Abstract
The aim of this study was to determine the positional accuracy of GeoEye-1 images and how it affects the delineation of the input prescription map (IPM) for site-specific strategies. Seven panchromatic and multi-spectral GeoEye-1 satellite images were taken over the LaVentilla village area (Andalusia, Spain), from April to October 2010, at an interval of approximately 3–4 weeks. Sixteen hard-edge ground control points (GCPs) were geo-referenced using a sub-decimetre DGPS. Each DGPS-GCP position was compared with the corresponding co-ordinates for each image to determine the position error (PE) and error direction angle ( $$ {\Upphi_{\text{ge}}}^{^\circ } $$ ). The PE and $$ {\Upphi_{\text{ge}}}^{^\circ } $$ for each GCP varied slightly for any given GeoEye-1 image and the overall PE among images estimated through the root mean square error (RMSE) varied considerably. RMSE ranged from approximately 2–9 m and from 3.5 to 9 m for the panchromatic and multi-spectral images studied, respectively, and the average was approximately 6.0 m for each of the series of images. Consequently, the geo-referencing of GeoEye-1 images is recommended to increase the positioning accuracy. Conventional geo-referencing using GCPs provided an average RMSE of 2 m for the panchromatic and 3.5 m for the multi-spectral images. The AUGEO System® geo-referencing of the 4-May GeoEye-1 image provided an RMSE of 0.75 m for the panchromatic and 2.70 ± 1.30 m for the multi-spectral images. The IPM delineated from remote-sensed images takes up the image geo-referencing error and, consequently, each micro-plot does not coincide with its corresponding ground-truth micro-plot. In this report, the percentage of non-overlapping area (%NOA) has been developed as a function of the PE/RMSE, α° (the angle between Φge and the operating direction, Φop), and the micro-plot size. The %NOA consistently increased as the RMSE and α° increased, and it decreased as the micro-plot width or length increased. The decision about micro-plot size should be based on the RMSE, α°, and the maximum admissible %NOA. In the case of the GeoEye-1 images studied with an average RMSE of 6 m, a micro-plot size of 6 × 30 m would have yielded an IPM inaccuracy (%NOA) of approximately 5 %, assuming an α° = 0°.
Highlights
Input prescription maps (IPMs) are a key tool for the implementation of site-specific management (SSM) strategies
The IPM delineated from remote-sensed images takes up the image geo-referencing error and, each micro-plot does not coincide with its corresponding ground-truth micro-plot
The position error (PE) and Uge for each ground control points (GCPs) varied slightly for any GeoEye-1 image and varied considerably between images taken on different dates (Table 1; data for each GCP not shown for abbreviation)
Summary
Input prescription maps (IPMs) are a key tool for the implementation of site-specific management (SSM) strategies. Each tiny rectangular plot fit the area covered by a nozzle or set of nozzles of the input application machinery, and could be named as ‘‘micro-plot’’ (Gomez-Candon et al 2011a). The size of the microplot varies widely, for example from approximately 1 9 2 to 10 9 30 m, with the microplot width (W) equal to, or a multiple of, the width covered by a nozzle of the application machinery, and the micro-plot length (L) normally a multiple of W. Mapping the biotic/ abiotic patch area to be treated and delineating the subsequent IPMs are critical for sitespecific strategies (SSM) implementation using remote-sensed images and, for practical reasons, both need to be matched (Ruiz et al 2006). By assessing Avena sterilis weed infestations through remote sensing and simulating micro-plots of diverse size, GomezCandon et al (2011b) estimated that the smaller the micro-plot area, the higher the environmental and economic benefits
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