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Landsat 7 & 8 or Sentinel-2 Snow Mapping Mammoth Mountain, CA, Example 

Related Page: Normalized Difference Snow Index (NDSI) Mapping

The USGS GloVis Next viewer shows LandsatLook and Sentinel-2 Full Resolution Browse imagery, both are SWIR/NIR/Red RGB images; snow has low SWIR reflectance and high NIR and red reflectance, and is therefore aqua. GloVis Next can essentially be used as a simple and easy snow map viewer, to get a quick snapshot of snow extent based on the most recent Landsat 7 & 8 or Sentinel-2 imagery. Imagery can be downloaded from the viewer and viewed over high-resolution imagery for a more detail assessment of snow extent. Simply complete Course 1D to understand how to use the viewer and imagery to map snow anywhere on an ongoing basis. The graphics below are of Mammoth Mountain, CA, and include Sentinel-2 and Landsat 8 imagery, which have different spatial resolution.

The map on right is a Sentinel-2 Full Resolution Browse of Mammoth Mountain on 4/27/17 (aqua is snow, or has the same SWIR/NIR/Red reflectance relationships as snow and is highly likely to be snow). 

Sentinel-2 Full Resolution Browse of Mammoth Mountain Snow Map

 

Sentinel-2 10-Meter Resolution Band 3 (Green; on right) for 4/27/17 (lighter shades are higher reflectance and represent snow)

Sentinel-2 10-Meter Resolution Band 3 Mammoth Mountain Snow Map

 

Sentinel-2 20-Meter Resolution Band 11 (SWIR; on right) for 4/27/17 (lighter shades are higher reflectance and represent snow). SWIR reflectance negatively correlates to green reflectance for snow, and is heavily absorbed. Lighter shades of SWIR correspond to darker shades of green reflectance above. The Normalized Difference Snow Index ([Green - SWIR] / [Green + SWIR]) takes advantage of this relationship.

Sentinel-2 20-Meter Resolution Band 11 Mammoth Mountain Snow Map

 

Sentinel-2 10-Meter Resolution Band 3 (Green; on right) for 4/27/17 (lighter shades are higher reflectance and represent snow) at a closer scale. The 10-meter resolution is fine enough to to represent a significant amount typical width runs. For Sentinel-2, if viewing at a close scale like below, rather than calculating NDSI (SWIR - Green) / (SWIR + Green), we recommend using the green band (band 3) solely so the 10-meter resolution is applied. If calculating with SWIR, which has 20-meter resolution, the calculated NDSI raster will have 20-meter resolution. You should view both layers individualy to make sure they negatively correlate, however.

Sentinel-2 10-Meter Resolution Band 3 Mammoth Mountain Snow Map

 

LandsatLook Snow Map (AQUA IS SNOW) (30 x 30 meter pixel size). See dates below slides; check back for NDSI map when imagery is clear. North is ↑. For scale, map is about 7.2 miles east-west and 4.5 miles north-south. North slopes may be in shadow depending on solar elevation.

          Images automatically transition every 4 seconds, or click arrows or dots - Dates Listed at Bottom.