The aim of the research was to clarify the pre-processing steps required for satellite images before starting to analyze and extract data from them using the ENVI program. Radiometric and topographic correction applied to the Landsat image 2017, and then we calculated the NDVI index for this image before and after applying pre-processing. The results showed a difference in the spectral values of the image before and after the radiometric correction, especially in near infrared band. The reflection values were recorded in the original image between (40-50) and (300-3500) in the corrected image. The difference in the reflection values after the topographical correction was also visible on the near- infrared and infrared bands, especially in the points where shadows of the terrain. Differences in the values of NDVI for 2017 were observed before and after the application of pre-processing on the image, especially in points of good and very good vegetation coverage with high values of the index. The study concluded that it is important to follow the minimum number of steps required for preprocessing steps in order to avoid unnecessary steps and recommend well tested, readily available, and adequately documented data approaches and data products.