HT/LT Underground Cable Route Mapping with GPR

Rates and page checked: 23 October 2026

What do HT/LT underground cable mapping services cover?

A new 11 kV, 33 kV or LT cable shares its corridor with services laid by many departments over many years. HT/LT underground cable mapping services exist to find those services before your excavator or drill head reaches them. Our crews scan the full width your work order covers and record:

• water mains, sewers and storm-water drains;
• gas distribution pipes;
• telecom and OFC ducts;
• existing HT and LT cables, street-lighting cables and earthing conductors;
• unidentified objects that do not match any available record.

Each detected line gets a plan position against your route, a measured depth where radar provides one, the method that found it, and a note on how firmly it can be relied on. The same service also handles underground power cable tracing on its own, for diversion or shifting jobs where an existing cable has to be followed before it is moved.

The service is built around EPC contractors and DISCOM-appointed contractors who must clear a route before trenching, HDD or cable pulling. Utilities planning a network-wide programme will find the asset-side view on our power utilities page.

How does an electric cable route survey using GPR run, step by step?

1. Work order review. We read the route drawing or KML, the cable specification and the survey clauses of your contract, so the field plan matches what your client will check.
2. Records and walkover. Available service records are collected, and the crew walks the route noting chambers, valve covers, feeder pillars, cable markers and access limits.
3. Longitudinal and cross scans. GPR lines run along the route and across it; 3D or high-resolution grids are added where services cluster together.
4. EM sweep. Conductive lines are traced with electromagnetic locators, passively for energised cables and with an applied signal wherever a connection point is available.
5. Crossings. Road, nala, canal and rail crossings receive extra passes and a separate record.
6. Marking. Results are checked on screen, then painted on the ground in utility colours with approximate depth.
7. Report. The survey report lists every detected service, the depth reached in each section, no-access stretches and method limits; an L-section is added when ordered.

On a long corridor, crews mark the stretches your excavation team will open first, so trenching can begin while scanning carries on further up the route.

How are road, nala, canal and rail crossings handled?

Crossings are where cable jobs most often stall. The new cable either drops under the obstacle in an HDD bore or crosses it in a deep open cut, and either way the services hidden under the crossing decide the design.

We treat each crossing as a separate block rather than as part of the running route. The scan extends past both the planned entry and exit pits, so the bore designer can see what lies around the pits as well as beneath the obstacle. Culverts, nala beds, canal lining edges and rail embankments are recorded together with whatever services were found near them.

Railway, highway and canal land normally needs the owning authority's permission before anyone works on it. Obtaining that permission, along with any traffic arrangements, is the project's job and is billed apart from the survey; our crews work within whatever window is granted. For bore planning, see the guide to HDD crossing surveys and our HDD service, which runs on 18 company-owned rigs.

What changes when live HT cables are already in the corridor?

Nothing has to be switched off for the survey. Radar and locators work from the surface, and an energised cable generally helps the locator, because the current it carries radiates a field that can be picked up without any connection.

The real difficulty is separation. Two or three circuits laid side by side can merge into one broad signal, so the radar record is used to count and position the individual cables and to mark the outer edges of the group, not only its centre. Where a new trench must run close to an existing HT circuit, the report names that stretch and recommends hand excavation inside the marked band.

Trial pits can be dug on request at points where a depth or an identity has to be proved before any machine work starts nearby.

Can GPR be used on underground EHV transmission cable routes?

Yes, with honest limits. A GPR survey for power transmission lines laid underground – 66 kV, 132 kV and higher EHV cable – follows the same method, but the design questions are sharper. EHV cables are often laid deeper and in wider trenches, joint bays need extra room, and major crossings are frequently bored.

Radar reach is set by the ground, not by the cable's voltage. Signals carry further through dry, sandy soil, while wet clay and saline ground absorb them sooner. For every section, the report records the depth that radar achieved, letting a designer judge whether the survey covers the full depth of interest. Where it does not, boreholes or trial pits can be ordered as extras to confirm what lies below.

For EHV work we generally suggest ordering the L-section option, because a continuous depth profile of existing services is what a deep-trench or bore design leans on most.

When should you add the L-section option?

For many LT and 11 kV trench jobs, plan positions with spot depths from the standard route survey are all the excavation crew needs. An L-section GPR survey, at ₹32 per metre, plots the depth of each detected service over the whole route length. Order it together with the route survey if your contract asks for a longitudinal profile, if the route is congested, or if HDD sections will be designed from the survey data. Adding it later means sending a crew back to site, which costs more than doing both in one pass.

What does an HT/LT cable route survey cost?

Pricing is per running metre of route scanned: ₹24 for the standard survey and ₹32 with an L-section. For a 60 km 11 kV package, that comes to ₹14,40,000 for the standard survey or ₹19,20,000 with the profile, both before GST.

• Longer orders are cheaper per metre: the rate falls by a quarter beyond 100 km, by 40% beyond 500 km and by half beyond 1,000 km. The reduction covers the entire order once a slab is crossed, so 110 km costs less in total than 100 km.
• Anything under 4 km is charged as a 4 km job.
• Beyond Delhi NCR, every project is also subject to a ₹1,00,000 floor.
• GST is extra, and mobilisation, night-shift work, traffic arrangements and permissions, and CAD/GIS drawing sets are quoted separately.

The full breakdown by slab appears in our GPR survey price list.

Working on a Gujarat or MGVCL cable package?

Contractors with MGVCL conversion or underground work in central Gujarat can read about local ground, river and rail crossings and dense city stretches on our Vadodara cable route survey page. The wider state picture, including UGVCL, DGVCL, PGVCL and Torrent Power areas, is on the Gujarat GPR survey page. Mezux Touch holds no affiliation with MGVCL or any other distribution company; our client is whoever places the survey order.