Monday, December 21, 2009

Foolishness of the Masses - Completed KMeans

The urge to automate everything can be powerful (sudo make me sandwich) , often this leads to strange errors. Google trusts the wisdom of the masses and uses it to build a spell checker, nice instance of learning, but still automation. Sometimes the mass gets it wrong and Google follows suit. Today it threw a "did you mean ambiguus" in my face. Nevertheless ask the audience is always the first lifeline used - I haven't found clear statistics of lifeline usage by asking Google yet (so Google is not completely capturing the wisdom of the masses - have we stopped answering questions and started asking too many ?).

The problem of image classification which I have discussed in the past brings a similar dilemma, it is a question with unclear answers - which area of the image belongs to which class ? We can use supervised learning (capturing the wisdom of the expert) or we can let algorithms spot groups in the data (automation). In the end balance is needed between the two to produce "usable" results. The last OTB-QGIS plugin now implements one of the classic unsupervised classifiers - KMeans. I tried it out on the same landsat image as the one with SVM , the results are quite different.

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