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How can the image resolution of analogue cameras be checked? The image resolution for cameras with analogue image transmission should at least be aligned to the established S-VHS standard. It can be checked prior to the inspection by monitoring a test pattern that is represented via the camera objective lens in full frame (see image). (Image: Example for the test pattern according to DIN 25435 part 4 to check the image resolution) |
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Generally, the analogue inspection data are digitised directly in the inspection vehicle. In accordance with [WIKIa], the advantages of digitalisation are:
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(Image: Picto Video Film Filmrolle blau) Video compression forms part of the digitalisation. It serves to reduce the data rate of a digitised video signal, thus simplifying its storage or transmission. Achievable compression rates usually range between 1:5 and 1:200 [Wiki2011b]. Depending on the compression format, the video information is simplified and summarized by relying on the deletion of redundant image information and the deficiencies in human … |
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(Table: Compression Formats for Digitisation - Comparison) |
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The established formats in the field of sewer inspection are MPEG-2 and MPEG-4. An essential requirement for the video compression is that the quality of the images replayed in a MPEG format must not be significantly lower than the analogue recording or image representation during the inspection prior to the image conversion. Basically, this should also apply for the digitalisation of analogue video tapes. For that purpose it has to be known at which … |
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The presented CCTV inspection systems for sewers and drains but also manholes all require a control unit. This serves to control the TV inspection system as well as to record and store data and can be designed both as a mobile system and as a stationary system (inspection vehicle). In both cases, it usually consists of a monitor, user interface with keyboard and operating lever as well as various connections, computer and software. (Image: Mobile … |
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Mobile control systems in the form of a control box, control desk or monitoring panel are portable and are mostly used for the inspection with push cameras for sewer sections, connecting sewers or drain systems that cannot be accessed with inspection vehicles. These systems include:
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The control box serves to supply the camera with power for the lighting and, optionally, its drive. The inspection is monitored via a colour screen. The control of the cart, camera and lighting is realised via operating elements (joystick, keyboard). Additional displays indicate operating conditions and failures, additional operating elements serve for the system’s configuration. Additional equipment allows for the insertion of texts and symbols … |
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Usually, the vehicle platform for inspection vehicles is a minibus with a weight ranging between 3.5 t to 5.0 t. These minibuses are equipped with a winch and a control centre toolbox. Both rooms are functionally separate and designed according to ergonomic aspects to ensure a smooth workflow. (Image: Inspection vehicle for the inspection of sewers and pipes of the company Rico) (Image: Inspection vehicle for the inspection of sewers and pipelines … |
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The tool box that is located at the back of the vehicle includes the following components:
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The cable winch mentioned above should be equipped with a swivel-mounted extension (cable loom) that allows for an exact positioning of the camera above the manhole and its lowering right down to the invert. When using this equipment in standard manholes/-structures, no staff is required to access the manhole (to position the camera in the invert or the turning roller for the camera cable). The cable winch should be equipped with an electronic wind-… |
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The camera, cart and winch are controlled from the viewing area. It contains the control unit, which basically includes the following components:
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How is the position of the camera in the sewer line determined? The length measurement for determining the position of the camera usually works according to the following principle. The camera cable is pressed against a measuring wheel by rollers on its way through the duct or line. The rotations of the measuring wheel can be used to precisely determine both the unwound length and thus the position in the line as well as the feed speed. For this purpose, … |
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Apart from the used hardware, another essential component of TV inspection systems is their software that allows for the control of the system, data transfer, processing and storage, as well as a multitude of image representation modes that are implemented by means of its additional functions. The key task is the individual determination and documentation of all relevant sewer conditions that are captured by the camera and, if required, also by additional … |
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The software that is used for a survey of the actual sewer condition serves to capture, record, convert and file sewer inspection data. The following functions should be included:
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The documentation of a visual inspection measure should consist of the following parts:
(Image: Picto Desk Storage Schreibtisch Ablage Archiv) (Image: Picto Video Film … |
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The report on the visual interior inspection should contain a summary of the inspection project as well as individual reports on all objects of investigation (section, manhole, special structures, etc.). The individual reports should include the following information and minimum content:
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(Image: Picto Foto Images Fotoapparat) Photo documentation: if required, photos shall be presented on photo base sheets that include at least the following basic information:
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