北方军发现用这些气球绘制地图也很有价值，照相机发明后，航空测绘便诞生了。

The Army also found that the balloons were valuable for the use of charting the terrain, and with the newly invented photographic camera, aerial mapping was invented.

youdao

北方军发现用这些气球绘制地图也很有价值，照相机发明后，航空测绘便诞生了。

The Army also found that the balloons were valuable for the use of charting the terrain, and with the newly invented photographic camera, aerial mapping was invented.

youdao