Many times in the Home range analysis (radiotracking data) , we want minimum convex polygon. Although this method includes more area than is actually required for analysis. Read more in Analysis of Wildlife Radio-Tracking Data by Gary C. White, Robert A. Garrott. This is where minimum concave polygon comes to our rescue. Making minimum convex hull and concave hull is possible in QGIS.
1.Goto Geoalgorithm> Vector geometry tool> Concave Hull
The polygon is formed on the basis of cluster of point nearby. It reduces the actual captured area,rather than combining the holes in points placement.
2. Goto Geoalgorithm> Vector geometry tool> Convex Hull
For the same set of point in image no 1, Convex hull is created.
the resulting Concave (inner polygon) and Convex (the outer polygon) is shown in following image.