A site survey before construction measures what is on and around your plot so the design fits reality: boundary beacons, ground levels and slopes, existing buildings, trees, roads, drains and utilities, and often the soil. Surveyors use total stations for precise angles and distances, GNSS (GPS) receivers for positions and levels over larger areas, and drones for fast aerial mapping. The result is a topographic survey drawing that architects and engineers design from. Skipping it, or relying on an old sketch, is how buildings end up on the wrong level, across a building line, or with drains that run uphill.
What does a site survey measure?
- Boundaries and beacons: confirming the plot matches the title deed and survey plan. See checking a land title.
- Topography: ground levels across the site, slopes and contours.
- Existing features: buildings, walls, trees, rocks, roads, drains and watercourses.
- Services: water pipes, power lines, sewers and telecom cables on or near the site.
- Access: road levels and where vehicles can enter.
- Neighbouring buildings: heights and distances that affect design and permits.
Types of survey
| Survey | Purpose |
|---|---|
| Cadastral (boundary) survey | Defines legal boundaries and beacons |
| Topographic survey | Ground levels and features for design |
| Setting out survey | Marks building positions on site before construction. See setting out |
| Engineering or road survey | Alignments, profiles and cross sections for roads and drains |
| As-built survey | Records what was actually built |
| Geotechnical investigation | Soil properties and bearing capacity. See soil testing |
Boundary surveys must be done by licensed land surveyors and registered with the land authorities.
Total stations
A total station measures horizontal and vertical angles and distances to a prism with high accuracy. It is the standard tool for:
- Topographic surveys of building sites.
- Setting out columns, foundations and gridlines.
- Checking levels and alignment during construction.
- Road and drainage works.
It needs a clear line of sight between the instrument and the prism, so dense vegetation or buildings slow it down.
GNSS (GPS) receivers
Survey-grade GNSS receivers use satellite signals, often with a base station or correction service (RTK), to fix positions and levels to within a few centimetres. They are fast in open areas and ideal for:
- Large sites and road corridors.
- Linking a site to national coordinates.
- Locating beacons.
They work poorly under heavy tree cover or between tall buildings, where a total station takes over.
Drones
Drones fitted with cameras or LiDAR capture aerial images that software turns into maps, 3D models and ground surfaces. They are useful for:
- Fast topographic mapping of large or rough sites.
- Earthwork volumes for cut and fill.
- Monthly progress photos on large projects. See monitoring construction progress.
- Inspecting roofs and tall structures safely.
Drone surveys still need ground control points measured with GNSS or total stations for accuracy. In Tanzania, flying drones requires permission from the Tanzania Civil Aviation Authority and other relevant authorities, so build that into the programme.
How the survey feeds the design
The topographic survey sets:
- The floor level of the building, above flood level and drainage outfalls.
- Cut and fill volumes, and the need for retaining walls on sloping plots.
- Driveway and road gradients. See driveways and access roads.
- Drainage falls and where water can leave the site. See stormwater drainage.
- Building position relative to building lines and setbacks.
What to ask a surveyor for
- A drawing in a format your architect can use (usually DWG), plus PDF.
- Levels tied to a known benchmark or national datum.
- Contours at a suitable interval for the site.
- All beacons shown with coordinates.
- Existing services and features clearly marked.
- A short report on the method and accuracy.
Problems a good survey reveals early
Surveys regularly turn up things that change the design:
- Beacons in the wrong place or missing, so the plot is smaller or a different shape than the owner thought.
- A bigger slope than expected, needing retaining walls or a split-level design.
- A low point where water collects, which must be drained or avoided.
- Power lines or pipes crossing the plot, with way-leaves where you cannot build.
- Neighbouring buildings over the boundary, which need resolving before construction.
- Road levels higher than the plot, so stormwater from the road runs onto the site.
Each of these is cheap to deal with on paper and expensive once foundations are in. See setting out a house and flood-proofing a building.
Time and cost
A topographic survey of a typical urban plot is a modest cost, usually a small fraction of the design fees. Large sites, rough terrain and road corridors cost more, and drones can reduce field time on big areas. Ask for a quote based on the site area, the level of detail and the deliverables listed above.
Frequently asked questions
Do I need a topographic survey for a small plot?
For a flat plot with a simple building, a basic level survey may be enough. For sloping plots, larger buildings or drainage concerns, a full topographic survey is worth it.
Who can do a boundary survey in Tanzania?
A licensed land surveyor. Boundary changes and new beacons must go through the land authorities.
Are drone surveys accurate?
With proper ground control, drone surveys can reach a few centimetres in open terrain, enough for earthworks and planning. Precise setting out still uses total stations.
How long does a site survey take?
A small building plot may take a day or two in the field, plus processing. Large sites and road corridors take longer.
What is a benchmark in surveying?
A point with a known, fixed level that all other levels on the site are measured from. It should be protected and not disturbed during construction.
Do I need a new survey if I already have the title plan?
Usually yes. The title plan shows boundaries, not ground levels, trees, drains or services, which the designers need.
Can a drone replace a land surveyor?
No. A drone is a tool. A qualified surveyor plans the flight, sets ground control, checks accuracy and signs the results.
Need surveying and setting out?
Vika Construction's engineers set out and check every project with modern instruments. See our civil and infrastructure work or contact us.
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