A METHOD FOR MAKING TOPOGRAPHIC MAPS. 

 By L. H. Douglas. 



There is a generally recognized need of maps in many phases 

 of forestry. This need makes itself felt especially in forest 

 management where it is necessary to have a concise representa- 

 tion of the area to be managed. Topography, area, distribution 

 of types and the like can be shown at a glance. A map aids 

 in making quick and accurate decisions in logging operations, 

 location of experimental plots and various other operations in 

 management. 



The topographic map, showing as it does the lay of the land, 

 is probably fundamental in forest mapping. This map need not 

 be so accurately and carefully prepared as in the case of railroad 

 or mining operations where finer details are needed. This fact is 

 recognized by all foresters and yet, probably in many instances, 

 much needed maps are not made because of the expense and 

 time entailed. 



The object of this article is to suggest a method for making 

 topographic maps which will in a measure reduce initial expense 

 and actual time in the field. Only the instrument and field 

 methods for obtaining elevations will be explained in detail since 

 the subsequent steps in making a contour map will not differ 

 from those where the level, transit, aneroid barometer or other 

 similar instruments are used. The instrument is one designed 

 by Professor Roth, head professor of forestry in the University 

 of Michigan. So far as the writer knows it has been used only 

 locally and nothing is claimed for it except that it is an inexpens- 

 ive, quickly constructed instrument for preparing a rough contour 

 map and that it gives fairly accurate results. It consists of a 

 thin rectangular board mounted at the side and near the upper 

 end of a staff which supports an ordinary staff compass for 

 taking bearings in the field. The board revolves on a horizontal 

 bolt which fastens it to the staff. Tt is so marked off that by 

 sighting along the top to a point of known distance the elevation 

 of that point can be quickly determined by means of a plumb- 

 line suspended from the top of the 1 oard and midway between 

 its ends. 



The graduating of the board is based on the geometrical 

 relationship of similar triangles. Plate I shows the plan of the 

 board. The board may be of any convenient size but the larger 

 it is the larger the divisions and consequently the more 

 accurate the readings. Five-eighths by ten and one-half by four- 



