Browsing by Subject "Unkrautartenerkennung"

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Teilschlagspezifische Unkrautbekämpfung durch raumbezogene Bildverarbeitung im Offline- und (Online-) Verfahren (TURBO)
(2006) Oebel, Horst; Gerhards, Roland
Georeferenced application maps (TURBO) is presented. The system was applied and analysed on agricultural fields from 2004 to 2005. The results can be summarized as followed: For online image acquisition bi-spectral cameras were developed which took homogeneous grey scale pictures with a strong contrast using a combination of two spectral channels in the near infrared and the visible spectrum. Three bi-spectral cameras were mounted in front of a prototype carrier vehicle. Using an automatic control of the exposure time, well focused pictures of weeds in cereals, maize, sugar beets, peas and oil seed rape were taken at a speed up to 10 km/h and stored together with their GPS coordinates. Under changing light conditions, bi-spectral images were free of faults. Stones, mulch and soil were not illustrated. The picture quality showed a clear improvement compared to current image analysis technologies using colour and infrared cameras in plant production. The geometric resolution of the cameras was sufficient for creating application maps. With a size of 0.014 m² per picture weed seedlings were representatively assessed. The dense grid of 3.500 sampling points per hectare allowed an efficient detection of weed distribution within agricultural fields. The procedure of shape analysis allowed precise identification of weed species in a speed of 20 images per second. The classification rate of unclassified plants using Fuzzy Logic or the principle of minimum distance was between 73 % (malt barley) and 85 % (oil seed rape). The calculation of discrimination functions to separate crops and weed classes by shape parameters allowed a better classification of unknown plants and increased the classification rate to 88.4 % (sugar beets) and 94 % (malt barley). Characteristic shape features of 45 weed species in the growth stages BBCH 10 to BBCH 14 were stored in a database and the classification of weed species in malt barley, maize and sugar beets was studied using discrimination analysis. In growth stage BBCH 10 weed species could be differentiated on average by 70 %. Crops were accurately differentiated from broadleaved weeds and grass weeds. Joining weeds species (BBCH 10) in the classes broadleaved weed species, grass weeds, Galium aparine and crop resulted in correct classification of 83 % in malt barley to 96 % in maize. With manual, GIS-based and image analysis sampling methods treatment maps for three weed species classes were created for site-specific weed control in cereals, sugar beet, maize, oil seed rape and peas on a total of 138 ha. Economic weed threshold were used as a decision rule for chemical weed control. Herbicides were only applied when the economic weed threshold was exceeded. Above the economic weed threshold the herbicide dosage was varied from 70 % to 100 % depending on the density of weed species. Herbicide application was performed with a newly developed multiple sprayer. The sprayer integrates three conventional sprayers on one machine including three separated hydraulic circuits, boom section control (3 m), dGPS for real time location and a central control unit. During application the on-board computer loading a georeferenced application maps was linked to the spray control system for precise application of up to three different herbicide mixtures. Herbicide savings using site-specific weed control depended on the cultivated crop, weed species composition and weed infestation levels. On average 47 % of herbicides for grass weeds and 35 % for broad-leaved weeds were saved. Herbicide use to control Galium aparine and Cirsium arvense was reduced by 71 %. The efficacy of site-specific weed control was documented by manual weed sampling before and after post emergent herbicide treatments. It ranged from 71.8 % to 98.8 %. Weed infestation level did not increase in the following crops. First results with yield mapping of experimental fields revealed that site-specific weed control did not cause yield reduction. On contrary, in cereals higher yields were observed at locations where no herbicides were applied. However, further studies are needed to prove this hypothesis. The economic evaluation of site-specific weed control over two years on practical farm sites showed that site-specific weed control was profitable. The average savings for herbicides were 27.61 ?/ha. This resulted in an average profit of 11.35 ?/ha using the system for site-specific weed control.