Glacier Change Detection in GRASS GIS
Contents
Purpose
The purpose of this tutorial is to visualize and assess the change in the extent of a marine-terminating glacier in the Canadian Arctic over time. To assess the change in extent, this tutorial will demonstrate how to classify the snow/ice cover in Landsat 8/9 images using a generic Normalized Difference Snow Index (NDSI) technique. This tutorial is
Introduction
Software Download and Instillation
This tutorial is demonstrated in Windows using GRASS GIS version 8.4.0. The latest version of GRASS GIS can be downloaded here
Data Sources
This tutorial uses the green and Short-Wave Infrared (SWIR) bands from 8 Landsat 8/9 images. The images were captured in late July/august when the Fiord was mostly free of ice. The Landsat imagery can be downloaded from the USGS Earth Explorer website. To download the data, create a free student account.
The ID and metadata for the specific images used in this lab can be found in the table below.
| Landsat Image ID | Bands Used | Metadata |
|---|---|---|
| LC08_L2SP_060246_20140825_20200911_02_T1 | Example | Example |
| LC08_L2SP_046248_20150810_20200908_02_T1 | Example | Example |
| LC08_L2SP_057001_20160825_20200906_02_T1 | Example | Example |
| LC08_L2SP_046248_20180802_20200831_02_T1 | Example | Example |
| LC08_L2SP_048248_20190718_20200827_02_T1 | Example | Example |
| LC08_L2SP_074244_20200811_20200918_02_T1 | Example | Example |
| LC09_L2SP_046248_20220821_20230401_02_T1 | Example | Example |
| LC08_L2SP_067245_20230819_20230826_02_T1 | Example | Example |
| LC09_L2SP_052247_20240820_20240821_02_T1 | Example | Example |
Methods
Set Up
Import Data
Landsat imagery from USGS Earth Explorer will come in a .TAR format when downloaded. Use 7Zip file manager to extract the .TIF files.
To import the Landsat images to the workspace, go to "File" > "Import raster data" > "Import of common raster formats [r.in.gdal]"
Next, press "Browse" and find the extracted folders for the Landsat imagery. Import bands 3 and 6 for each image (.TIF files ending in "B6" and "B3"). Use a standardized naming convention for all of the images to make the analysis easier. For example, bands 3 and 6 from the 2014 image can be named L8_2014_B3 and L8_2014_B6, respectively.
