Every survey is carried out for a reason, and the reason determines almost everything about it — what gets measured, how accurately, and at what scale. This post covers the six types of survey classified by purpose, together with the scales that go with them.
The Six Types
- Topographical survey
- Engineering survey
- Cadastral survey
- Hydrographic survey
- Astronomic survey
- Geological survey
1. Topographical Survey
A survey conducted to obtain data and make a map indicating inequalities of the land surface, by measuring elevations and locating the natural and artificial features of the earth — for example rivers, woods and hills.
Scale range: 1 : 25,000 to 1 : 1,000,000
Note the two halves of the definition. A topographical survey records height (“inequalities of the land surface”, measured by elevations) and features (both natural and artificial). It is a general-purpose picture of the ground.
The scales are small — 1:25,000 at the largest — which fits the earlier point that a map is a small scale representation covering a large area.
2. Engineering Survey
These are the survey works required before, during and after any engineering works.
What Engineering Surveys Provide
- Before work starts, large-scale topographical maps or plans are required as a basis for design.
- Especially used for the design and construction of new routes, such as roads and railways.
- Used to calculate areas and volumes of land.
- Used to obtain data for setting out curves for route alignment.
The “Before, During and After” Point
This phrase is worth noticing, because engineering surveying is not a one-off activity.
- Before: mapping the site so the design can be prepared.
- During: setting out — transferring the design onto the ground so contractors build in the right place.
- After: measuring what was actually built, for payment, records and checking.
The reference to setting out curves for route alignment connects directly to highway engineering — the horizontal and transition curves designed there have to be physically pegged out on site, and that is a surveying job.
3. Cadastral Survey
Undertaken to produce plans of property boundaries for legal purposes. Also known as public land survey.
Scale range: 1 : 1,000 to 1 : 5,000
This is the only survey type on the list whose purpose is legal rather than physical. Nobody is designing or building anything — the object is to establish who owns what, and where the boundary between two properties lies.
That legal character explains the larger scale. Property disputes turn on metres, sometimes centimetres, so cadastral plans need more detail than topographical maps.
4. Hydrographic Survey
Conducted on or near a water body — lakes, rivers, bays, harbours.
What a Hydrographic Survey Determines
- Locating shore lines
- Water flow estimation
- Determination of the shape of the area under the water surface
- Determination of channel depth
- Location of locks, sand bars, buoys, and similar features
Marine Surveys
Marine surveys are a special type of hydrographic survey, covering a broader area near the sea for offshore structures, navigation, tides and similar purposes.
The distinguishing feature of hydrographic surveying is that much of what must be measured cannot be seen. The shape of the bed, the depth of the channel, the position of a sand bar — all lie beneath the water surface, which is why this branch developed its own techniques.
5. Astronomic Survey
Conducted for the determination of latitudes, azimuths and local time at various places on the earth, by observing heavenly bodies — the sun or stars.
This is the one survey that looks upward. Every other type measures from point to point on the ground; astronomic surveying takes its reference from the sky.
Why does that matter? Because ground measurements are always relative — they tell you where B is with respect to A, but not where A is on the earth. Observations of the sun and stars fix absolute position and direction, giving the whole network something external to hang from.
6. Geological Survey
Conducted to obtain information about the different strata of the earth’s surface for the purpose of geological studies. Geological maps are prepared depicting the details of the strata.
Like hydrographic surveying, this branch is concerned with what lies out of sight — but downward rather than under water. The subject is the arrangement of rock layers beneath the surface.
All Six Compared
| Survey | Purpose | Scale |
|---|---|---|
| Topographical | Map land surface inequalities, natural and artificial features | 1:25,000 to 1:1,000,000 |
| Engineering | Support design, construction and measurement of works | Large scale plans |
| Cadastral | Property boundaries for legal purposes | 1:1,000 to 1:5,000 |
| Hydrographic | Water bodies, shore lines, depths, underwater shape | — |
| Astronomic | Latitude, azimuth and local time from heavenly bodies | — |
| Geological | Strata of the earth for geological study | — |
A Way to Group Them
The six sort naturally by where they look:
- On the ground: topographical, engineering, cadastral
- Under water: hydrographic, and marine as its special case
- Under the ground: geological
- Above the ground: astronomic
Comparing the Two Stated Scale Ranges
Only two of the six carry stated scales, and comparing them is instructive:
| Cadastral | Topographical | |
|---|---|---|
| Scale | 1:1,000 to 1:5,000 | 1:25,000 to 1:1,000,000 |
| Scale type | Larger | Smaller |
| Area covered | Smaller | Larger |
| Detail | More | Less |
Remember from the introduction that a smaller denominator means a larger scale. So 1:1,000 is a larger scale than 1:25,000, and cadastral plans accordingly show far more detail over far less ground — exactly what legal boundary work requires.
Quick Revision Notes
- Six types by purpose: topographical, engineering, cadastral, hydrographic, astronomic, geological.
- Topographical: maps inequalities of land surface by measuring elevations and locating natural and artificial features; scale 1:25,000 to 1:1,000,000.
- Engineering: required before, during and after engineering works; used for route design, area and volume calculation, and setting out curves.
- Cadastral: property boundaries for legal purposes; also called public land survey; scale 1:1,000 to 1:5,000.
- Hydrographic: on or near water bodies; locates shore lines, estimates water flow, determines underwater shape and channel depth, locates locks, sand bars and buoys.
- Marine surveys are a special type of hydrographic survey covering broader sea areas for offshore structures, navigation and tides.
- Astronomic: determines latitudes, azimuths and local time by observing the sun or stars.
- Geological: obtains information about earth strata; geological maps depict the strata.
Mistakes Students Commonly Make
- Forgetting that cadastral surveys are also called public land surveys.
- Swapping the two scale ranges. Cadastral is 1:1,000 to 1:5,000; topographical is 1:25,000 to 1:1,000,000.
- Treating marine survey as a seventh type. It is a special type of hydrographic survey.
- Saying topographical surveys record only heights. They record both elevations and features, natural and artificial.
- Limiting engineering surveys to the design stage. They are needed before, during and after the works.
- Confusing astronomic survey with geological survey. One observes heavenly bodies; the other studies earth strata.
- Assuming 1:25,000 is a larger scale than 1:1,000. The smaller the denominator, the larger the scale.
Conclusion
Purpose decides everything about a survey. Topographical surveys map the shape and features of the land at small scale; engineering surveys serve a project from design through construction to measurement; cadastral surveys settle legal boundaries at large scale; hydrographic surveys reveal what lies beneath water; astronomic surveys fix absolute position from the sky; and geological surveys describe the strata below. Learn each definition with its scale where given, and note the grouping — three look at the ground, one below water, one below ground, and one above.
Frequently Asked Questions
What are the six types of survey based on purpose?
Topographical, engineering, cadastral, hydrographic, astronomic and geological surveys.
What is a topographical survey?
A survey conducted to obtain data and make a map indicating inequalities of the land surface, by measuring elevations and locating natural and artificial features such as rivers, woods and hills.
What scales are used for topographical surveys?
From 1:25,000 to 1:1,000,000.
What is a cadastral survey?
A survey undertaken to produce plans of property boundaries for legal purposes. It is also known as a public land survey, and uses scales from 1:1,000 to 1:5,000.
What is an engineering survey?
Survey work required before, during and after engineering works — providing maps for design, especially of new roads and railways, calculating areas and volumes, and giving data for setting out curves for route alignment.
What is a hydrographic survey?
A survey conducted on or near a water body such as a lake, river, bay or harbour, involving location of shore lines, estimation of water flow, determination of the underwater shape and channel depth, and location of locks, sand bars and buoys.
What is a marine survey?
A special type of hydrographic survey covering a broader area near the sea, for offshore structures, navigation and tides.
What is an astronomic survey?
A survey conducted to determine latitudes, azimuths and local time at various places on the earth by observing heavenly bodies such as the sun or stars.
What is a geological survey?
A survey conducted to obtain information about the different strata of the earth’s surface for geological studies, resulting in geological maps depicting the details of the strata.
Which survey type uses the largest scale?
Of the two with stated ranges, cadastral surveys at 1:1,000 to 1:5,000 use a larger scale than topographical surveys, because legal boundary work requires greater detail.