Crop Agriculture

Landsat 8 SR Tutorial w/ Imagery Download

Updated GIS AG MAPS Image-Based DOS Surface Reflectance (SR) Methods: Revised & Simplified

Related Pages: Relative Scatter Calculator    Landsat 8 / Sentinel-2 Rare Comparison & Data Download

 

Landsat surface reflectance (SR) 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. The USGS Landsat 8 SR Algorithm is not a dark object subtraction (DOS; Chavez, 1988) method and takes into account many more factors than DOS, though DOS has been applied extensively for decades. If you plan on using both Landsat 8 and Sentinel-2 (as we feel you should), we recommend using the GIS Ag Maps Landsat 8 and Sentinel-2 DOS Methods with the Relative Scatter Calculator, because conversion to SR is based on the same principles. You can simply open the Data Sources folder, click the USGS GloVis "Next" link, 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. After converting to SR, you can easily calculate indices, such as NDVI or MSAVI for vegetation health or NDWI for vegetation dryness, and many others. Contact us if you have any questions about applying the imagery.

GIS Ag Maps offers a simple and fast dark-object subtraction (DOS; Chavez [1988]) 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.