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Introduction to GDMS Surveying
GDMS is National Highways’ technical information about the location and condition of all drainage infrastructure on their network.
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Given that GDMS inspection work is usually often carried out at night due to the high risks associated with working on busy roads, common phrases that are often used by the Areas in tender negotiations with contractors refer to how the contractor should behave when they discover that an asset cannot be inspected dues to its current operational condition (i.e. a pipe is full of silt, so how do we inspect it, but it’s the middle of the night so there is nobody I can call at the Area to ask the question regarding what to do next).
The following is a guide only and must not be taken for granted. The details of these kinds of terminology must always be negotiated and agreed between the client (The usually the Area) and the contractor, or between the contractor and the sub-contractor.
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Whatever the scope of work or the scheme extents, the process of delivering GDMS inspection data to the client using the specified standard always begins with the existing known data of the drainage network within the scheme. This is the beginning of the round-tripping process (described later in this document), and the '
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The contractor (or sub-contractor) MUST receive these shapefiles in plenty of time before they start work on site. |
Other questions that the contractor should always fully understand before entering into GDMS works include:
Scheme Extents – on motorways, this is usually described by the road description (i.e. M25, Junction 3 to 4), or by Marker Post IDs which are the small black, red and white posts every 100 metres along the side of all motorways. On non-motorways and all projects, this should always be accompanied by drawings supplied by the client outlining the extent of the scheme of work by an outline on a plan.
Then, the contractor should understand which parts of the road are included in the requested inspection data. Terms like ‘verges only’, ‘central reservation only’, ‘inner ring of the roundabout’ etc are common terms when understanding these needs.
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