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Title: DETECTING MARIJUANA USING OPTICAL REMOTE SENSING

Author
item Walthall, Charles
item Daughtry, Craig

Submitted to: Proceedings of ONDCP International Technology Symposium
Publication Type: Proceedings
Publication Acceptance Date: 6/5/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Development of an optical wavelength remote sensing system to detect illicit marijuana cultivation would greatly assist law enforcement agencies. If seeking to detect the plants themselves, this would require the identification of a unique spectral reflectance characteristic of marijuana or sufficient differences between the spectral reflectance of marijuana and other plants. Other considerations include how remote sensing of vegetation must deal with the constantly changing reflectance of plants as they grow, changes across a landscape of background (soil, plant litter, etc.) reflectance that affect plant canopy reflectance, relatively small spectral differences between different plant species, variations in reflectance from changing sun and view angles, atmospheric haze effects on viewing and a lack of inexpensive, reliable detectors that are sensitive to the required wavelengths. Analysis of marijuana and other plant species leaf reflectance indicates that a small amount of contrast in the visible, near infrared and short-wave infrared wavelengths exists. However, characterization of the variability of signatures among marijuana varieties and for different stages of growth are still needed to definitively define marijuana leaf spectral reflectance signatures. Successful detection of marijuana cultivation may ultimately require different types of sensors to not-only detect the plants, but also signs of cultivation or modification of the landscape by man for marijuana cultivation.

Technical Abstract: Development of an optical wavelength remote sensing system to detect illicit marijuana cultivation would greatly assist law enforcement agencies. The complexity of reflectance from the soil-plant-atmosphere system creates many impediments to the development of such a system. Remote sensing of vegetation must deal with the dynamic nature of the optics and morphology of plant growth, the effects of background reflectance on plant canopy reflectance, relatively low spectral contrast between different vegetation canopies, variations from the bidirectional reflectance distribution function, atmospheric effects and limitations of technology. Analysis of marijuana and other plant species leaf reflectance, which dominates the reflectance of full plant canopies, indicates contrast in the visible and near infrared and short-wave infrared wavelengths. Characterization of the variability of signatures among marijuana varieties and for different stages of growth of canopies are still needed to definitively define marijuana leaf spectral reflectance signatures. Successful detection of marijuana cultivation may ultimately require different types of sensors to not-only detect the plants, but also signs of cultivation or modification of the landscape by man for marijuana cultivation.