"Dirty" Film Receives Rave ReviewsBy: Shafik Jiwani, Head of
GIS Section, Drainage Division |
| Contents Page | Al-Khabar Home Page | CGIS Home Page |
Local film enthusiasts are queuing for a glimpse of the Drainage's Division's recent release, "Dirty Hairy." Commented one reviewer, "The cinematographers have captured a true-to-life view of the grimy underbelly of big city life. It's rough, it's tough; a real rollercoaster ride through some of the meanest parts of Doha."
How was the film conceived? What was the underlying motivation behind making this cinema vérité gem?
While the GIS Section at Qatar's Drainage Division has acquired extensive information on the location of it's foul & surface water sewer networks, it has limited data about the internal condition of the pipes. This information is critical in maintaining an effective sewer system.
|
ArcView screen displaying sewers CCTV survey team dropping camera
into a manhole |
|
Though visual inspections are pos3sible for large diameter pipes, sending a survey crew into the sewers is difficult, time-consuming, and potentially dangerous. For the smaller pipes, this sort of inspection is simply impossible. However, visual surveys are essential.
The surveying of the inside of a pipe is a relatively new technology which has developed out of a need to avoid sudden collapses in the finely balanced infrastructure of a modern society. As public funding becomes tighter, the efficient use of those funds allocated makes good economic sense for managers.
The video camera industry has adapted its technology to a number of specialized uses, including surveillance, telecommunications, and the internal inspection of conduits. Though the use of Closed Circuit Television (CCTV) for sewer pipe inspection is fairly common in Europe and North America, it is still relatively unknown in the Middle East.
Cameras have been developed to suit most pipeline sizes from as small as 25mm diameter, used with a push rod system, to 2,000mm diameter pipes for which the camera is mounted on a remote controlled tractor and driven along the pipe from a surface control centre incorporated into a purpose built CCTV survey vehicle.
The video picture being captured by the camera is usually recorded on to a standard VHS video tape and further technology development has provided the survey engineer with a facility to add information to the 'live' picture before recording. This allows both graphics and text to be generated on the viewing monitor describing what can be seen in the frame of film which is then recorded along with the video image as a permanent record.
The Drainage Division has invested in a CCTV survey camera system from PearPoint Limited (UK) to collect structural information about the condition of its pipes and has a survey team working full-time on data collection. Defects noted by the survey include fractures, holes, water ingress, roots, debris, connections, etc. The data is collected in a standard format which has been adopted by the majority of British Water Agencies, consultants and contractors.
The Manual of Sewer Condition Classification was first published in 1980 to provide a UK national standard defect coding system for this type of survey work. This manual has been adopted as the basis for the Qatar National Standard which is under preparation. There are a number of items that have to be changed to suit the local climate, and the construction materials used during the development of Qatar's sewerage network. New codes have also been introduced which may allow computer assessment methods to be developed further.
In addition to providing full colour images, there are CCTV sewer survey systems that have the ability to change their view point from the traditional straight ahead perspective to a full 270 degree rotational view, providing engineers with the tools to generate an accurate condition report of both the main sewer and any connections joining the pipeline.
All existing manholes and pipelines have been previously surveyed and integrated into the national GIS, which makes it easier to define the sewer network areas for CCTV surveying. Maps are produced from the database showing relevant information such as manhole number, pipe diameter, pipe material, etc. The survey vehicle is then deployed to the area where it sets up the equipment at a chosen manhole. A jetting tanker is also provided for the survey team to clean the sewers with a high pressure jet of water before commencing the survey to minimize obstructions and blockages.
In addition to providing additional information for the GIS database with respect to site temperatures and gas level readings, the survey also verifies already collected information such as pipe material and pipe diameters, thereby increasing the confidence level of the information already stored on the database.
To conduct the CCTV survey, the camera is carefully lowered into the start manhole and manually pushed through the pipe until it reaches the end manhole. This requires careful coordination between the crew guiding the camera and the supervisor monitoring its progress on the video screen.
The camera is designed for very low light levels, but carries auxiliary bulbs to illuminate the inside of the pipeline, if necessary. Housed in the specially equipped survey vehicle is the monitor with a camera control unit (CCU) and a video cassette recorder, which is used to record the picture in VHS format. During inspection, data is captured on high speed, removable and re-usable media prior to conversion to CD or digital video disc (DVD). This allows inspection data to be quality controlled before permanently recording it on the archive media. At the moment, Drainage Division is converting all its standard analog VHS format videos through a Video Enhancement Module and an MPEG1 code Video Compression Module (in real time), thereby creating a better quality, randomly accessible video. One of the major advantages of using digital video over an analog system is that the former does not lose quality over time. When a CD is copied, the product is as good as the original, with no loss of quality.
The camera has an in-built measuring device to identify the distance from the start manhole to the picture being viewed on the monitor. The distance is automatically stored on the video image, which is invaluable since it can be used to accurately locate a previously unknown problem. The CCU also allows text information to be added to the 'live' video recording. This allows defects such as debris, roots, protruding pipes or structural problems to be recorded directly onto the video recording.
The CCTV survey also provides accurate distance measurement for the location of any buried manholes, allowing it to be exposed and raised without extensive excavation. Similarly, other information such as blockages or structural problems can be relayed to the Operations & Maintenance Section of Drainage Division so that cleaning works or repairs can be carried out efficiently. For example, if the camera shows a large root mass at 25 m inside a pipe then this area can be targeted rather than cleaning the whole 75 m of pipeline.
When the survey is completed for a pipeline, a report is written using a Standard Condition Survey Sheet, which allows each defect to be graded through a unique coding system. There are over 130 unique codes used in the identification of the various known pipeline conditions. There are three basic categories that codes have been developed for :
- Structural Condition - giving information relating to cracks, fractures, displacements, deformities and internal surface conditions.
- Service Condition - which states the condition and cleanliness of the sewer at the time of the survey.
- Construction Features - relates to the type of connections and junctions and their condition.
Each code is usually enhanced to give additional information about the defect/feature these are then combined to give the an overall condition grade. For example if a fracture is located at a certain distance from the start manhole then the coded data entry would include the position of the fracture in the pipe as a clock reference, if it was single or multiple, if there was any pipe deformation, if there was any infiltration associated with the fracture, etc.
The codes are then entered into a database and a score is determined for each defect. Serious structural defects, such as open fractures, are given bigger scores than small defects like debris.
An application assesses the codes and provides the engineer with information about each pipeline which can be displayed graphically or as a pipeline schematic. The information is categorized to give an aggregate score for each 1 metre section of the pipeline which is then used to give an average pipeline score from manhole to manhole. These are automatically converted into a Pipe Classification Number between 1 and 9, where 1 is an 'as new' pipe and grade 9 has serious structural degradation.
The information collected from these CCTV surveys is available through the Drainage Information System '97 (DIS '97) where it can be instantly accessed, queried, reviewed and analyzed through the GIS interface.
|
CCTV form displaying pipe
classification details |
|
The CCTV module in DIS '97 allows the user to click on a sewer line of his choice to show a video of the internal condition of the pipe. Displayed together with the video screen image is a simple 'live' line plan view of the pipeline with all it's features and defects highlighted simultaneously with the location of the camera's video picture. Displayed, in standard coding format, along the sewer will be features such as connections and points where attention is required. These may be structural defects, roots, debris, protruding services, inflow/infiltration, etc. By clicking on a highlighted coded point, a frame of video at that particular condition is immediately shown on the screen, unlike video tapes that can only be accessed in a linear fashion by moving the tape forward or backwards to a selected location of interest. The standard fast forward, rewind, frame advance/reverse, and pause video controls are available as buttons, as well as user-designated looping of incidents which continuously repeats a chosen section of the video. Another feature of this application is that access to the GIS attribute data detailing all the major information about the pipe, location, size, material, etc. is made through the click of a button.
Using DIS '97, it is also possible to highlight all pipes having a certain Pipe Classification Number (e.g. all number 9 pipes) in an area. Statistics can be generated to give the total lengths of sewer and the pipe diameters involved for the chosen value. This data can then be used to justify budgets and accurately target areas for replacement, lining or simply to carry out local repairs to sewers.
Having access to CCTV information gives managers greater confidence that funds are being spent correctly and allows rehabilitation and preventive maintenance programs to become more organized, efficient and effective.
"Dirty Hairy" is a 'must see' when it plays at your local cinema. An Oscar is in the pipeline.