Crops from space
In order to ensure a good and consistent supply of food it is very important that countries and regions know how much harvest a particular area will produce. PhD student Mobushir Riaz Khan at the University of Twente’s ITC Faculty has developed a method for using satellite images to determine which crops are cultivated where. A second method then estimates how much harvest that given area is likely to yield, so far at an accuracy of 95 per cent. He defended the dissertation based on this research on Wednesday, 23 February at the ITC Faculty.
From the perspective of food safety, for the allocation of agricultural subsidies and to make the best possible use of available agricultural land it is vital that policymakers can estimate which crops grow in a certain area and how much harvest they will yield. For a large area it is usually difficult, time-consuming and therefore expensive to determine such matters. With this in mind, Mobushir Riaz Khan of the Faculty of ITC at the University of Twente developed a method by using satellite images to provide accurate estimates on which crops grow where, in what quantities and how much can be harvested per hectare. The method can benefit poorer countries as well as wealthier countries, as the satellite images used are freely available.
The first stage of the study focused on identifying for agricultural land through the use of satellite images (hypertemporal SPOT-Vegetation NDVI images) the area fractions of crop types grown. The results were then validated using a large amount of field data. It turns out that the method provides an accurate reflection of the situation on the ground. For example it showed that a much smaller surface area was being used for the cultivation of sunflowers in the Spanish region of Andalusia than had been registered with the European Union (which subsidizes the cultivation of sunflowers). Collaboration with the Andalucian policymakers aims to improve the quality of their reporting, to remove bias, and to present their statistics also as cropmaps.
In the second phase of his doctoral research, Mobushir Riaz Khan developed a method to accurately estimate achieved yield levels for the relevant areas. His method was based solely on the use of satellite images with information on canopy temperature and a prototype crop growth model. This method made it possible to estimate wheat yields at a one square kilometre scale to an accuracy of 95 percent. Additional validation test however remain required.
A survey has revealed that the vast majority of professionals who work with agricultural maps see added value in the new method and are interested in using it. Khan and other researchers at the ITC Faculty will develop the method to further increase its accuracy and apply it for a wider range of crop types.
Mobushir Riaz Khan
Mobushir Riaz Khan carried out his doctorate research at ITC, the Faculty of Geo-Information Sciences and Earth Observation at the University of Twente. He was supervised by Professor Eric Smaling and Dr Kees de Bie.
Note to the press: For more information or to receive a digital version of the dissertation Crops from Space: Improved Earth Observation capacity to map crop areas and to quantify production, click here or contact Joost Bruysters (+31 (0)53 489 2773 / +31 (0)6 1048 8228).