Notes for Portal Landsat NDVI
Generated by: Erica Christensen (03/12/2018)


USGS Landsat Product Guide: https://landsat.usgs.gov/sites/default/files/documents/si_product_guide.pdf
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Data Citation:

Landsat Spectral Indices products courtesy of the U.S. Geological Survey Earth
Resources Observation and Science Center.

For Landsat 4-5 TM or Landsat 7 ETM+:
Masek, J.G., Vermote, E.F., Saleous, N., Wolfe, R., Hall, F.G., Huemmrich, F., Gao, F.,
Kutler, J., and Lim, T.K. (2006). A Landsat surface reflectance data set for North
America, 1990-100, IEEE Geoscience and Remote Sensing Letters. 3:68-72.

For Landsat 8 OLI/TIRS:
Vermote, E., Justice, C., Claverie, M., & Franch, B. (2016). Preliminary analysis of the
performance of the Landsat 8/OLI land surface reflectance product. Remote Sensing of
Environment, 185, 46-56.

Reprints or citations of papers or oral presentations based on USGS data are welcome
at the User Services addresses included in this guide. Such cooperation will help USGS
stay informed of how the data are being used.

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Monthly timeseries of Landsat NDVI data for the Portal site is in LandsatNDVI_monthly.csv

Center Pixel: 31.937769, -109.08029 (approx center of Portal Project if site envisioned as a square)
Raster images were clipped to a square approximately 2.25km x 2.25km centered at the pixel above, to align with a previous project using MODIS NDVI data.
Bad pixels were removed from raster images, according to a 'Pixel QA' layer obtained with each original NDVI raster.

List of all Landsat Products used for this project is contained in LANDSAT_files.csv
Code used to clip and summarize these rasters is in get_landsat_data.R
Summaries of each clipped raster are contained in LandsatNDVI_raw.csv (this includes images that were 100% cloud, and therefore data is NA).

From LandsatNDVI_raw.csv, I filtered out all images with >50% cloud (or 50% unusable pixels), and averaged by month to create Landsat_monthly_NDVI.csv.


