应用肮空照片进行森林调查,有许多优越性。尤其在照片上测定森林郁闭度,比现地实测容易得多。因此,应用航空照片测定森林蓄积量时,郁闭度是一个重要的因子。在中小比例尺航片上测定森林郁闭度,一般采用直接目测法和模拟比较法。直接目测法,在立体镜下观察,目估确定照片上林冠面积与待测林地面积的比例。立体观察可以分别林冠本身阴影与投落阴影,以剔除投落阴影混入林冠的影响。但目估需要判读经验,估测值常常受判读员习惯偏移的影响,即所谓“人差”。模拟比较法,使用预先制作的郁闭度判读模片或选测的典型样地立体象片。在判读模片上,以涂黑园点占单位面积的比例(这个比例,可以根据需要设计,如0.10、0.15、0.20……0.95。)使用时,将照片待测区域对照不同黑白比例的郁闭度模片,取相同或相近者为森林郁闭度。典型样片,是选择的典型样地的立体象片,在地面上已实测出郁闭度等因子。依此为标准,比较待测林地,这样测定郁闭度 There are many advantages to applying forest photos to the dirty photos. In particular, the determination of forest canopy density in the photos is much easier than that actually measured. Therefore, canopy density is an important factor in the determination of forest volume using aerial photographs. Determination of forest canopy density on small and medium-scale aerial photos, generally using direct visual method and analog comparison method. Direct visual method, observed under a stereoscopic microscope, visual assessment to determine the proportion of canopy area and forest area under test. Three-dimensional observations can respectively separate the shadow of the canopy and cast a shadow, in order to eliminate the impact of falling shadow into the canopy. However, the assessment needs to read experience, the estimated value is often subject to the influence of the deviation of the interpreter, the so-called “people difference ”. Analog comparison method, the use of pre-made candelabra interpretation model or selected typical sample plots. In the interpretation of the film, the proportion of the black area accounting for the unit area (this ratio can be designed according to need, such as 0.10,0.15,0.20 ... 0.95.) When used, the photo area under test contrast different black and white shade Degree model, take the same or similar forest canopy density. A typical sample, is the typical sample of the selected three-dimensional image, has been measured on the ground canopy density and other factors. According to this as a standard, compare the forest to be tested, so measured canopy density