为了测量高覆盖条件下(LAI=5)玉米冠层的方向孔隙率,利用一台基于工业用吊车平台的窄视角热红外成像仪开展测量。在此基础上建立了一个几何光学和辐射传输混合模型模拟半球空间的孔隙率分布。测量结果表明,大多数的孔隙出现在邻近的植株行之间,这导致了在热红外图像中,冠层还保持着垄行结构的特征。基于已经得到的几何参数,本研究发展的模型具有垄行作物孔隙率分布特征,模拟的孔隙率与被观测的孔隙率保持很好的一致。更进一步的改进,需通过计算机模拟以建立更加真实的作物结构描述,这也是以后的一个研究方向。

In order to estimate directional variation of gap frequency over a over covered maize canopy(LAI=5),an experiment using a narrow FOV thermal infrared camera mounted on a crane boom was conducted at night on July 26,1999.A geometric optical and radiative transfer model was proposed to simulate hemispherical gap frequency.Observations showed most gaps appeared between the adjacent hedgerows,which lead the canopy still to keep row feature in thermal infrared images.The measured gap frequency confirmed the results mentioned in many papers that very little azimuthal variation appeared except the observations parallel to the rows.Based on already obtained geometrical parameters,the developed model captured the main features of the measured gap frequency,the simulated gap frequency showed a fairly good agreement with observed gap frequency.