PROBLEM TO BE SOLVED: To provide a plant height measuring system capable of easily and stably measuring plant height from the ground of a wet plant whose roots are below the underwater ground and at least the top is on the surface of the water.SOLUTION: The plant height measuring system measures plant height from the ground of plants including wet plants the roots are in the groundwater bottom 12 and at least the upper parts of which are on the water surface 11. The plant height measuring system includes: a base 1 having a bottom face which is placed on the ground； a support post 2 extending upward from the base 1； and a non-contact distance meter 3 using reflection of a wave emitted in the air, which is supported by the support post 2 in a vertical direction. The plant height measuring device includes a predetermined high reflection part 4 supported by the base 1 in the air below the non-contact distance meter 3 and which is configured to reflect the waves and the vertical distance from the bottom face of the base 1 is known.SELECTED DRAWING: Figure 5【課題】根が水面下の地面の下にあり、少なくとも上部が水面上にある湿性植物の地面からの草丈を容易かつ安定して計測する草丈計測装置を提供する。【解決手段】草丈計測装置は、地面である水底１２の中に根があり、少なくとも上部が水面１１上にある湿性植物を含む植物の地面からの草丈を計測する。草丈計測装置は、地面に載置される底面を有するベース１と、ベース１から上に向かって延出する支柱２と、支柱２に上下動自在に支持され、空気中で発射した波動の反射を用いた非接触距離計３とを備える。草丈計測装置は、非接触距離計３より下の空気中でベース１に支持され、波動を反射させるとともに、ベース１の底面からの上下距離が既知である所定高反射部４とを備える。【選択図】図５
