Landsat Surface Reflectance from Earth Explorer and Albedo

[jake]

Hello,

I'm pretty green when it comes to RS and I'm doing this school project that I need help with. The project is to measure albedo changes for the tongue of a glacier and I'm using R programming to do it. So I got my data from earth explorer and went for the surface reflectance product in order to save some steps. However, the values for these cells are higher than expected, around 2000 depending on the band. I say higher because when I use a weighted average formula for calculating albedo, which I found in some papers cited below, the outcome gives me cell values of around 1000, not the 0 to 1 I would expect for and albedo. The paper mentions its using a surface reflectance as well for this formula. 

My question is, is this formula wrong? Albedo = 0.493Band2 + 0.203 Band + 0.150 Band5 + 0.154Band

Or does some other processing need to be done to my Earth Explorer Surface Reflectance Product. https://landsat.usgs.gov/landsat-surface-reflectance-high-level-data-products

Also I'm using Landsat 4-7 images. 

 

sources:

Pimentel, Rafael, et al. "Comparison between Snow Albedo Obtained from Landsat TM, ETM+ Imagery and the SPOT VEGETATION Albedo Product in a Mediterranean Mountainous Site." Hydrology 3.1 (2016): 10.

Also, this is really similar but uses TOA instead of surface reflectance

http://yceo.yale.edu/how-convert-landsat-dns-albedo

Any help is appreciated

 

Jake

[mamadouba]

The surface reflectance products have a scale factor of 0.0001.  For example, a value of 1000 is actually 0.10.  Rescale the data first or rescale your formula coefficients, either way works.

[zabdi3l]

ENVI and USGS GeoTIFF with Metadata format data

The USGS now provides data in the GeoTIFF with Metadata format.  ENVI software can easily convert the optical band data to ToA reflectance values when you open the USGS file that ends with “_MTL.TXT”.  ENVI will automatically open the Landsat image as multiple files with the 6 or 7 bands of optical data as one of several files.

To create a reflectance data file using ENVI Classic, from the ENVI main menu bar select Basic Tools |Preprocessing |Calibration Utilities |Landsat Calibration.  Select the optical data file (it has six or seven bands) and the ENVI Landsat Calibration dialog should open with all of the calibration parameters filled in.  Click on the Reflectance radio button and enter an output file name.

For ENVI Standard, select from the Toolbox | Radiometric Correction | Radiometric Calibration.  Select the optical data file and the Radiometric Calibration dialog opens.  Under Calibration Type choose Reflectance and save the new file.  As a reminder, reflectance values range from 0.0 to 1.0 and are stored in floating point data format.

[mamadouba]

zabdi3l, jake stated that the imagery was sourced from the Earth Explorer Surface Reflectance Product; therefore, the data are already calibrated and atmospherically corrected to surface reflectance using LEDAPS (Landsat 4-7).  There is no need to calibrate in ENVI, or any other software.  However, the data do have a scale factor of 0.0001 which must be taken into consideration and applied if you want to convert data from 16-bit integer back to floating point..