How to Read an SG Diagram: Beacons, Dimensions & Boundaries

An SG (Surveyor General) diagram is the official survey of a single piece of land. It pins down where your boundaries run, where the corner beacons sit, how long each boundary line is, the total size of the property and whether any servitudes cross it. It is the cadastral picture of the land itself, not a record of who owns it. Once you know what each marking means, a diagram that first looks like a tangle of figures and codes becomes surprisingly readable. This guide walks a non-surveyor through it, piece by piece.

Start with the figure: the shape of the land

The large drawn shape in the centre of the diagram is the figure of your property: an outline of the actual land parcel, drawn to scale. Most erven are simple four-sided figures, but they can be irregular, five-sided, curved along a road, or oddly notched. Match the shape on paper to the shape you see on the ground or on an aerial map. If a boundary is curved, you will usually see a radius and an arc length noted along it rather than a single straight measurement.

Beacons: the labelled corners

Each corner of the figure is a beacon, the surveyed point that physically marks where the boundary turns. On the ground these are pegs, iron beacons or concrete marks. On the diagram each beacon is given a label, usually a letter or a letter-and-number such as A, B, C or A1, B1. These labels matter because every boundary line is described by the two beacons it runs between.

• Letters or numbers at each corner identify the beacons in sequence.
• A small symbol or note may indicate the type of beacon placed, for example a standard iron peg.
• If a beacon is shared with a neighbouring property, the same point appears on both diagrams.

Boundary lengths and bearings

Running along each side of the figure you will find two numbers: the length and the bearing of that boundary line. The length is the distance between the two beacons, given in metres. The bearing is the direction the line points, written in degrees, minutes and seconds (for example 142° 30' 15"), measured clockwise from a reference meridian, not from magnetic north. Together they fix each boundary precisely. You do not need to do the trigonometry yourself; just know that one number is how long the side is and the other is which way it heads.

The extent: how big the property is

Somewhere on the diagram, often near the title block, is the extent, the total area of the property. Urban erven are usually expressed in square metres (m²). Rural land, such as farms and agricultural holdings, is usually expressed in hectares (ha). This figure is the surveyed size of the parcel and the authoritative answer to how big the property is. If the land has been subdivided over the years, the extent on the current diagram reflects the portion you actually hold.

Servitude strips

A servitude is a right that someone else holds over part of your land, such as a municipal pipeline, a power line, or a right of way for a neighbour. On the diagram these appear as strips or hatched areas crossing the figure, often with their own width and position noted. They tell you that, although the land is yours, a defined strip carries an obligation or restriction. Spotting a servitude on the diagram is one of the most practical reasons to read it before building, fencing or planning anything near a boundary.

Scale, the SG number and the surveyor

A few smaller details anchor the whole document:

• Scale tells you the ratio between the drawing and reality, such as 1:500, so the figure fits on a page while every measurement stays accurate.
• The SG number (diagram number) is the unique reference for the diagram itself. It is distinct from the erf number and from the title deed number.
• The surveyor's details, usually in the title block, name the professional land surveyor who carried out the survey and the date it was approved, which is what gives the diagram its official standing.

What the diagram does not tell you

An SG diagram is silent on ownership. It will not name the owner, list the bond, or show the chain of transfers. That information lives in the title deed, a separate document held at a different office. If your question is "who owns this?" or "is there a bond over it?", the diagram is the wrong document and you should turn to the deeds record instead, which you can look up through DeedsCheck. Keep the two apart: the diagram is the survey, the deed is the ownership.

Getting your hands on the diagram

You cannot read an SG diagram until you have it in front of you. To see which diagrams exist for a property and pull the actual PDF, run a free search on SGCheck by address on the map, or by erf number, town and portion. The free search shows you what is on file at no cost; from there a single R230 fee lets you retrieve and download every diagram on the property as a PDF. Sectional title properties, such as flats and townhouses, are sourced manually on request rather than instantly. Once the diagram is open, this guide should help you make sense of every line and label on it.

Frequently asked questions

Is the SG number the same as my erf number?

No. The erf number identifies the property within its township, while the SG number (diagram number) is the unique filing reference for the survey diagram itself. A single property can also have more than one diagram on file if it has been surveyed or subdivided over time.

Why are the bearings not measured from north?

Bearings on an SG diagram are measured clockwise from a fixed survey reference meridian rather than from magnetic north, because magnetic north drifts over time. Using a fixed reference keeps the directions consistent and accurate for as long as the diagram exists, which is why they are written precisely in degrees, minutes and seconds.

How do I work out the property's exact size from the diagram?

Look for the extent, usually near the title block. It is the surveyed total area, given in square metres for urban erven and in hectares for farms and agricultural holdings. This is the authoritative size of your parcel, not an estimate read off the drawing.

Does the SG diagram show who owns the property?

No. The SG diagram is the survey of the land and contains no ownership, bond or transfer information. Those details are in the title deed, a separate document, which you can look up through DeedsCheck rather than from the diagram.