Once the closing error is known and found acceptable, it has to be distributed — spread across the traverse so that the survey closes perfectly and can be plotted. Five methods exist, and choosing between them comes down to one question: which did you measure more precisely, the angles or the distances? Why Adjustment Is Done If the…
Run a closed traverse right around a field and back to where you started, and the calculation should bring you exactly home. It never quite does. The small gap between where the computation says you finished and where you actually began is the error of closure. That gap is the single most useful number in traverse…
A traverse gives you lengths and bearings. But to plot the survey, or to compute areas, or to check that the traverse closes, you need coordinates — and there are two kinds, measured from two different origins. Getting the distinction clear is essential, because almost every traverse computation depends on converting one into the other. Latitude and…
There are five ways to record direction as you run a traverse, and they differ in one crucial respect — how often you rely on the magnetic needle. That single question determines the accuracy of each method, because a compass needle is far less precise than a theodolite. This post covers all five, in ascending order…
A traverse is the workhorse of modern surveying. Rather than building a rigid network of triangles across a landscape, you simply walk from station to station, measuring how far you went and which way you turned. This post covers what a traverse is, why it displaced triangulation, and a formula that answers a question surveyors…
A theodolite reads to 20 seconds, or with a good optical instrument to one second. But an instrument’s stated precision means nothing if the reading itself is wrong for some other reason. Errors in theodolite work fall into three categories, and knowing which category an error belongs to tells you how — or whether — it…
A vernier theodolite reads to 20 seconds. So how do you measure an angle more precisely than 20 seconds with an instrument that cannot read finer than that? The repetition method answers exactly that question, and it does so with a trick that is genuinely clever. This post covers both methods of measuring horizontal angles, and the measurement…
Before a theodolite can read a single angle, it has to be put in the right place and made ready. That preparation is done afresh every time the instrument is set down, which is why these are called temporary adjustments. This post covers all five, in the order they must be performed, and explains the practical points that…
Theodolite work has a vocabulary of its own, and much of it sounds interchangeable until you look closely. Transiting and swinging are different motions. Face left and telescope normal are related but not identical. Lining in and balancing in differ by a single condition. This post works through every definition, with the distinctions made explicit. 1. Centering The process of setting up the instrument exactly over the station…
A theodolite looks complicated because it does two independent things at once — it must turn horizontally to measure horizontal angles and vertically to measure vertical angles, while staying rigidly centred over a point on the ground. Nearly every part exists to serve one of those three requirements. This post covers the components and, more usefully, the logic that…
