无疑，你们熟悉地理上的等值线地图，它示出等高线。

No doubt you are familiar with geographical contour maps, which show lines of constant altitude.

youdao

无疑，你们熟悉地理上的等值线地图，它示出等高线。

No doubt you are familiar with geographical contour maps, which show lines of constant altitude.

youdao