THE ABNEY HAND LEVEL AND THE CHAIN ON 

 INTENSIVE FOREST SURVEYS 



By C. R. Anderson 



The articles which have appeared within the last two years on 

 control in forest surveys indicate general dissatisfaction with the 

 aneroid barometer for obtaining vertical control in mapping on 

 intensive surveys. The Abney hand level, where substituted for 

 the barometer, has proved its value. The topographers of re- 

 connaissance parties and land classification crews of the United 

 States Forest Service now condemn the use of the barometer for 

 any work except the making of very rough maps. 



It is impossible to say to what extent the aneroid barometer 

 itself is to blame for some of the poor maps made. There is no 

 doubt that poor results have been attributed to its use when 

 frequently they were due to the carelessness or inefficiency of the 

 man using the instrument ; there is, however, also no doubt that 

 foresters have expected too great a degree of accuracy from 

 its use. Experience shows that in a country of long, moderately 

 steep slopes, the aneroid barometer will give fair results. Almost 

 any other condition demands the use of some other method. 



A serious objection to the aneroid barometer is that its use 

 tends to make the mapper careless of detail in the field. The 

 correcting of the map invariably means the loss of some detail. 

 This loss of detail, however Httle it may be, has the eflfect of 

 really encouraging the man to take less detail in the field. 

 Whether the man works carefully or carelessly, the tendency in 

 the use of the barometer is in the direction of encouraging him 

 to ignore that which gives the map real value for most purposes. 

 The use of the Abney hand level, on the other hand, encourages 

 the good mapper to be a better mapper, for he can get and hold 

 detail by its use. 



The Abney hand level does, however, demand greater skill on 

 the part of the mapper than does the aneroid barometer. The 

 average member of a reconnaissance party or land classification 

 crew can show uniformly fair results with an aneroid barometer 

 after a few days' practice ; it will take him considerably longer to 

 become thoroughly familiar with the Abney hand level, and skilled 

 in its use. 



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