Chain surveying is the oldest and simplest branch of the subject, and for a long time it was so dominant that surveying itself was often called chain surveying. This post covers what it is, why the equipment changed, where it works well, and the four categories of detail a survey has to record.
Why It Is Called Chain Surveying
Surveying is often referred to as chain surveying, or tape and offset surveying, if the principal item of equipment traditionally used is a measuring chain or tape.
Note the alternative name — tape and offset surveying — because it describes the method more accurately than “chain surveying” does. The work consists of measuring along survey lines with a tape, and then measuring short offsets sideways from those lines to pick up the features on either side.
From Chain to Steel Band
Nowadays, as a result of improvements in manufacturing techniques and a consequential reduction in purchase price, the chain has been replaced by the more accurate steel band.
Two reasons are given, and both matter.
A surveyor’s chain is made of many linked pieces. Every link is a joint, every joint wears, and wear makes the chain stretch over time. A steel band is a single continuous strip with no joints at all, so it holds its length far better.
The chain survived as long as it did because bands were expensive to make accurately. Once manufacturing improved and prices fell, there was no longer any reason to accept the chain’s inaccuracy — so it was replaced.
Where Chain Surveying Suits
| Suitable For | Not Suitable For |
|---|---|
| Areas of small extent | Large areas |
| Open ground | Obstructed ground |
| Few simple details | Many details |
The reasons follow from the method’s one great limitation — chain surveying takes no angular measurements at all. Every position must be fixed by measuring lengths alone.
That works well when the area is small and open, because you can run straight lines across it and measure short offsets to a handful of features. It breaks down when the area is large (errors accumulate with no angular check), when the ground is obstructed (lines cannot be run straight), or when there are many details (each one needs its own offset, and the work becomes endless).
What “Detail” Means
In surveying, the term detail means a natural or man-made feature at or near the ground surface.
Detail is what the survey is actually recording. The survey lines themselves are only a framework; the detail is the information the client wants.
The Four Types of Detail
| Type | Examples |
|---|---|
| 1. Hard details | Buildings, roads, walls |
| 2. Soft details | Vegetation, trees, rivers |
| 3. Overhead details | Power and telephone lines |
| 4. Underground details | Water mains, sewers |
Why the Categories Differ in Practice
These four are not just a list — each presents a different surveying problem.
Hard details are the easiest. A wall or a building corner is solid, permanent and has a definite edge you can measure to. Ask two surveyors to locate the same building corner and they will agree.
Soft details are harder, because they have no definite boundary. Where exactly does a patch of vegetation end? Where is the edge of a river — at low water or high? These features also move and grow between surveys.
Overhead details cannot be measured directly at all, because they are in the air. What gets recorded is the position of the poles or towers, and the line between them.
Underground details are the most difficult, because they are invisible. A sewer or water main cannot be seen or reached. Their positions come from manhole covers, from records held by the utility, or from detection instruments — never from direct measurement of the pipe itself.
Why Underground Detail Matters Most
Of the four, underground detail causes the most trouble on real projects. A building shown in the wrong place on a plan is an inconvenience. A sewer or a buried cable shown in the wrong place is discovered by an excavator, and the consequences are expensive and sometimes dangerous.
How This Fits the Rest of the Chapter
The topics that follow are all consequences of the method described here:
- Measuring with a tape means you need to know about types of tape and their behaviour.
- Running long straight lines means you need accessories and ranging.
- Measuring with a physical tape means errors creep in, which leads to corrections.
- Chain surveying’s inability to measure angles is precisely what leads on to compass surveying and bearings.
Quick Revision Notes
- Surveying is often called chain surveying or tape and offset surveying when the main equipment is a measuring chain or tape.
- The chain has been replaced by the more accurate steel band, thanks to improved manufacturing and reduced price.
- Chain surveying suits small areas of open ground with few simple details.
- It is not suitable for large areas having many details.
- Detail = a natural or man-made feature at or near the ground surface.
- Four types of detail: hard (buildings, roads, walls), soft (vegetation, trees, river), overhead (power and telephone lines), underground (water mains, sewers).
Mistakes Students Commonly Make
- Listing only two or three types of detail. There are four, and underground detail is the one most often forgotten.
- Putting a river under hard details. A river is a soft detail.
- Saying the chain was replaced because it was slow. It was replaced because the steel band is more accurate, and became affordable.
- Forgetting the alternative name tape and offset surveying.
- Claiming chain surveying suits any small area. It needs open ground with few simple details.
Conclusion
Chain surveying measures distances and nothing else, which makes it simple, cheap and entirely adequate for a small open site with a few features to record. Its equipment has improved — the jointed chain giving way to the more accurate steel band — but its limitation has not changed. With no angular measurement available, it cannot cope with large areas or crowded detail, and that limitation is exactly what the rest of this chapter sets out to overcome.
Frequently Asked Questions
Why is surveying often called chain surveying?
Because the principal item of equipment traditionally used is a measuring chain or tape. It is also known as tape and offset surveying.
Why has the chain been replaced by the steel band?
Because improvements in manufacturing techniques and the resulting reduction in purchase price made the more accurate steel band the better choice.
Where is chain surveying suitable?
For areas of small extent on open ground having few simple details. It is not suitable for large areas with many details.
What does detail mean in surveying?
A natural or man-made feature at or near the ground surface.
What are the four types of detail?
Hard details such as buildings, roads and walls; soft details such as vegetation, trees and rivers; overhead details such as power and telephone lines; and underground details such as water mains and sewers.
Why are soft details harder to survey than hard details?
Because they have no definite boundary. The edge of vegetation or the bank of a river is not a sharp line, and such features also change between surveys.
Why are underground details the most difficult?
Because they cannot be seen or measured directly. Their positions must be inferred from manhole covers, utility records or detection instruments.