elev1  { elevation: 10deg }
elev2  { elevation: -90deg }
elev3  { elevation: 0 }
elev4  { elevation: 100grad}
elev5  { elevation: 1.57rad}
elev6  { elevation: 0deg}
elev7  { elevation: below }
elev8  { elevation: level }
elev9  { elevation: above }
elev10 { elevation: higher }
elev11 { elevation: lower }
z { elevation: inherit }