Reconnaissance Survey for Routes and Sites

What is a reconnaissance survey?

A reconnaissance survey is the first, quick look at an area or a route, done from maps, imagery and a site visit. It finds feasible options and obstacles before any detailed survey is paid for. Engineers shorten it to "recce", and its output is a short report with a sketch of alternatives, not a measured drawing.

A team planning a road between two towns, a fibre route along a highway or a pipeline to a factory cannot survey every line in detail. The recce narrows the choice to one or two corridors and flags river crossings, settlements, steep ground and existing services with a rough cost. A skipped one tends to return as a redesign.

Where does a recce sit among the survey stages?

It comes first, before the preliminary survey and the final location survey. The Indian Roads Congress manual for road project surveys, IRC:SP:19, sets out this sequence. Reconnaissance to find feasible routes, a preliminary instrument survey of the chosen corridor, and a final location survey that pegs the centreline¹.

Measurement begins at the preliminary stage, with a traverse, levels, cross-sections and benchmarks; the manual suggests cross-sections every 100–250 m on plain ground and tighter in hills. Detail and contours follow at design stage. To budget that step, see how long a topographic survey takes once the corridor is fixed.

What does a desk recce look at before anyone goes out?

Maps, imagery and records come first: topographic sheets, satellite and aerial images, geology and soil maps, flood records and existing utility or land information. IRC:SP:19 lists Survey of India sheets at 1:25,000, 1:50,000 and 1:250,000 as most useful. When it was written, the two smaller scales covered the whole country and 1:25,000 about 30 per cent¹.

• Sheets and recent imagery: contours and drainage, plus new colonies and road widenings the sheets miss; drone mapping adds detail on open ground.
• Geology, soil and flood data: rock, soft clay, high flood levels and seasonal streams.
• Rights of way: highways, rail lines, pipelines, power lines and protected areas.

The desk work ends with candidate lines joining the fixed "obligatory points", such as the start, the end, a bridge site or a pass, while avoiding obvious trouble.

What does the team check on the ground?

The ground recce tests whether each line is buildable, checking crossings, slopes, soil, access, settlements and anything the maps missed. The IRC manual lists a compass, Abney level, clinometer, aneroid barometer and GPS for slopes and positions¹. Today a handheld GPS receiver is the most used. Its global positioning system fix from raw GPS signals is good only to metres, which is enough for satellite based positioning at recce stage.

• River, canal, rail and highway crossings, photographed with approximate widths.
• Gradients steeper on site than on the map, and encroachments, shrines or trees needing removal.
• Soil exposures, waterlogged patches, access roads and space for site stores.
• Visible signs of buried services, such as valve chambers, cable markers and telecom joint pits.

A few reference pegs are left and photographed, so the later crew starts in the right place.

Recce mistakes that come back later

• Old sheets alone: a colony built five years ago will not be on them.
• Dry-season visits only: a field firm in April may flood in August.
• Centreline only: working space, access and stacking areas matter as much.
• Ignoring ownership: permissions often decide the route more than engineering does.

What does a recce look like for a single site?

A site recce is shorter but has the same purpose: find what will shape the survey and design before measurement starts. On a factory plot or school campus, one morning shows whether the boundary pillars are visible and whether trees block open sky for a base station. It also shows where rainwater leaves the site, and which poles and manholes hint at buried services. Those answers fix the method, crew and days, so a fair quotation often follows a short visit or good photographs.

How is a route recce done for cables, ducts and HDD?

A route recce for cables, ducts and HDD pays extra attention to what is already buried and to where machines can enter and exit. Along an existing road, the main question is congestion, not gradient: how many cables, pipes and chambers share the verge, and where crossings must go.

For an optical fibre route the recce records road width, verge type, side drains, culverts, junctions and existing ducts, and marks stretches likely to need trenchless crossings. A detailed radar scan of the chosen line follows, as summarised in OFC route GPR survey at a glance. Where directional drilling is planned, it also checks pit space, soil and crossing depths; our note on HDD route survey covers the next stage.

Skipping the buried-services check is the usual cause of drill strikes, since one footpath can hide a water main, a gas line and three generations of cable.

What should a reconnaissance report contain?

The report holds a plan of the alternatives at 1:50,000 or larger, a short description of each, the crossings, rough quantities and costs, and a recommendation. IRC:SP:19 asks for alternative alignments with general profiles, rough estimates and a discussion of merits¹.

Recce positions are enough to choose a line, but the detailed survey needs control tied to the national frame through a reference station network. For that layer, see more on Geodetic Survey.

What does the survey after the recce cost?

Mezux Touch charges ₹12,000 per km for a route survey with centreline and cross-sections every 25 m, with a ₹50,000 minimum. A strip of levels and detail along a road or route is ₹15,000 per km, GST extra, and a written quotation sets the final amount once the corridor is known.

Utility scanning along the chosen line is charged separately at ₹24 per metre, or ₹32 per metre with an L-section drawing. Delhi NCR crews start the same day or within 1 working day. Elsewhere in India, a team member based near the corridor walks the recce immediately or within 1 working day, with any mobilisation/travel cost, if applicable, in the quotation. Cross-section intervals and drawing formats are also fixed there. With a start point, an end point and a rough corridor, get help with your site for your project.

Sources

1. Indian Roads Congress, IRC:SP:19-2001, Manual for Survey, Investigation and Preparation of Road Projects (Sections 7, 8 and 12). law.resource.org

Frequently asked questions

What is the difference between reconnaissance and preliminary survey?

Reconnaissance compares possible routes from maps and a site visit. The preliminary survey measures the chosen corridor with instruments: traverse, levels and cross-sections.

How long does a reconnaissance survey take?

From a few days for a short urban route to several weeks for a long cross-country one, depending on access and the number of alternatives.

Is a recce needed for a short cable route?

Yes, even a one-day walk-over helps: it finds crossings, chambers and congested stretches before drilling or trenching is planned.

What maps are used in reconnaissance?

Topographic sheets, recent satellite imagery, geology and soil maps, and any records of existing services along the route.

What comes after the recce for a road?

A preliminary survey and then detailed design survey; for the detailed stage, see topographic survey for road projects.

Can a drone survey replace a ground recce?

Drones help on open ground, but they cannot see buried services or ownership issues, so a walk-over is still needed.

Written by Saniya Parveen · Technically reviewed by Rahul Rai · Updated 8 November 2026