摄影测绘与地理研究

PHOTOGRAMMETRY AS AN AID TO THE STUDY OF GEOGRAPHY A Summary

中外地理学名家莫不视地图为研究地理的基本工具,我不是地理学家,仅是像丁文江先生在中国分省新图再版的序文里所说的:「不过懂得地图,测过,绘过,读过地图的人」。一般人对於自己所学所习的东西,总觉得特别重要,我当然不能例外,所以读到各地理名家重视地图的议论,感觉到无上的兴奋,至於他们议论的准确程度,还要请教各位地理学家。

(1)Po nts actually determined by the terrestial survey are only points occupied by the instrument and rod; details away from these points are sketches of which the accuracy depends upon the closeness of such points and the experience and ingeniousness of the surveyor. Thus the inexpressive and inexact contour lines as often found on certain topographical maps can although be improved to some extent but can not be altogether eliminated.(2)Details on maps produced by photogrammetry are plotted according to loci of points which are determined as being viewed by aid of the plotting instrument. They are determined point by point and therefore equally exact.(3)Since the introduction of stereoscopic plotting instruments and their feasibility of extending aerial polygons to a great distance, the necessity of resorting to triangulation and other tedious means of control is less needed. Some of Chinese maps were made on poor basis owing to lack of control. Therefore this condition alone would be advantageous to our geographers to have a rapid means of supplying ourselves with accurately controlled maps.(4)The inaccessibility of mountainous country and difficulty of travel in unsufficiently developed land, is no more a hindrance to surveyor working in the air.(5)The rapidness of progress is of course the essential advantage of photogrammetry. But by stereoscopic examination of photographs a vivid model of the country is seen. This facilitates the geographers to have a firsthand information before contour line maps are produeed.