The Digital Elevation Models (DEMs) often contain artefacts introduced mostly during different processing steps in the framework of this plugin, such as interpolation.

The tool Remove Artefacts helps to eliminate these artefacts from the DEM raster. The polygons drawn before this window emerges, are used to specify the area where artefacts will be removed. The values defined by the mathematical expression you enter will be considered artefacts.

Choose a comparison operator:
Your expression should consist of simple comparison operators such as ">", "<", "==", etc. They can be selected from this drop-down menu, or you can write them in the text box yourself. You can also use any form of "NoData" (No data, no data, nodata, NODATA, etc.) to refer to empty pixels. In this case no pixel will be erased, and the empty pixels will simply be filled with interpolated values.

Enter your expression:
Enter the expression that will define which elevation values are to be considered as artefacts and thus removed. The expression must contain the letter H (height) which refers to the value of the pixels in the DEM.

Interpolate values for removed cells:
Check this box to fill in the gaps left by removed pixels. If this option is not selected, a gap will be left for each removed pixel.

Click add more polygons to go back to the map and draw another polygon. Keep in mind the same expression will be applied to every polygon you draw.

Advanced parameters:
Check Save mask layer to save the polygons drawn here. The file path should be specified under Output file path. If no path is specified, the shapefile will be saved in your OS temporary folder.

Output file path:
If there is no path specified here, the file will be created in the temporary folder. The full path will be shown in the Log tab and the result will be loaded to the map canvas.

Warnings:
I) Please avoid using these characters in the file name, as they might cause processing errors: ( ) / - % $ @ #
II) The polygons you draw while using this tool are temporary and will be erased as soon as the processing is finished, unless you specify otherwise.
Note: If this tool is used repetitively with no path specified, previous results will be overwritten. To avoid this, specify a different path (or filename) each time