cases are performed to demonstrate advantages of the present invention of shadow based measurement for immeasurable projections and shadows in following cases the base points of the objects can not be located reliably or do not exist but the shadow ruler can locate the base point accurately in fig9 the shadow 1009 is measured by a dotted line and the projection 1010 is measured by a bold line the intersection of the two lines is the base point to be located fig9 a shows the measurement of an airplane in the air the airplane is in the air and has no physical base point on the ground the measured height is 57 1 m in fig9 b an overpass is measured the dotted line 1011 is the measured shadow length and the thick line 1012 is the measured projected height 13 8 m in fig9 c a tree is measured the dotted line 1013 is the measured shadow length and the thick line 1014 is the measured projected height 29 4 m fig9 d shows the measurement of a chimney whose base point can be located accurately and the height is 100 7 m the dotted line 1015 is the measured shadow length and the thick line 1016 is the measured projected height as shown in fig9 a to 9 d the base points of these objects can be inferred from the shadow endpoints when using information about the sun 39 s position and the igms and in.