54 ANGULAR SURVEYING 



The distance between A and B is measured when the transit 

 is at A, the transitman keeping the head chainman in line; the 

 distance between B and C when the transit is at B, etc. 



Field Notes of an Azimuth Traverse. The preceding 

 notes are those of the azimuth traverse shown in the preceding 

 illustration. The distances, which are obtained by merely 

 subtracting the number of each instrument station from the 

 number of the succeeding instrument station, are recorded in 

 the fourth column. This is usually done in the office. 



LATITUDE AND LONGITUDE 



For the purposes of plotting and calculation, all the points 

 of a survey are often located with reference to two coordinate 

 axes perpendicular to each other, one being a north-and-south 

 line, true or magnetic, and called a reference meridian, or 

 principal meridian; the other, which is an east-and-west line, 

 is called a reference parallel of latitude, or principal parallel of 

 latitude. The distance of a point from the reference meridian 

 is called the longitude of the point. It is east longitude or 

 west longitude according as the point is east or west of the 

 reference meridian. East longitudes are considered positive 

 nnd west longitudes negative. The latitude of a point is the 

 distance of the point from the reference parallel of latitude. 

 It is a north latitude and considered positive when the point is 

 north of the reference parallel; it is a south latitude and is 

 negative when the point is south of the reference parallel. The 

 algebraic difference obtained by subtracting the latitude of 

 the beginning of a line, meaning the point from which the line 

 is run, from the latitude of the other extremity of the line, is 

 called the latitude range of the line. Likewise, the algebraic 

 difference between the longitude of the end and the longitude 

 of the beginning of the line is called the longitude range of the 

 line. In Fig. 1, TT' and G'G represent, respectively, a reference 

 meridian and a principal parallel of latitude. The latitudes 

 of the points P and Q are, respectively, HP and KQ; they are 

 positive. The latitudes of the points Pi, Qi, Pi, Qz are respect- 

 ively HiPi, KiQi, HzPz, and KzQt; they are negative. The 



