Question 2 of 5: Does a Cadastral Boundary Have a Width?

Question 2: Does a Cadastral Boundary Have a Width? (25%)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

This is a deliberately two-sided question, and the honest answer is that a cadastral boundary has no width in law but unavoidably has some width in practice. Both propositions are defensible, and a good cadastral surveyor holds them together: the boundary is a legal abstraction of zero width, realised on the ground only through physical evidence that is itself imperfect. I argue each position in turn.

The case that a boundary does NOT have a width — the legal abstraction. In law a boundary is a line, and a mathematical line has length but no breadth. It is the immaterial limit that separates one estate from the adjoining one; it is defined by its termini (the corners) and the geometry of the calls between them, not by any physical object. Ownership on one side stops and ownership on the other side begins at that line, with no strip of "boundary land" belonging to neither or to both. This is why title plans and legal descriptions speak of a line running "from monument A to monument B," never of a boundary two centimetres wide. The zero-width abstraction is essential: it is what allows areas to be computed unambiguously, adjoining parcels to abut with no gap or overlap, and a single unique point to be identified as "the corner." Example: where two subdivision lots share a common boundary, the rear fence, a row of shrubs, or a painted line may sit near the boundary, but the legal limit is the theoretical line joining the two original corner monuments — an object of zero thickness. If the fence is 0.15 m to one side, the fence is simply an encroachment or a setback; it does not make the boundary 0.15 m wide. The line itself remains dimensionless.

The case that a boundary DOES have a width — the practical zone of uncertainty. The moment we try to locate that ideal line on the physical earth, width reappears, because every element used to realise it carries measurement and interpretive uncertainty. The corner monument is not a mathematical point but a bar, pipe, or post of finite diameter, possibly disturbed, whose recovered centre is known only to within the survey's positional tolerance. The measured bearings and distances that place it carry standard errors, so the surveyor can honestly say only that the corner lies within a small region (an error ellipse) at some confidence level, not at an exact coordinate. Add the interpretive latitude in weighing conflicting evidence, and the boundary in practice occupies a narrow zone of uncertainty rather than an infinitely thin line — which is exactly why some jurisdictions register "general boundaries" (deliberately approximate) and why re-surveys of the same line by different competent surveyors seldom coincide to the millimetre. Example: two surveyors independently re-establish the same lot boundary from the same registered plan; one recovers the corner at a slightly different position than the other because the original iron bar is loose in the ground and their traverses close differently. Their two "lines" are perhaps 20–40 mm apart. For all practical purposes the true boundary lies somewhere in that band — a measurable width — and disputes over fences and buildings are fought precisely within it.

Reconciliation. The two positions are not truly in conflict; they describe different things. As a legal concept the boundary is a zero-width line — that is the definition that gives title its certainty. As a physical realisation it is a zone of uncertainty whose width is set by the quality of the evidence and the survey. The cadastral surveyor's professional job is to collapse that practical width to the smallest defensible band and then report a single best-estimate line — while remembering that the reported line is an opinion about where the dimensionless legal line lies, not a claim that the boundary was ever physically thin.