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Title: DETERMINATION OF EARLY STAGE CORN PLANT HEIGHT USING STEREO VISION

Author
item SHRESTHA, D - IA STATE UNIV
item STEWARD, B - IA STATE UNIV
item Kaspar, Thomas

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/17/2002
Publication Date: 7/17/2002
Citation: SHRESTHA, D.S., STEWARD, B.L., KASPAR, T.C. DETERMINATION OF EARLY STAGE CORN PLANT HEIGHT USING STEREO VISION. INTERNATIONAL CONFERENCE ON PRECISION AGRICULTURE ABSTRACTS & PROCEEDINGS. 2002. CD-ROM. MADISON, WI.

Interpretive Summary: A major limitation to identifying and mapping yield-limiting factors in agricultural fields is the availability of appropriate on-the-go sensing technologies for plant growth during the growing season. The ability to map crop height and changes in crop height over time in agricultural fields would be a useful diagnostic tool to identify where and when crop stress is occurring. Additionally, plant height or rate of plant height change could be used to evaluate spatial crop response to inputs of fertilizers, herbicides, or insecticides. In this study we developed and tested a prototype image acquisition and analysis system for measuring crop height. With further development this system will be capable of measuring and mapping crop height on-the-go from a tractor-mounted platform. Farmers should be able to use this system to identify areas in their fields that are stressed and require management inputs such as fertilizer or water areas that did not respond to inputs applied earlier such as fertilizers, herbicides, or insecticides. In general, farmers will use this information to increase profitability and reduce environmental impacts. Scientists will use this system to identify the causes of variable crop growth in fields and to find management solutions to alleviate spatially variable crop stress.

Technical Abstract: The ability to map crop height and changes in crop height over time in agricultural fields would be a useful diagnostic tool to identify where and when crop stress is occurring. Additionally, plant height or rate of plant height change could be used to evaluate spatial crop response to inputs of fertilizers, herbicides, or insecticides. Periodic measurements of plant height could be used to calculate growth rate and have potential for characterizing spatial variation of plant response to inputs and field conditions. A corn plant height measurement system using stereo machine vision was developed. A test apparatus was developed, which consisted of an x-y translating sensor platform with a CCD camera and an imaging stage for camera calibration and plant image acquisition. The position of the camera was controlled precisely by a microcontroller and allowed images to be taken of the top view of the plant from a canonical stereo configuration. Corresponding plant edge points in two images were found using an area-matching algorithm after plant object segmentation. Plant height was estimated by triangulation using pixel disparity between two images. Average plant height was compared to manual measurement of maximum plant height. The stereo vision system estimated maximum plant height with a RMSE of 2.55 cm. Sources of error were investigated. These results demonstrate the potential of stereo vision for a vehicle-mounted crop height measurement system. Farmers will use this information to increase profitability and to reduce environmental impacts. Scientists will use this system to identify the causes of variable crop growth in fields and to find management solutions to alleviate spatially variable crop stress.