Revista Brasileira de Cartografia (Apr 2005)
Direct expansion in the estimate of agricultural cultures by regular segments
Abstract
The objective of this work was to develop a method to estimate the crop area of coffee, maize and soybean in the region of Cornélio Procópio, Paraná State, Brazil. This region comprises a total of 23 municipalities. The direct expansion method with regular segments of 1 km x 1 km was used to estimate the crop area. The stratification was carried out with remote sensing satellite images, digital image classification procedure, Geographic Information System (GIS), GPS (Global Positioning System) among others. The sampled area was 1.26% of the region which corresponds to 89 segments. These segments were visited during a field work from October 29th to December 10th of 2002. Comparison between the results of this research and the official estimates indicated that best results were obtained for soybean area estimation, which occupies 32.1% of the region. The soybean area estimation had a difference of 5.9% in relation to the official estimate and a coefficient of variation equal to 6.6%. The result was available one week after the end of the field work indicating that the method is fast. The conclusions of the work are: 1) the thematic map of the images makes it possible to stratify the region and can also be helpful to the subjective surveys; 2) the regular segments were easily located in the field, with the use of the GPS; 3) the crop area estimation was fast and met the opportunity criteria; 4) an error figure is associated to the estimates, attending the reliability criteria and; 5) the errors of the estimates varied in response to the cultivated area by each crop in the region.
