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# Cape Cod Bay Watch Landsat Tutorial notes 7/14/14

This is a revision from July 26, 2014 15:36. View all revisions

These are the notes from a tutorial that Ned Horning gave to the members of Cape Cod Bay Watch and the Jones River Watershed Association, (Pine duBois, Alex Mansfield, Karen Vale, and Adam Augello) and Don Blaire from Public Lab, on how to download and edit GeoTIFF Landsat images on QGIS. Cape Cod Bay Watch and the JRWA want to use this program for thermal mapping of Cape Cod Bay, specifically to measure the thermal plume generated from the Pilgrim Nuclear Power Station in Plymouth.

Website: glovis.usgs.gov

-must have Java 7 or older to run program -won’t work on Google Chrome if you have a Mac

Steps below use Pilgrim Nuclear Power Station in Plymouth, MA as an example:

DN is the pixel values in the image.

Here is the formula that I used in QGIS Raster Calculator: "LC80120312014173LGN00_B10@1" * 0.0003342 + 0.1

You would replace "LC80120312014173LGN00_B10@1" with your image.

To calculate brightness temperature use this equation:

T = K2_CONSTANT_BAND_10 / (ln((K1_CONSTANT_BAND_10 / TOA Radiance) + 1))

If you want to combine both of these so you only have to run it once the equation is: T = K2_CONSTANT_BAND_10 / (ln((K1_CONSTANT_BAND_10 / (DN * RADIANCE_MULT_BAND_10 + RADIANCE_ADD_BAND_10)) + 1))

Here is the formula that should work in the QGIS Raster Calculator but it doesn't since it appears that the natural logarithm, "ln", isn't supported yet in this new version of the raster calculator. The user guide mentions that it will be supported in a future release.

• 1321.08 / ln(774.89 / ("LC80120312014173LGN00_B10@1" * 0.0003342 + 0.1) + 1)

I'm not sure of the best way for you to calculate brightness temperature since this isn't working at this time. The problem is that there are several options and they all require using another software package. One option that might be useful would be to do the processing using an R script. I could write a script that would require you to enter the image directory path and name and the script would clip out your area of interest and create a GeoTiff brightness temperature image. I think the script would be able to read the metadata text file so you wouldn't have to enter those TOA radiance and K coefficients by hand. You could run the script outside of QGIS and I can probably get it to work inside of QGIS if that's easier for you.” –Ned Horning

• could create legend, but would have to specify what brightness temperature is or that the difference between the plume and the bay is in relative measurements • you could also draw a transect (draw a line, graph above it with relative temp. above the plume)