ASSESSMENT OF EFFECTS OF HURRICANE EMILY ON MAIZE PRODUCTION IN YUCATAN, MEXICO, USING FIELD DATA AND AERIAL IMAGERY IN A GIS ENVIRONMENT

摘要

The hurricane "Emily" hit the Mexican state of Yucatan on 17 and 18 of July 2005 with sustained winds of 145 km/hr. Ten days after its presence, an assessment of damages was made by applying 3 strategies: to collect field data, to collect aerial data and incorporate them in a GIS environment. 23 municipalities of Yucatán that were in the route of "Emily", with a total agricultural area of 209 876 ha, were estimated. For the field stage, 58 production units were characterized. The field data included GPS coordinates of each production unit, a plot of its spatial relationship, the categorization of the damage in terms of dead/live plants rate, the vegetative or phenological stage of maize and photographs of the crop taken with a digital camera. For the aerial stage, the Terrahawk~(? )Aerial Imaging System was used. The aerial data collected during 3 flight missions on July 27, 29 and 30 included 267 high resolution aerial images of the affected agricultural areas. All the images were geometrically corrected using a highways vector file as first option and orthophotos as second option as reference frame. Both field and aerial data were set in a database structure for incorporating to a GIS environment. The assessment focused on effects on production volume (ton) instead of area (ha) because the image coverage was not complete due to the malfunctioning of the imaging system. The data analysis indicates that the diminution in maize yield was in the order of 3 848 ton of grain, and plant growth rate was recovered in most of the maize areas in the 50 km route of Emily.