METHODS OF MAP MAKING 133 



open slopes an alternative method is to take longer shots to 

 noted objects, chain up, and compute the elevation. 



Above is practice developed in the United States For- 

 est Service. The cost is given as 12 cents per acre as a 

 total for topography and cruise. Some commercial work 

 is done on the same general plan, a five-chain tape being 

 used and correction for distance made from tables in the 

 field. 



The accompanying map of mountainous land in Idaho 

 shows at the left the topography along two miles of section 

 line as developed by a survey for control purposes which 

 surrounded four sections. This control work naturally is 

 performed and checked in advance of the detail work. 

 To the right the topography of the greater part of the area 

 has been filled in, but a strip left blank indicates how it is 

 built up, from parallel lines 10 chains apart crossing the 

 territory. This map is completed in the field, a board and 

 outline section sheets facilitating the purpose. 



This method, though developed in special conditions in 

 the West, promises, with some of its modifications, to win 

 a considerable field of employment. 



SECTION VIII 

 ADVANTAGES OF A MAP SYSTEM 



Following are the advantages which a good set of maps 

 renders to a large business concern. To secure these a 

 good man will be required in the field to keep up lines, 

 map the cutting of successive years, and watch the con- 

 dition of the timber. 



1. Great saving in the aggregate can be effected through 

 the detection of small losses, such as windfalls and insect 

 depredations, also by finding bodies of unhealthy timber, 

 and as far as possible having such material cut and hauled. 



2. The location of all sorts of roads, whether railroads, 

 logging roads, or supply roads, is greatly facilitated. 

 Exploring is saved, and distances are accurately known. 



3. Operations can be planned and largely controlled 

 from a center with all sources of information at hand. 



