Of all the instruments in surveying, the theodolite is the one that measures angles precisely. A compass gives you a rough direction; a theodolite gives you an angle to within seconds of arc. This post covers what a theodolite does, the two ways it is classified, and how its size is specified. What a Theodolite Is…
Every survey line has two ends, and you can stand at either one and take a bearing. The two readings will not be the same number — but they describe the same line, and the relationship between them is fixed and simple. That relationship turns out to be one of the most useful checks in…
The same direction can be written down in two completely different ways. “One hundred and thirty five degrees” and “South 45 degrees East” describe the identical line — they are just two conventions for saying the same thing. This post covers both systems, and the conversion between them that examinations test constantly. The Two Systems…
Here is a fact that surprises students the first time they meet it. A single survey line, running in one fixed direction across the ground, can be correctly described by four different numerical bearings — all of them right at the same time. Nothing about the line has changed. What differs is the meridian each bearing is…
A bearing is measured from a meridian — but which meridian? Four different reference directions are used in surveying, and each produces a different bearing for the very same line. This post covers all four, explains when each is used, and introduces the compass traverse. Why More Than One Meridian Exists Recall the definition: a meridian is any…
Chain surveying can only measure distances, and that limitation is what forces it into small open sites. To survey anything larger you need the second half of the information — direction. This post covers why direction matters, the systems used to measure angles, and the two ideas that underpin the whole of compass surveying: the meridian and the bearing….
In precise taping, a raw measurement is never the answer. The tape may be the wrong length, held at the wrong tension, at the wrong temperature, sagging between supports, off the line, on a slope, or high above sea level — and each of those changes the reading. This post covers all seven corrections, their formulas,…
Systematic errors have identifiable causes, which means they can be calculated and removed. This post covers the sign convention that governs all corrections, and the two corrections applied to ordinary chain measurements — standardization and slope. The Sign Convention Everything in this topic depends on getting the signs right, so start here. 1. Error = Measured distance −…
No measurement is perfect. What matters in surveying is not whether errors occur — they always do — but whether they cancel out or pile up. That single distinction divides all chaining errors into two classes, and it decides how seriously each one has to be treated. Where Chaining Errors Come From Errors and mistakes in…
A tape is 30 metres long. The line you need to measure is 300 metres. So you lay the tape down ten times — and unless every one of those ten positions lies exactly on the straight line between the two ends, you have measured a zigzag instead of a distance. Ranging is the process of…
