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Would this combo detect differences in soil temperature in proximity to the release due to the higher temperature of pipeline fluids or would the surface temperatures be affected by the volatilization of the released fluids?

I know this technique is being used currently and I am just curious about the process by which it would be able to determine a release point.

  • I'm not sure why lidar would be useful. Would you compare one surface to another to see a change in volume? – jvangeld Jun 17 '14 at 20:09
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    I think the lidar is just for high accuracy elevation data. .. a base map for them to show heat spectra on.... perhaps it is also used to corroborate the heat signatures and normalize a close low value to a distant high value type situation.... – c0ba1t Jun 17 '14 at 22:05
  • What specifically are you trying to detect? Can you point us at a link/publication where these methods are being used? – Aaron Jun 17 '14 at 22:34
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    Leaking gas from pipeline networks.... mostly dry gas, I am afraid I can not give any more detail, it is a private sector operation I happen to know about and was just trying to discover the mechanism as I though it was very interesting. It is predominantly dry gas... methane and stuff.... – c0ba1t Jun 18 '14 at 15:37
  • Would methane (or something similar) reflect in the NIR, or would you need thermal data to capture this? If you would need to rely on thermal data, my concern is that the resolution of available products (100m LANDSAT 8, 1km AVHRR & GOES) would be too coarse relative to the size of a potential release/leak point. – JWallace Jun 18 '14 at 15:52
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The use of infrared data (presumably gathered by a FLIR camera) can be used to detect petroleum releases, but the FLIR approach has several issues... Mainly, background noise. Two approaches are commonly used:

  • A temperature differential between the surrounding soil and hydrocarbon being released can be see on the FLIR camera
  • A illuminating source (laser, sun, etc.)... With a spectrum that includes the absorption band of the hydrocarbon being released. Using a FLIR a contrast difference can be seen caused by the hydrocarbon absorbing the wavelengths in its absorption band.

Some of issues with the FLIR approach are: The viewing angle between the illuminating source and the FLIR need to be just 'right' to see any contrast. If the camera is mounted on an airborne platform, it is very easy to miss a hydrocarbon release. With a large release, viewed on the ground, with time to walk around the leak site... a hydrocarbon release can be observed. Using the temperature differential method, one must verify good contrast between where a leak occurs and the surrounding earth. For crude oil (normally warm), observations in the early morning (before the surrounding ground heats up) are best. For natural gas, early afternoon might be better (after the surrounding ground heats up).

Using DIAL LIDAR has many advantages to the FLIR approach (accuracy, sensitivity, and speed). The LIDAR does not require specific ground temperatures, and because the system uses a laser, the viewing angle problem goes away. Also if the LIDAR fire rate is sufficient, it can be put onto an airborne platform, and flown very quickly.

A possible combined approach could be to use a LIDAR for initial leak detection and then follow up with a FLIR (on the ground) to identify where to expose the pipeline for repair.

-Mark

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Differential Absorption LiDAR (DIAL) can assess gases releasing by scanning the target with (at least) two wavelengths in the electromagnetic energy spectrum:

  • one wave length that is absorbed by the gas of interest and
  • one that is not.

By the difference in the absorption of this two wavelengths it is possible to account for 2D and 3D gas concentration profiles. As long as the LiDAR system has a GPS one can map specific leaking points.

Here is one brief explanation about how DIAL system works from Chambers et al. (2006)*.

DIAL is a laser-based optical method that can measure the concentration of a gas species at a remote point in the atmosphere. The DIAL method uses a pulsed laser operating at two wavelengths, one strongly absorbed by the gas species of interest and one weakly absorbed
...

The pulse time and light absorption information from the return signals enables calculation of a gas concentration distribution along the length of the light path.

*Reference

Chambers et al. DIAL Measurements of Fugitive Emissions from Natural Gas Plants and the Comparison with Emission Factor Estimates. 15th Annual Emission Inventory Conference. 2006.

Here there is the pdf presentation.

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