到达目标后，在圈定好的500米区域内，他们用卷尺，测径规和手持激光设备对所有树木的高度和树围进行测量。
Once there, they use tape measures, callipers and a hand-held laser to measure the heights and girths of all the trees within a 500-square-metre plot.
起初，吉林用激光束测量光在这些空气样本中的传播速度。
Originally, Keeling measured the speed of light in the air samples with a laser beam.
信使号探测器已经开始用激光高度计来测量极地火山口德地形而且已经的除了一些让人振奋的结果。
Messenger has begun testing this theory by deploying a laser altimeter to map the shape of craters at the poles - with some encouraging results.
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