Use of the .lucroid in Contour Mapping 



HOURLY CORRECTIONS. 

 Read from curve for the exact hours. 



115 



Time 



Cloudy A. M. 

 Clear Day | clear?. M. Cloudy Day 



The strip method of valuation survey was used, and five 

 per cent of the area was actually covered. Strips one chain 

 wide and twenty chains apart were run across a section starting 

 at a point ten chains from the section corner. The United 

 States Geological Survey ran along the section lines when col- 

 lecting data for their contour maps, so this offset of ten chains 

 prevented covering the same ground twice. The topography for 

 ten chains on either side of the strip was mapped on a field 

 sketch. In surveyed country the strips extended in either a 

 north and south or an east and west line. As far as possible, 

 they were run in the direction of the slope up the mountain side. 

 In unsurveyed country a base-line was meandered along a valley 

 or stream bed, and the distances and elevations were obtained 

 from stadia readings. Whenever possible the base-line was tied 

 in to land surveys or to permanent land marks which had pre- 

 viously been located by the Geological Survey. From this line 

 all strips were run up the slopes. 



Each crew carried one aneroid which was read on every 

 decided change in gradient, on every ridge, peak, cliff, and on 

 the banks of lakes and streams, and at water level. The eleva- 

 tions were recorded directly on the field map at the place where 

 the topographic feature occurred. The aneroid was also read at 

 the beginning and the end of each strip-acre and the elevations 

 recorded on the sketch. In making the field sketch, a contour 

 interval of thirty-three and one-third feet was used. 



The elevations of the reconnaissance camps were determ- 

 ined either from United States Geological Survey bench marks 



