Introduction

Various spatial imaging systems can be used to help map and monitor our coastal and marine resources. Some of these tools are deployed from airborne platforms to map the coastal zone, some onboard sea-going vessels to acquire both surface and underwater spatial image encoded data.

In some cases, this data may be best acquired on the ground by survey personnel. This section describes some of these systems and how they operate.

 

 

Recently acquired underwater encoded footage, Irish Sea (courtesy of Irish Marine Institute and Coastal & Marine Resources Canter)

Advantages

    Broad range of imaging and navigation sensors

    Proven technology

    Multi-platform tool

    Advanced data processing & fast turnaround time of data

Applications

• Sea defenses, coastal stability, erosion, flood risk mapping
• Underwater sea-bed survey (flora, fauna, aggregate & minerals)
• Waterway network navigation, tourism promotion
• Oil pollution monitoring and mapping
• Detailed beach site investigation
• Fisheries management

Aerial video frame acquired using a standard Hi8 video camera depicting measurement of shoreline feature

This system will vary slightly depending on whether it's deployed from the air on an aircraft, onboard a surface vessel or indeed on the ground along the coastline. There are a number of elements that are common to all three environments regardless of what platform is used. Normally, a video camera and a digital SLR camera (3 MegaPixel to 14 Pixel) is used. A heading and reference system (AHRS) is optional. There are various approaches to recover offsets of any towed underwater frame or sled. Full 3-D positioning and measurement is possible depending on sensors used. Normally, cameras are fully calibrated allowing monscopic measurements to be carried out. The video provides the continuous footage of the seabed or coastal zone (from the air) while the digital camera can be used to acquire detailed views of features or events. The data acquisition software can be modified to allow the operator to record 'event markers' as well. Alternatively, the digital SLR camera can be preprogrammed to acquire continuous detailed images together with associated navigation.

Simplified diagram depicting a data acquisition system capable of surface and sub-surface mapping

Coastal zone spatial video

Processing

The video 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 CamNav. 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.

Digital SLR Camera Image

Digital SLR images and navigation are usually processed separately but require less attention since these images already exist in digital format. The only task that remains to be carried out is building and synchronising the navigation with video image data. This is accomplished using GPs time. Any events or tagged images, recorded by the observer during acquisition, are also processed and the data is structured so that the browser can easily access the relevant datasets

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 for underwater mapping 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 coastal or marine 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.

Additional products

Below is an example of a mosaic or 'strip-map' compiled automatically using 75 video frames over Scolt Head Island (dynamic sandspit), Norfolk Coastline, UK. These mosaics can be rapidly acquired and constructed at very low cost. Sometimes these image compilations are used as 'quick looks' or can also be used as a simple mapping base for more detailed digital camera images. The latter feature can sometimes be useful when little or no ground control is available from conventional map data.

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 Browser

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.