For Tucumán province in Argentina, citrus crops have great economic and social importance. Tucumán is the biggest producer of lemon in the world, with around 40,000 ha of citrus farms.
In addition, Tucumán province supplies potatoes for more than 50 percent of national consumption. Due to the importance of these crops for the province, it was fundamental to have precise information of the planted area, in little time and with low cost. Remote sensing (RS) technology allowed to obtain information about agricultural data. Due to multispectral characteristic of the technology, there were less human errors and costs as well.
Estación Experimental Agroindustrial “Obispo Colombres”(EEAOC) is an autarchic institution of the Tucumán province government. It was set up to provide solutions to the different problems existing in both agricultural and livestock provincial activities and their associated industries by means of research and technology development.
Since 1997, Tucumán Province has been using digital information from Landsat TM and ETM+ satellite imagery and generating a very important database for the regional economy.
During this period, problems arose with citrus crops’ classification, fundamentally associated with the spatial resolution of Landsat images. To solve these problems, auxiliary information was used using air pictures and CBERS IIb HRC images (Brazilian satellite).
Spatial resolution is very important in image interpretation because it intervenes at the detailed level. It is directly related with the work scale and the reliability obtained in the interpretation. In terms of spectral resolution, a sensor will be as much suitable as the number of bands.Radiometric resolution indicates the sensor capacity to detect variations in the energy received. It is identified with the value range that the sensor codes. The bigger the radiometric resolution, the better will be the image interpretation.
The launch of WorldView-2 satellite provided a new perspective to estimate crops planted areas. WorldView-2, with 8-band multispectral commercial imagery, provided more spatial, spectral and radiometric resolution in comparison to other satellites. This satellite is equipped with the Red Edge and Yellow bands that are specifically designed to detect key vegetative phenomena. The Red Edge band marks the transition between where plant pigments absorb visible light and reflect infrared light. Its position varies and shifts according to changes in plants’ health, age and growth rate. Similarly, the Yellow band can detect changes in the amount of chlorophyll in leaves.