Abstract
The core principles of collecting good quality data from site for creating CCTV inspection reports including some explanations of how to avoid common mistakes.
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The PLR Naming Convention
Most global drainage inspection standards include a system for naming pipes based on either the upstream manhole ID or a combination of both the upstream and downstream manhole IDs. The Manual of Sewer Condition Classification (MSCC) defines the naming convention for WRc pipe and sewer inspection using the Pipe Length Reference (PLR) system at all times:
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This list can be extended or modified as required by the user because it is only a suggestion for a simple and robust naming convention that is easy to follow and is informative. It should be remembered that the upstream and downstream node ID fields in the WRc reporting in WinCan VX only allow for 10 characters maximum. The reasons for this are because the manhole naming convention described in Appendix A of the MSCC only require 10 characters to name any manhole in the country, and the xml data format exchange file also limits this field to 10 characters. This naming convention is described in detail in Understanding STC25 Manhole References.
In short, the really easy way to fix the commonly seen data problems like that describe above is to use numbers in the gully (or whatever upstream node exists on site) references, like this:
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Good data with no duplicate PLRs.
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The most common time that we see data problems like this is when people inspect upstream from an inspection chamber on site (let’s call it MH1) and they push the camera up 2 or 3 branch lines coming into chamber MH1. They label the upstream node as LatA, LatB and LatC, which then means that the PLRs are LatAX, LatBX and LatCX. So far, so good. But now they move on down the main line to MH2 and do the same thing again starting at A, so they inspect from MH2 upstream to LatA and LatB, making the PLRs LatAX and LatBX. Now we have 2 LatAX and 2 LatBX in the project and already the data is starting to fall apart. And of course they will swear blind that the pipes are different pipe because they are connected to MH1 and MH2, but this is just not the case in the data. The data sees them as the same pipe because they have the same PLR. Some pointers to help you demystify the nomenclature:
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Because the name of the pipe (the PLR) is defined by the upstream node ID and the PLR Suffix, this allows a manhole or other node to have up to 3 outgoing pipes. This may seem a strange concept to many CCTV inspectors, particularly at a domestic level because they have very likely never seen a manhole with 2 or more outgoing pipes. However, this is extremely common in highways drainage and is constructed this way by design because on highways (more than any other place) it is essential to get the water off the road at all costs and as quickly as possible during heavy rainfall events so as to avoid traffic accidents.
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Good Site Drawings
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Understanding STC25 Manhole References
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