Thursday, 13 September 2012

Automating Crop Surveillance – theory vs. praxis - part 2/3

The Science behind

To automate some of the expert processes we leverage some of the latest computer vision and machine learning techniques and apply them to three specific tasks in this survey.

1. Automated diagnosis

The objective here is to assess the feasibility of automated computer vision based diagnosis of CMD. Feature extraction techniques based on color and shape are used to extract features from the images of the healthy and CMD-infected cassava plants and classification using a set of standard classification methods (naive Bayes, two-layer MLP networks, support vector machines, k-nearest neighbor and divergence- based learning vector quantization) is applied to determine the diagnosis of the plant(image).  This diagnosis is either done at the server end or on the phone.
Depiction of survey process - (a) Image capture, (b) Automated diagnosis, (c) Real-time mapping

2. Automated whitefly count

Whiteflies are the major vector responsible for transmission of cassava mosaic disease and other cassava related diseases. To understand the spread of disease, experts are required to count the number of whiteflies on a leaf. This however is not a trivial task; the small size and volatility of the whiteflies results in inaccurate whitefly counts. We implemented a computer vision-based system on the mobile phone that automatically counts the whiteflies on a leaf from a photograph taken of the leaf or a video of the leaf image taken in real time.

Whitefly detection and counting

3. Determination of level of necrosis in diseased roots

For some Cassava Brown Streak Disease (CBSD) the major part affected is the tuber/root of the plant. Experts out in the field ordinarily dig up a set of plants in selected gardens and examine five cross-section cuttings of the root. A score of severity of disease is assigned to the plant based on the average percentage of necrotized root of all five cross-sections examined. We intend to automate this process so there is a uniform scoring of necrosis from a uniform system.

Necrotized roots infected with CBSD

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