102 NAUTICAL CHART MANUAL 



When geographic coordinates have not been computed for the area of the blueprint to 

 which they are to be apphed, it will be necessary to compute the positions on Form C&GS-89 

 "Computation of Geographic Coordinates From Plane Coordinates" described below. When 

 this is accomplished, the form is to be attached to the Chart History. 



To find the geographic position of a point whose rectangular coordinates from a known 

 geographic position are given: 



Example No. 1 



To compute the geographic position of a point whose local grid coordinates are 40,000 ft. 

 S. and 160,000 ft. E.: 



(1 foot = 0.3048006096 meter) 



Origin of coordinates: Cape Disappointment Lighthouse, Washington 



Lat. 46°16' 1038 m. Coordinate value of originJN. or S. 0.0 feet 

 Long. 124°03' 67 m. referred to the Zero JE. or W. 0.0 feet 



Name of station: X 



Coordinates: N. or S. 40,000 feet= 12,192 m. 

 E. or W. 160,000 feet=48,768 m. 



Latitude N.-S. coordinates 

 N. or S. 40,000 feet =12,192 m. 



+ or — seconds in meters= 1,038 m. 



N. orS. of 46°16'=ll,154m. 



*From table + or - 7' = 12,968 m. 



Lat. (uncorrected) 46°09' 1,814 m. 

 **Curvature— = 194 m. 



***Latitude 46°09' 1,620 m. 



*From Special Publication No. 5, page 103. 

 **Correction from formula for curvature corrections, 

 page 104. 



***Use in taking out longitude values from Poly conic 

 Projection Tables, Special Publication No. 5, Coast 

 and Geodetic Survey, page 102. 



Longitude E.-W. coordinates 

 E. or W. 160,000 feet =48,768 m. 

 + or — seconds in meters = 67 m. 



E. or W. of 124°03' = 48,701 m. 



***From table + or - 38' = 48,914 m. 



Longitude 123°25' 213 m. 



