an instrument that measures the height above ground; used in navigation

an instrument that measures the height above ground; used in navigation

an instrument that measures the height above ground; used in navigation

brown-speckled European lark noted for singing while hovering at a great height

brown-speckled European lark noted for singing while hovering at a great height

brown-speckled European lark noted for singing while hovering at a great height

brown-speckled European lark noted for singing while hovering at a great height

brown-speckled European lark noted for singing while hovering at a great height

brown-speckled European lark noted for singing while hovering at a great height

a local region of low pressure or descending air that causes a plane to lose height suddenly