Helsinki Water has been a client of DigiSewer® for some time, with over 300 km of its sewer pipe network having already been surveyed using the technique. The recent project comprised the inspection of five kilometres of sewer pipe of between 300 mm and 500 mm in diameter, which included PVC, concrete and clay pipe materials.

Only five working days were required from the beginning of the survey work to the completion of the data collection. In conjunction with this efficient data collection period, a full analysis of the data was completed in only four hours. The entire survey, from the inspection run to the presentation of the completed and analysed survey on DVD, was achieved in five and a half working days. Such an accomplishment could not have been expected using any of the traditional CCTV survey systems available today.

Digital technology

The DigiSewer system comprises a 360 degree scanning camera mounted on a robotic, remote-controlled, wheeled tractor. The tractor travels through the pipe at a constant speed. The camera continuously scans the pipe’s inner surface creating a series of adjacent section views covering the pipe’s circumference. Specially developed computer software processes these scanned sections and stores them for further analysis as a single complete record of the survey run.

The software is capable of automatically recognising pipe joints and lateral connection positions within the survey data, which are highlighted in the stored data. Pipe defects can be subsequently viewed by an analyst quickly and efficiently, immediately after the survey is completed.

The continuous scanning technique of the DigiSewer at advance speeds of around 13 metres per minute has automated data gathering and storage. This technology eliminates the potential for human error that can occur with more traditional surveys that requiring the survey to be stopped by the operator in order to inspect suspect defects during the course of a run. It also eliminates the potential for defects to be overlooked should an operator be distracted during the observation process. There is also no requirement to pan, tilt or zoom the camera towards individual suspected defects as all relevant information is recorded on the single continuous pass.

This enables DigiSewer survey runs to be completed far more quickly than is possible with conventional CCTV surveys. The automated data capture, at higher resolution than standard video recording, also ensures that the survey data is acquired with consistently higher detail than is achievable with standard CCTV survey techniques. This in turn ensures that, once the survey run is complete, the data analysis is easier, faster and of a higher quality than that of traditional inspection systems. Data Presentation

The digital format of the inspection data collected allows the survey results to be manipulated and presented in a variety of ways, simultaneously. This reduces significantly the number of man-hours required for the manual analysis of the data by eliminating many hours of unnecessary video footage observation by the analyst. As well as the standard forward view of the pipe being surveyed, the built-in DigiSewer software generates a full pipeline view from the start of the survey section to its end in a single picture.

The software also allows the analyst to zoom in on any point along this survey for a closer inspection of any suspected defect. This zoom view can be displayed alongside the whole pipe view. Joint and lateral positions are automatically displayed on these views, so that other potential defects can be easily recognised at other positions along the pipe length. The software also allows the data to be marked, commented on and restored immediately on screen. Up to five kilometres of survey data can be recorded manipulated, marked and commented on using a single DVD. The DVD can be presented to the end user with free viewer software for easy access.

High value results from high value data

As the survey run progresses, the scan data is automatically stored in a format that can be ‘unwrapped’ by the image processing software. Therefore, individual and adjacent scan sections can be strung together to form a continuous, single, full survey length, two dimensional image of the pipe’s inner wall.

The presentation screen offers full pipe survey length; forward and side scan views of the pipe wall scan sections. This enables an analyst to process the survey data quickly and easily and to pinpoint defects that have not been automatically highlighted as either pipe joints or lateral connections. Analysis is quicker and easier and the software allows comments and measurements to be made at each defect which are then stored as part of the base data. The software also allows the analyst to pan, tilt or zoom on the images to take a closer look at potential defects, subsequent to the survey data being collected rather than during the survey itself. This is a major time saving solution for the survey operation.

The system also carries a built-in inclinometer which records the slope of the pipeline at all points during the survey. The data recorded by this unit is displayed alongside the scan data to show the analyst the inclination of the pipe at any given point and over any length of the pipe. This highlights any troughs or humps in the pipeline that may cause flow problems. The data produced by DigiSewer has been designed to integrate with and provide instant data access via most, if not all, commonly utilised sewer survey reporting software, particularly those based on WinCan V8. The data field requirement itself is designed to be as compact as possible in order to minimise storage requirements and to enable electronic transmission of the data within an acceptable time frame. For example, inspection data from a survey of up to five kilometres in length can be stored on a single standard DVD disc, as compared to around 700 metres for traditional video recording.

DigiSewer efficiency vs traditional CCTV survey

The primary Rovver tractor system together with DigiSewer, using a single camera, can complete conventional CCTV surveys as well as DigiSewer operations. As compared with traditional CCTV surveys the volume of data produced by DigiSewer, which utilises DSP video technology, is low, making it possible to store large surveys on a single DVD. The software for DigiSewer utilises an industry standard reporting system, such as WinCan V8. This means that little, if any, retraining is required for operators or analysts to interpret results and produce the required reports. This, alongside with the automatic recognition of joints and lateral positions, ensures that the DigiSewer operation is efficient and cost effective, with significant time savings as compared with traditional CCTV interpretation.

The continuous data collection achieved by traversing the camera unit through the survey pipe at constant speed also means that stoppage time for individual defect analysis is eliminated making further time savings. Pan, tilt and zoom functions for closer defect inspection is achieved electronically at the analysis stage. Surveys are completed onsite more quickly, thereby reducing, if not eliminating, local disruption to traffic, businesses and everyday life.

Where a defect is suspected, the software also allows an instant zoom on the point in question without having to run through lengthy video footage. At this point the software also produces a side view and front view of the suspected defect position, enabling a fuller analysis. The analyst can then add highlights, comments and remarks on screen, all of which are added to the base data scans and stored for future reference by client engineers. Once the data is presented to the client, further comments, pan and tilt viewing and zoom can be carried out by the client’s engineers as required for their own maintenance and rehabilitation programs, without the need to refer back to the survey company.

Measurements can also be made on screen to determine the size and shape of a defect. All such measurements can be linked directly to the reporting software output. The inclination of the pipe at any point is also displayed using data from the built-in inclinometer within the DigiSewer system. The DigiSewer saves time and provides better information to make more accurate decisions, making it a smart investment into future technology of automatic video analysis.