Road and Bridge Surveying
Comprehensive surveying for road and bridge projects. El-Eman Office provides route surveying services across Egypt.
From alignment to construction: stages of road surveying
In road and bridge surveying, work passes through successive stages. It starts with reconnaissance and choosing a preliminary route, then a topographic survey over a corridor wide enough to allow for adjustments, followed by design of the horizontal alignment and the longitudinal profile. Once the design is approved, the centreline is set out with points at regular intervals, the land acquisition boundary is defined, and layer levels are transferred one after another. Work ends with an as-built survey and checking that it conforms to the design.
Road elements fixed by survey
- Horizontal curves: the start and end positions and the radius, set out with intermediate points.
- Vertical curves: which join two different grades for visibility and comfort.
- Cross fall and superelevation: for drainage and better stability on curves.
- Layer levels: excavation bottom, improved subgrade, base and paving.
- Drainage works: levels of culverts, drains and side ditches.
The special nature of bridge surveying
Bridges demand higher accuracy because any deviation in the supports accumulates over the spans. Each pier is set out by its coordinates, then the positions of piles, pile caps and columns are checked. Verticality and squareness are monitored while columns are built, and the levels of pier tops are measured precisely to position precast beams or girders. The effect of temperature on long members must be considered when measuring, and survey work coordinated with construction to choose suitable measurement times.
Mistakes that reduce work quality
- Relying on too few control points that do not form a closed network.
- Failing to update the survey when site conditions change after a long time.
- Not checking each layer's levels before covering it with the next layer.
- Confusing the road centreline with its edge during setting-out.
- No documentation of the quantities actually executed.
Quality control in road layers
A road is made of layers built in sequence, each with a specified level, thickness and slope. The surveyor checks each layer after compaction and before covering it, measuring levels at points on the centreline and edges according to a defined grid. Any layer outside the permitted tolerance is corrected, because its error passes to the layers above and affects asphalt thickness and water drainage.
- Levels are measured after compaction, not before.
- Results for each layer are recorded to prove conformity.
- Cross fall on curves is checked with particular care.
Frequently asked questions
Why are cross-sections taken at intervals?
Because they represent the natural and design ground for volume calculation, and the spacing is reduced where terrain or curves change quickly.
What is the use of an as-built survey on roads?
It documents what was actually built, proves conformity with the design, and is used in handover, maintenance and planning future widening.
Is GPS alone enough for road projects?
It helps on long routes and for control, but accurate setting-out and layer levels need a total station and a level, combining instruments according to the stage.
