Landsat 8 & Sentinel-2 Corn LAI & Yield Calculators
(CALCULATORS ARE BELOW TEST; MAY TAKE A FEW MOMENTS FOR CALCULATORS TO APPEAR)
Information and free software to use the calculator can all be acquired or accessed from this website. Imagery is free and can be downloaded from the Free Satellite Imagery link on the top menu. Landsat 8 and Sentinel-2 imagery can be downloaded in surface reflectance x 10,000 format (need to divide imagery by 10,000 to convert to surface reflectance units; for example, if pixel value is 314, surface reflectance is 0.0314). Imagery in digital number format can be converted to surface reflectance by following the surface reflectance tutorials on this website. To use the calculators, simply open GIS software (free QGIS, ArcGIS, or another), add Landsat 8 or Sentinel-2 surface reflectance imagery, click pixels in a field to view surface reflectance values, and enter the values in the calculator/s below.
Corn Calculators
Corn LAI and yield can be calculated for Landsat 8 and Sentinel-2 imagery. LAI can be calculated for times during the season from when the field average LAI is about 1.0 through the R-stages (to estimte a field average LAI 1.0, calculate LAI for pixels throughout a field until you feel you can approximate a field average). Corn yield can be estimate for imagery during the the R3-R4 stages (yield will be low if using imagery after R4). The "earlier" calculator LAI value should be used from LAI 1.0 to later V-stages. Switch to the "later" calculator LAI value when the "later" value is within 0.25 to 0.50 LAI of the "earlier" value. This happens in a normal to good season during the later V-stages; during a bad season however, the "earlier" value may end up being used for the whole season (in other words, the "later" value may always be at least 0.50 LAI less than the "earlier" value). The yield amount is a function of the "later" LAi value, if the "earlier" value is used for the whole season, enter the "earlier" value in the "later" value cell to calculate a yield amount. Once again, only use the yield prediction value when imagery represents R3-R4 growth stages.
Aim to have LAI at or above the irrigated or rainfed LAI line on the chart below (Nguy-Robertson et al, 2005)
Landsat 8 Calculator
(MAY TAKE A FEW MOMENTS FOR CALCULATOR TO APPEAR)
Enter Landsat 8 corn pixel surface reflectance below: "Earlier" LAI requires just Band 4 (Red) and Band 5 (NIR) values; "Later" LAI requires Band 3 (Green), Band 4 (Red), and Band 5 (NIR) values. (To compare LAI values to determine if "Earlier" or "Later" LAI should be used, all values must be entered):
Embedded Excel Calculator (Click Cell and Enter Value). MAY NOT BE VIEWABLE IF USING PHONE.
Sentinel-2 Calculator
(MAY TAKE A FEW MOMENTS FOR CALCULATOR TO APPEAR)
Enter Sentinel-2 corn pixel surface reflectance below: "Earlier" LAI requires Band 4 (Red), Band 5 (Red Edge), Band 7 (Red Edge), and Band 8a (NIR) values; "Later" LAI requires just Band 3 (Green), Band 4 (Red), and Band 8a (NIR) values. (To compare LAI values to determine if "earlier" or "later" LAI should be used, all values must be entered):
Embedded Excel Calculator (Click Cell and Enter Value). MAY NOT BE VIEWABLE IF USING PHONE.
Reference
Nguy-Robertson, A., Gitelson, A., Peng, Y., Viña, A., Arkebauer, T., and Donald Rundquist. 2012. Green leaf area estimation in maize and soybean: combining indices to achieve maximal sensitivity. Agronomy Journal 104:1336–1347 (2012)