PKOJECTIONS AND GRIDS 103 



Example No. 2 



To compute the geographic position of a point whose local grid coordinates are 30,000 ft. 

 N. and 155,000 ft. W. 



(1 foot = 0.3048006096 meter) 



Origin of coordinates: Maryland 



Lat. 38°20' 426 m. Coordinate value of origin! N. or S. 0.0 feet 

 Long. 75°10' 315 m. referred to the Zero J E. or W. 0.0 feet 



Name of station: Y 



Coordinates: N. or S. 30,000 feet= 9,144 m. 

 E. or W. 155,000 feet=47,244 m. 



Latitude N.-S. coordinates 

 N. or S. 30,000 feet =9,144 m. 

 + or — seconds in meters = 426 m. 



N. or S. of 38°20' = 9,570 m. 



*From table + or — 5' = 9,250 m. 



Lat. (uncorrected) 38°25' 320 m. 

 **Curvature— = 138 m. 



***Latitude 38°25'= 182 m. 



*From special publication No. 5, page 87. 



**Correction from formula for curvature corrections, 

 page 104. 



***Use in taking out longitude values from Polyconic 

 Projection Tables, Special Publication No. 5, Coast 

 and Geodetic Survey, page 86. 



Longitude E.-W. coordinates 

 E. or W. 155,000 feet =47,244 m. 



+ or — seconds in meters = 315 m. 



E.or W. of 75°10' =47,559 m. 



***From table + or — 32' = 46,579 m. 



Longitude 75°42' 980 m. 



