 6,250,000 = 75,000,000 cm² = 7500 m².
Traps
Do not write 1 cm = 2500 m for RF 1:2500; it is 25 m. Do not omit the north arrow or legend. Do not record an offset without its side; a right offset plotted on the left reverses the shape. Do not confuse map area with ground area by forgetting to square the scale factor.