gl_space.vol

The gl_space inherits the vol property from (point)space, which uses np.prod(self.distances). As gl_space stores some condensed information in self.distances, gl_space.vol produces wrong results. The correct result can be constructed by weighting a ones-field and then summing up all the entries. Maybe there is a faster way to do this.

The default volume is somehow normalized to 12.5657994...