* COMPLETE THESE STEPS TO GET UP AND RUNNING WITH FREE SATELLITE IMAGERY *
Step to Understand & Use Landsat 8 & Sentinel-2 Imagery for Free - No Experience Necessary
GIS Ag Maps has about 200 pages of information, so we made the steps below (links to pages) in order to easily start using satellite imagery with free GIS software. All steps are links are to pages on this website.
1) Download Free QGIS (geographic information systems software). It is necessary to have proper software to open, process, and apply satellite imagery. Make sure to also download the OpenLayers Plugin and 7-Zip extraction software (if needed). See Course 1A if you need help downloading and installing software.
2) Learn about atmospheric scatter and correction. Prior to using satellite imagery, it is important to understand how atmospheric conditions affect satellite imagery and the difference between digital number radiance, top of atmosphere (TOA) reflectance, and surface reflectance. It is also important understand different image-based dark object subtraction (DOS) atmospheric correction methods. Make sure to click the links to access the necessary information.
3) Access the Landsat 8 (L8) & Sentinel-2 (S2) Comparison page. You should find out the differences between the two satellites and corresponding imagery, which are significant, prior to working with the imagery.
4) Complete the QGIS Landsat 8 Conversion to Surface Reflectance Tutorial (which is also Course 2A). You now start to use Landsat 8 imagery, downloading it from this website by clicking the link near the top pf tutorial that says "IMAGERY FOR THIS TUTORIAL CAN BE DOWNLOADED HERE". Complete the tutorial, applying the recommended Bin5 -.008 method for starting red band scatter and use that red band scatter value to calculate relative scatter for the other bands (you will understand this when you get to this point).
5) Complete the QGIS Sentinel-2 Conversion to Surface Reflectance Tutorial (which is also Course 2B). You now start to use Sentinel-2 imagery. Complete the tutorial, applying the recommended Base of the Histogram - .008 method for starting red band scatter and use that red band scatter value to calculate relative scatter for the other bands (you will understand this when you get to this point).
6) Download Rare Landsat 8 & Sentinel-2 Imagery Comparison. Open the layers in QGIS. This will enable you to view a comparison between Landsat 8 & Sentinel-2 imaged on the same date and location at virtually the same time.
7) View the "Why Apply NIR to Crops & Other Vegetation Page". Whether or not you are planning on using satellite imagery for vegetation, it is helpful to understand vegetation for many different purposes and it is helpful to understand that satellite data can be applied in the non-visible part of the spectrum.
8) Complete Course 3A: Downloading & Applying Imagery to Crops in QGIS. This course in not only for people who are interested in crops, but is also for those who would like to start downloading and applying Sentinel-2 imagery in general. It emphasizes downloading imagery yourself from the Sentinel-2 source for your area of interest. This course contains important simple symbology techniques to assess crop condition that can be applied to other surfaces.
9) Complete Course 2C: Calculating Spectral Indices from Satellite Imagery for Free. This course shows you how to use the raster calculator in QGIS to calculate vegetation spectral indices (such as NDVI), and also covers wildfire and snow indices.