There is big money poured into underground utility mapping. The older the city the bigger the problem. There are commercial mapping companies who specialise in offering a service in this area. Mapping involves many different tools and research is currently ongoing between the EU and USA and elsewhere to develop multi sensor tools to aid the process. Have a look at http://www.mappingtheunderworld.ac.uk/ for example.
The lines of sewers and some storm drains are often easy to plot because they are generally in straight lines between manhole covers (note though that the line of the pipe may not be directly below the cover). For nearly all other utilities you need other methods. Scars (reinstatements) of the highway can identify some utility paths, especially for recent works, but you will not necessarily know what the utility is below. Piggybacking off others who have spray painted areas to show utility routes might work for very local issues but they rarely show the full picture and is just provided as a guide to contractors to reduce risk and improve safety when excavating. A lot of utilities get damaged when contractors dig up the road for other utility repairs or upgrades. Traditionally contractors have used a simple tool called a CAT and Genny, which is combination of a “Cable Avoidance Tool” and a “Signal Generator”. The CAT can detect most but not all electrical cables and other conductors. In Generator mode a separate signal generator is attached to part of a pipe or other piece of the utility, like a valve, and the detector can then map this signal as it passes through the metal. For plastic pipes (HDPE and PVC mostly) there is minimal external means of identification other than using Ground Penetrating Radar and even then it requires a lot of interpretation, especially when there is a lot of other utilities in the vicinity. Mapping below reinforced concrete road slabs is very difficult. Not all pipes and cables are in use. There is a lot of defunct asset in the ground which you often don’t know whether is in use or not until and excavation is done and a verification process undertaken. There is also the added difficulty that most utilities lie within the public highway (Road or pavements) and safe access for mapping normally means shutting part of the street down. So in summary it’s a complex issue with no easy win. Sewers can reasonably be inferred along most streets but there are few options for the amateur mapper looking for other utilities in urban environments. Cheers Andy From: Tim Waters [mailto:chippy2...@gmail.com] Sent: 20 January 2015 13:07 To: Pmailkeey . Cc: talk-gb Subject: Re: [Talk-GB] Fwd: Underground services I'm also interested in underground cables and mapping communications routes, in particular the major internet "trunk" cables. My question would be, similar to tunnels and other somewhat hidden underground features - how would we represent lengths along the route where the positioning is unclear. Before better sources of positions become available, would straight lines in the database from A to B be allowed, or desired? Shouldn't these unclear, holding lines never be rendered? And, more interesting: how can we get better positioning information? Could the scars along roads be used to help interpolation of positions? Could we develop hand held instruments to detect various things? Does dowsing work? Can we use the markings sprayed on the pavement by utility companies to identify what's there? Cheers, Tim
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