Introduction

This single or multi-camera system can be configured for pipeline/power line mapping or monitoring operation. This system is ideally suited to  record location of events and features along the right of way (ROW) since the video's field of view (FOV) matches the 200m to 500m swath width usually required for this type of survey work.

The pipeline and powerline video mapping systems is

    Ideally suited to monitor the 250m swath width of pipeline or transmission line corridor

    System has been tested on a range of fixed and rotary wing aircraft

    Video system can be integrated with higher resolution DSLR cameras

    Lightweight, rapid data collection tool

    Stereo coverage, along track mosaicing and in-frame measurement available

Image depicting measurment of line segment from pipeline 

Positional accuracy is typically within the tens of meters since spatial video is recorded from onboad fixed wing aircraft or helicopters. Airborne camera mapping systems typically require orientation (pitch, roll & yaw) as well as X, Y, Z position, digital elevation model (DEM) data in order to calculate ground target position. BlueGlen's software can process this data but accurate positioning and orientation sensors are usually expensive. BlueGlen offers a range of alternatives. Image quality will depend on choice of camcorder but expect reasonable quality images (768*576) in size. Video cameras can be calibrated and so allow objects and features within the image to be positioned and measured. This calibration is based on a monoscopic camera model using a perspective transformation algorithm.

This system is constructed using two camcorders (forward oblique and near vertical) and one CamNav unit. Most video cameras are suitable including black and white, colour, low-light, infra-red or FLIR models. However, it's always best to check first with BlueGlen's technical unit. Normally, separate, optical sensors together with DV VCR 4.5 hours recording time) are used These digital VCRs have the advantage of recording higher quality images and longer play tapes.

Power consumption for this multi-camera configuration can be usually operated using batteries or from an inverter attached to the aircraft's 28VDC supply. A mount is normally constructed to maintain the cameras in a stable position outside on the skid, under the wing or attached to the wing strut/step. This mount contains separate screw-in plates for each individual cameras. These can be adjusted enabling the camera to be rotated in pitch, roll and yaw.

Typically, choice of lens and flying height determine swath width and spatial resolution. During flight, GPS positioning is encoded onto the VCR using the CamNav encoder/decoder. A green light indicates that the GPs fix is good and recording is operating correctly. Events such as damaged conductors or 'overhanging branches' along the pipeline or powerline corridor can be 'marked' or tagged and processed back on the ground. A laptop together with additional software provide flight planning capability and 'moving map' display for navigation functions.

Processing

The encoded data is processed using a frame-grabbing card and a suite of software located on a standard PC machine. The tape containing the encoded GPs is now decoded using the Camcorder, which is connected to the VCR. Two output cables containing the video and GPs data are then connected to the frame-grabbing card and RS-232 serial port respectively. 

This is usually a two stage process. 

Processing - Stage One 

Frame-grabs frames at a rate chosen by the operator. These frames are tagged with GPs time and saved onto hard disk. At the same time, the GPs data is logged at the serial RS232 port and saved in a file.

Screen-grab of the spatial video processing system.

Processing - Stage Two 

The second stage involves de-interlacing the digital video images and producing digital images 768*576 in size. An ESRI 'shape' navigation file is constructed from the logged GPs data. This file contains all the navigation data together with references to image names. It will take approximately 1.5hr of computer time to process one hour of spatial video data. Most of this time is required by the frame-grabbing module, which can only operate at normal video speeds.

The browser integrates the various video, GIS, database, measurement modules into an easy to use lightweight application. The main application window is split into video (right), GIs (left) and database (bottom left) displays. The user can load up any survey using the pull-down menus. A metadata layer is usually constructed beforehand and enables various surveys to be loaded with minimum fuss.

Screen-grab of a ‘basic’ browser system

The user can navigate through the spatial video data using the video controls, or by double-clicking on some point on the map or by clicking on a record within the database module. The video plays in the main video display as well as the three thumbnail displays. The position of the boat or vessel is dynamically displayed on a moving map. The usual pan/zoom/identify functions are available. Replay speed can be adjusted and various views can be turned on or off. Left or middle,  views can be chosen by clicking on the any one of the thumbnails below the main video display. Positions of pipe or power line objects can be measured using a perspective transformation algorithm  (based on a monoscopic camera model). This feature together with a data input module enables route objects to be entered into a database. Full spatial and imaging geometry of the object or feature are also stored. This allows the object to be quickly displayed later once the user double-clicks on the database record. This database together with associated video images can be easily exported to other mapping/imaging system and/or databases. The camera 'footprint' or projected FOV on the ground can be dynamically plotted on the map display. This aids user orientation and is a feature that can be switched on or off.

Additional features

Automated Mosaicing

Automated mosaicing or strip mapping is easily accomplished using the near vertical camera view. This feature enables hundreds of meters even kilometers of pipeline or powerline corridor images to be seamlessly 'stitched' together offering an along track 'synoptic' view. This image composite can be readily georeferenced using control points form GPs or base maps.

Stereoscopic viewing

A wide range of base to height ratios are available, since typically between 25 and 30 frames are captured per second, allowing user to view relief. This feature is useful for interpreting difficult areas of terrain, for example areas of changing relief or variable vegetation. Stereo glasses or ability to view in stereo are necessary to view two examples below

Stereo Pair Example 1 (Time separation = 1sec)

Stereo Pair Example 2 (Time separation = 1.2 sec)

CamNav Mapper™ Multi Camera Services

Blueglen prefer to work with the client to devise the most cost-effective and 'fit for purpose' solution for client's application. 

Acquisition

The client can acquire the CamNav Encoder/Decoder box and carry out the data acquisition themselves. Alternatively, BlueGlen can carry out any type of survey on your behalf.  Regardless, BlueGlen has a wealth of experience in choosing cameras, recorders, mounts, power distribution units and can help the client decide on best options.

Processing

The multi camera processing suite can be purchased, rented or BlueGlen can undertake the processing on behalf of the client.  BlueGlen would provide remote or on-site support should the client purchase the processing module.

It is possible to setup a number of processors in parallel, to process multiple videotapes at the same time.

Browser

A single browser license is included with a multi camera purchase.  Any number of extra licenses can be obtained or a corporate license might be a more suitable option.

Normally a browser requires some customisation.

Level 1 Brow ser

Simple digital interactive map and GPS encoded video viewing system that allows the client to view data using PC based video control buttons and a 'moving map' display.

Level 2 Browser

Same as level 1 plus a database interface for data input, in-frame measurement, automated report generation, image processing functions, strip mapping, stereo viewing.