Updated Landsat 8 Reflectance Tutorial w/ Imagery
GIS AG MAPS Image-Based DOS Surface Reflectance (SR) Method: Revised & Simplified
Landsat surface reflectance is available for free from the USGS, though converting to surface reflectance independently can be beneficial; for example, surface reflectance may not available for a particular scene or may be needed as soon as possible. You can simply open the Data Sources folder, click the USGS GloVis link (Chrome will not work; Mozilla will work), download free Landsat 8 imagery (need to create a password if you do not already have one), and covert the imagery to surface reflectance based on the steps in the Tutorial. GIS Ag Maps offers a simple and fast dark-object subtraction (DOS; Chavez ) method. Results published in Remote Sensing of Environment based on using GIS Ag Maps DOS SR for NDVI can be viewed here. IMPORTANT: This Landsat 8 DOS method has only been tested for accuracy for solar elevations greater than 50 degrees - we have found that visible band values become much less accurate at solar elevations less than 30 degrees, but have not completed research for elevations from 30 to 50 degrees. Therefore, as of now, this method should not be applied to retrieve visible band surface reflectance when solar elevations are less than 50 degrees.