Points to consider when establishing traverse

While selecting and establishing the stations of a theodolite traverse in the field, the following should be considered.

1. Intervisibility: each station must be visible from the preceding and the following stations, with a clear line of sight above the ground (at least about 1 m clear).
2. Firm and stable ground: so that the instrument does not settle, and the station is not disturbed by traffic, water or construction.
3. Length and number of sides: as few stations as possible, with long, nearly equal sides (typically 100 to 300 m); avoid very short sides, because centring errors then cause large angular errors.
4. Closeness to the details: stations should allow the details to be taken by short offsets or radiation.
5. Shape of the traverse: avoid very sharp angles and grazing lines near obstructions, which cause refraction errors.
6. Accessibility and safety: easy to reach, safe for the instrument and operator, and out of the sun and glare as far as possible.
7. Permanence and referencing: mark by pegs, nails or concrete pillars; reference to nearby permanent objects with sketches and tie distances.
8. Ties to existing control: at least start and end on known stations or reference lines for orientation.
9. Free from disturbances: avoid power lines (for compass work) and heat shimmer over roads and rooftops.