Visual measurement of the number of direct-seeded paddy rice [Oryza sativa] seedlings using a digital still camera
2007
Okado, M(Ishikawa Prefectural Univ., Nonoichi (Japan))
In recent years, digital still cameras have come to be widely used. This study provides an example of the use of digital still cameras for agriculture. Five students observed establishment images of direct-seeded paddy rice on the display unit of a personal computer, and the number of seedlings was measured. Image features that affected the measurement error rate and the measurement time were examined by statistical analyses. In this study the following image features were identified as potentially significant: image resolution; the number of seedlings; the reflection of seedlings from the water surface; and the overlap of seedlings. In 86.8% of the visual measurements the number of seedlings measured was fewer than the actual number. Male students, in particular, tended to underestimate the number of seedlings. Using the stepwise method to analyze the data revealed that image resolution, the number of seedlings, and the overlap of seedlings influence the measurement error rate. It was estimated that the measurement error rate became 4.7-13.0% when the number of seedlings was 40-70/square m, the recommended plant density at transplanting for Ishikawa Prefecture. It was considered that number of seedlings and reflections of the seedling from the surface of the paddy water influenced the measurement time. Moreover, there were no correlations between the measurement time and the measurement error rate.
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