Route surveys for pipelines, roads and cables: from desk study to setting out
Geomarins Integrated Limited ·
How route surveys are carried out for pipelines, roads, power lines and cables in Nigeria: desk study, corridor survey, crossings, right of way and setting out.
A pipeline, road, power line or cable is a long, narrow project. Its route decides much of the cost, the construction difficulty, the land to be acquired and the approvals needed. A good route survey finds the best line early and gives designers and contractors accurate information all the way along it.
Desk study
Route work starts in the office. Maps, satellite imagery, existing surveys and records are used to find possible routes and to identify constraints: settlements, rivers, swamps, protected areas, existing pipelines and roads. Each option is compared for length, crossings, ground conditions and land issues.
Reconnaissance
A field visit checks the options on the ground. Things that cannot be seen on imagery, such as new buildings, soft ground, access tracks and local concerns, are recorded. The visit often narrows the choice to one preferred route.
Corridor survey
Along the preferred route, a strip of land is surveyed in detail. The survey records ground levels, features, buildings, trees, watercourses and existing services. GNSS ties the survey to national control, while total stations and levelling capture detail. The result is a ground model and drawings the designers can work from.
Crossings
Crossings are where routes get complicated. Each road, railway, river, creek or existing pipeline crossing is surveyed in detail: levels, widths, banks and services. In the Niger Delta and coastal areas, routes cross swamp, mangrove and tidal channels, where access and methods are planned around tides and ground conditions. Where a route reaches the coast, waves, currents and water levels at the landfall also need to be measured.
Right of way
The route passes through land with many owners and users. The survey records the right of way boundaries, the parcels crossed and the features within them. This information supports land acquisition and fair compensation.
Alignment and setting out
Once the design is fixed, the centreline, bends and key points are set out on the ground with pegs or markers, so construction follows the design. During construction, the surveyors check positions and levels.
As-built survey
When the work is complete, an as-built survey records exactly where the pipeline, cable or road was placed. That record is essential for operations, maintenance and for anyone who later needs to dig nearby.