Mapping for Intensive Reconnaissance. 343 



It is a fact, that should require no argument, that a map made 

 in this manner can be no more accurate than the topographer's 

 mental conception of it. If he does not connect his lines on the 

 sheet and thus develop a complete and tangible representation of 

 succeeding impressions he can not retain a clear idea of the 

 country over which he passes. A given land form seen from one 

 strip may have a decidedly different appearance when seen from 

 the next strip, and the form lines representing it may be entirely 

 unconformable. In the office a case of this kind can be settled 

 only by guess work. 



Following such a method the mapper will perhaps develop 

 speed and, to some extent at least, his sketching ability, but his 

 judgment of perspective, of topographic forms, and of the inter- 

 relation of physical features will certainly remain latent. 



The stock argument in favor of this method is that "owing to 

 atmospheric changes which can not be allowed for in the field 

 the topographer is liable to connect form lines' of different eleva- 

 tions." Such an argument is in itself an admission that the work 

 is being done mechanically. It says in effect that the barometer 

 readings must stand, and that the topographer may not use his 

 judgment as to whether or not the reading is correct. It is based 

 on the assumption that a topographic map depends for its value 

 upon the exact location of certain contours, rather than on the 

 proper relationship of the contours to each other. 



If it were possible to locate contours accurately throughout 

 their entire length, and at close enough intervals, the resulting 

 map would necessarily be a correct representation of the topo- 

 graphy. But with reconnaissance work in rough country and 

 heavy timber it is only possible to approximate their locations, at 

 points from an eighth to a quarter of a mile apart, and usually 

 at vertical intervals of 100 feet. It is evident that under such cir- 

 cumstances the exact location alone of a few points will not give 

 a very reliable map. 



To produce a reasonably accurate map under the conditions 

 which ordinarily obtain, requires an understanding of physio- 

 graphic features, of the interrelation of land forms, of perspec- 

 tive, and more than this it requires topographic sense and imagina- 

 tion. 



To concentrate attention on the strip line and to locate contours 



