Estimation of papaya volume and surface area using a dual ellipsoid representation and image analysis

Estimation of papaya volume and surface area using a dual ellipsoid representation and image analysis

Knowledge of volume (V) and surface area (A) of agricultural products can be used in the design of machinery, in predicting amounts of pesticides, and in quantification of bruise, abrasion, and insect damage. A and V are also valuable for calculating rates of post-harvest loss in horticultural produce and monitoring fruit growth. In this study, laser scanning methods and standard hydro-static techniques are in first place used to create accurate and scaled 3D models of a fruit cultivar (i.e. red papaya, Carica Papaya) of different dimensions. Based on these models a geometric representation for a rapid estimation of V and A of a given papaya is presented. In essence, this representation relates to a mathematical function based on a 3D shape formed by two halves of ellipsoids that have separate radius dimensions. This representation will be referred to as dual ellipsoid for the remaining of this manuscript.

Statistical data regarding V and A as obtained via the proposed dual ellipsoid is determined by comparing said data with that obtained from the above mentioned hydrostatic and laser scanning techniques. Results show that for the relatively large papaya samples considered, the predicted (via the proposed representation) and the 'true' figures for V and A agree within 1.8% and 2.0 % respectively.

The model representation is defined by fruit dimensions which comply with Australian standards for size and volume characteristics of papaya cultivars in general, that is, papaya axial dimensions such as width and length. In this work these axial dimensions are derived from measurements taken on scaled digital images of the fruit using an open source digital image analysis software. Hence, the proposed model may constitute a practical, effective and economic tool for many applications related to field measurement, mapping, growth, monitoring, harvesting, processing, storing and handling of this highly perishable fruit.

In particular it may lead to applications in farm management, production and forecasting. For example, many present practices related to monitoring of fruit growth in the field are still relying on callipers and/or measuring gauges. In this context, a GIS (Geographical Information Systems) field measuring scheme is suggested, capable of storing pictorial information of papayas, including attributes like location (i.e. latitude and longitude) of measurements, weather and time of measurements.

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