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Evaluation of Plant Area Index measurements over crops using hemispherical images

Evaluation of Plant Area Index measurements over crops using hemispherical images. Sylvie DUTHOIT, Valérie DEMAREZ CESBIO. Study area. LMA for each species. DESTRUCTIVE MEASUREMENTS. 2004 : Planimetric technique Random selection of 10 plants (at least).

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Evaluation of Plant Area Index measurements over crops using hemispherical images

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  1. Evaluation of Plant Area Index measurements over crops using hemispherical images Sylvie DUTHOIT, Valérie DEMAREZ CESBIO

  2. Study area

  3. LMA for each species DESTRUCTIVE MEASUREMENTS • 2004 : Planimetrictechnique • Random selection of 10 plants (at least). • Removing of the totality of the green leaves of each plant. • Measurement of the mean green leaf area by plant with a scanning planimeter (Li-Cor 3100). • Estimation of the mean stem area for sunflowers and corn (height and diameter). • Estimation of the mean PAI from the plants density of the field.

  4. Leaf Mass Area for each crop

  5. Wheat 2005, in progress… • Gravimetrictechnique • - 8 50x50cm squares are removed • - Measurement of the green leaf and stem area of a sub-sample • - The totality of the sample is dried at 65°C • The Leaf Mass Area of the sub-sample is calculated • The PAI of the total 50x50 cm is calculated from the sub-sample LMA. Test by scanning the totality of the sample for the 2 first measurements

  6. RESULTS Evolution of the PAI during the growing season

  7. HEMISPHERICALPICTURES Nikon Coolpix 4500 Fisheye 21x - Transects of 20 images for each date (except for the wheat parcel) - One picture every 10 meters - One between the rows, one under the row. - From above or below the canopy, depending on its height

  8. Classification process Mean gap fraction CAN_EYE PROCESSING Optical center Considered field of view : 60° 12 images at the same time

  9. COMPARISON Destructive PAI measurements -PAI from CAN_eye software

  10. Canopy structure • Corn : big green leaves easy to classify. • Sunflowers : dry leaves and flowers, more difficult. • Soya: low canopy, very dense with planophyl leaves distribution saturation effect?? • Wheat: little and thin leaves, problem of the resolution Distance from the canopy For wheat, comparison between images at 30 cm and 60cm from canopy. processing at 60 cm gives best results. « USER » CONCLUSIONS Downward-upward looking images Prefer upward looking images when possible. • Illuminationconditions • Classification easier by completely cloudy sky. • avoid sunny conditions, particularly when taking downward images.

  11. RESULTS True PAI

  12. THANK YOU…

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