Technology behind aerial leak detection services and equipment.
Synodon developed the Simultaneous-View Correlation Radiometry (SVCR) technology and implemented it in the realSens™ gas detection system. SVCR is a variant of the Gas-Filter Correlation Radiometry (GFCR) technique.
SVCR differs from other implementations of GFCRs in two major aspects:
Firstly, classical density modulation methods, such as selective chopper, pressure or length modulations, are replaced with a static design with two cells. The incoming electromagnetic radiation split in two beams and each beam is directed to a cell. One cell is empty and leads to the reference signal and another one is filled with a sample of the gas of interest and leads to the correlation signal. Prior to being sampled by infrared detectors, the instrument spectral band is determined by an optical filter. A simplified graphical representation of this design is shown here together with a picture of the completed realSens™ instrument.
Secondly, the main realSens™ instrument is accompanied on-board by a set of auxiliary instruments that provide data sets synchronized in time and correlated in space with the gas information. These instruments are required for two reasons. On one hand, they provide a visual reference for the surveyed area and, therefore, a visible camera has been added to the instrument package. On the other hand, the very high gas sensitivity set for the realSens™ measurements require a more complex and accurate modeling of the expected incoming electromagnetic radiation than what has been used in the past with other GFCR-based systems.
An example of a dataset used in this analysis is that derived from a thermal camera which provides accurate temperatures of the surveyed surface. The needs for accurate timing, position and instrument orientation were addressed by adding to the system a GPS receiver and Inertial Measurement Unit working synchronously. Additionally, the GPS receiver can trigger camera image acquisitions at configurable rates. The instruments are installed in an enclosure that is attached to a helicopter through a custom mounting frame. Data from all instruments is collected by an on-board computer and stored for post-flight processing. That processing takes place at Synodon Inc’s Data Processing Centre and consists of several steps that lead to the end gas concentration report.
Simplified representation of the process.
A pictorial representation of the enclosure is shown above. The main realSens™ instrument is the blue-green device in the centre of the system. Click on the tabs below for the process:
In a first step, the various data sets are correlated using time stamps, platform position and attitude data collected during flight and instrument relative position and angular alignment determined prior to flying.
Secondly, the raw realSens&trade instrument data is “mixed” with spectral and temperature data using a set of complex algorithms to model the incoming electromagnetic radiation and evaluate the amount of gas of interest present in its field of view. At the end of this step, geo-referenced images of the detected leaks are produced.
Thirdly, visible images corresponding to detected gas emission positions are ortho-rectified.
Finally, GIS-compatible image products are created by superimposing the gas images available from the second processing step over their corresponding ortho-rectified visible images. This is the main end-product that Synodon offers to its customer together with a detailed report on detected gas emission locations.