提起飞机飞行的高度来,大家也许会发生这样的问题:飞机飞得那么高,一来就高到一、二十里路,是怎么样测量出来的呢?是不是用一条长长的绳子,从飞机垂到地面上,然后再去量绳子呢?不是的,这种方法看起来似乎简单,实际上有很多技术上的困难。而且它也不能适合于各种情况的需要。现在,我们来简单地介绍一些航空上有关高度测量的知识。从什么地方量起呢?大家都晓得“海拔若干尺”这一种表示法了吧。这就是说我们把海平面算作零,然后从海平面计算高度。还有一种计算高度的方法,就是直接从当地的地面量起。这两种高度是不是相等,要看当地的地面是不是和海平面一样高。因此, When we raise the height of the plane’s flight, we may have such a problem: If the plane is so high that it is as high as one or twenty miles, how is it measured? Is it a long rope? Do you drop from the plane to the ground and then measure the rope? No, this method seems simple and actually has a lot of technical difficulties. And it cannot be adapted to the needs of various situations. Now, let’s briefly introduce some aviation knowledge about altitude measurement. From where do we measure it? Everyone knows the expression “a few feet above sea level”. This means that we count the sea level as zero and then calculate the height from the sea level. There is also a method of calculating altitude, which is measured directly from the local ground. The two heights are not equal, depending on whether the local ground is as high as sea level. therefore,