இந்த Publication Issue உங்கள் மொழியில் இல்லை, இதில் பார்க்கவும்: English (en),
அல்லது Google Translate பயன்படுத்த:  

The humid landscape is water controlled, and unless it is an extremely new landscape- volcanic or newly faulted--it has softly rounded outlines. When you are walking up the valley, or walking on the ridge, observe that there is a rounded 'S' shaped profile to the hills.

Where the landscape turns from convex to concave occurs a critical point that we call a keypoint.*


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