READ-ME-FIRST.txt  --  Lab 2 prepared extract: Landsat 8 red and near-infrared bands, Utah County
=====================================================================================================

WHAT THIS IS
  Two single-band GeoTIFF rasters clipped to Utah County, Utah, from one Landsat 8 scene:
    UtahCounty_Red_B4_SR_x10000.tif   Band 4 (red,  0.64-0.67 um) surface reflectance x 10,000
    UtahCounty_NIR_B5_SR_x10000.tif   Band 5 (NIR,  0.85-0.88 um) surface reflectance x 10,000
  Pixel type 16-bit signed integer, cell size 30 m, NoData = -32768 (outside the county).
  Coordinate system: WGS 1984 UTM Zone 12N (EPSG:32612), exactly as USGS delivers the scene.

WHERE IT CAME FROM
  Product ID:      LC08_L2SP_038032_20250712_20250725_02_T1
  Satellite/sensor Landsat 8, OLI/TIRS
  Acquired:        2025-07-12, 18:08 UTC (about 12:08 pm local), WRS-2 path 38 row 32
  Processing:      Collection 2, Level-2 Science Product (surface reflectance), Tier 1
  Cloud cover:     0.02 percent (whole scene)
  Source:          U.S. Geological Survey, distributed through the Microsoft Planetary Computer
                   mirror of the USGS Landsat Collection 2 archive. Retrieved 2026-09-05.
  License:         Landsat data are in the public domain (no restrictions). Please credit
                   "Landsat 8 image courtesy of the U.S. Geological Survey."
  The scene's original metadata file is included unchanged: LC08_L2SP_038032_20250712_20250725_02_T1_MTL.txt

WHAT WE DID TO IT
  1. Clipped bands 4 and 5 to the Utah County polygon (Utah county boundaries, UGRC), cell alignment
     unchanged (Extract by Mask, snapped to the source raster).
  2. Applied the Collection 2 Level-2 reflectance scale factor and offset from the metadata file:
        reflectance = DN x 0.0000275 - 0.2      (REFLECTANCE_MULT_BAND_n, REFLECTANCE_ADD_BAND_n)
     A raw USGS download does NOT have this applied. If you download your own scene you must do it
     yourself before computing NDVI, or your NDVI values will be biased toward zero (the offset does
     not cancel in the ratio).
  3. Floored the handful of slightly negative reflectance values (deep water and shadow) at 0.
  4. Multiplied by 10,000 and stored as 16-bit signed integers, LZW compressed. Dividing by 10,000
     gives reflectance (0 to 1). You do NOT need to do that for NDVI: the factor cancels in the ratio.

WHAT WE DID NOT DO
  No resampling, no reprojection, no cloud masking (there are no clouds to mask), no filtering.
  The bands are still integers, so the Float step in the lab is still necessary.

HOW TO CITE
  U.S. Geological Survey (2025). Landsat 8 OLI/TIRS Collection 2 Level-2 Surface Reflectance,
  scene LC08_L2SP_038032_20250712_20250725_02_T1. Extract prepared for BYU CE 414, 2026.
