Point sampling on raster

First phase: systematic sampling

1. Click Plugins --> Manage and Install Plugins.
2. Type in the search bar Point sampling tool, click on the plugin name and then on Install plugin.
3. Load the single band raster file C_ID.tif created by Convert vector to raster.
4. Load the regular grid as vector point file systematic_grid100.shp' created by Creating regular grid.
5. Make sure that both layers are ticked in the TOC.
6. Open the Point Sampling Tool clicking .
7. Select the layer containing sampling points.
8. Specify the output of the resulting vector file marking column with CTRL + left click.
9. Enter an output shapefile name systematic_grid100_cid.shp and path by clicking Browse.
10. Confirm with OK. The new layer is added to the Layer Panel .

Second phase: stratified random sampling with equal allocation

• In the search engine of the Processing Toolbox, type Random selection and select Random selection within subsets under Vector selection tools of QGIS.
• Select the regular point grid (result of Creating regular grid) as the input layer.
• Select the Column name containing the grouping class code as ID field.
• Enter 10 as sample size for each category.
• Click Run to execute the algorithm.
• Mark the the regular point grid in the TOC. Right click, Save as....
• Format of the output vector file is ESRI Shapefile
• Do not forget to tick Save only selected features.
• Define directory and output file name.
• Click Run to save the file.