# Tutorial Zonal Statistics and Area Computations

Completion requirements

### 1. Introduction

For many studies it is important to know the statistics of a continuous raster for discrete units (in raster or vector format). For example, the average elevation per subcatchment, the maximum NDVI per land-cover class, etc. In this tutorial you'll explore several tools available in QGIS for calculating zonal statistics and compute surface areas.

After this lesson you will be able to:

- calculate zonal statistics from a continuous raster layer using areas defined by a polygon vector layer
- calculate zonal statistics from a continuous raster layer using zones in a discrete raster layer
- calculate the surface area of classes in a discrete raster
- calculate the surface area of classes in a discrete raster per area defined by a polygon vector layer
- calculate other univariate statistics from raster layers

In this lesson we will use the following data that is provided as a GeoPackage from the main module page:

- subcatchment layer with polygons delineated from the DEM
- DEM raster derived from the SRTM 1-Arc Second product. Downloaded from USGS Earth Explorer and further processed in QGIS.
- CORINE 2018 Land Cover 100 m raster provided by Copernicus
- NDVI derived from a Sentinel 2 image of 7 May 2020. Downloaded from USGS Earth Explorer and further processed in QGIS.