Sec. 22.157  Distance computation.

    The method given in this section must be used to compute the 
distance between any two locations, except that, for computation of 
distance involving stations in Canada and Mexico, methods for distance 
computation specified in the applicable international agreement, if any, 
must be used instead. The method set forth in this paragraph is 
considered to be sufficiently accurate for distances not exceeding 475 
km (295 miles).
    (a) Convert the latitudes and longitudes of each reference point 
from degree-minute-second format to degree-decimal format by dividing 
minutes by 60 and seconds by 3600, then adding the results to degrees.
[GRAPHIC] [TIFF OMITTED] TR17NO94.000


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    (b) Calculate the mean geodetic latitude between the two reference 
points by averaging the two latitudes:
[GRAPHIC] [TIFF OMITTED] TR17NO94.001

    (c) Calculate the number of kilometers per degree latitude 
difference for the mean geodetic latitude calculated in paragraph (b) of 
this section as follows:
[GRAPHIC] [TIFF OMITTED] TR17NO94.002

    (d) Calculate the number of kilometers per degree of longitude 
difference for the mean geodetic latitude calculated in paragraph (b) of 
this section as follows:
[GRAPHIC] [TIFF OMITTED] TR17NO94.003

    (e) Calculate the North-South distance in kilometers as follows:
    [GRAPHIC] [TIFF OMITTED] TR17NO94.004
    
    (f) Calculate the East-West distance in kilometers as follows:
    [GRAPHIC] [TIFF OMITTED] TR17NO94.005
    
    (g) Calculate the distance between the locations by taking the 
square root of the sum of the squares of the East-West and North-South 
distances:
[GRAPHIC] [TIFF OMITTED] TR17NO94.006

    (h) Terms used in this section are defined as follows:
    (1) LAT1dd and LON1dd are the coordinates of 
the first location in degree-decimal format.
    (2) LAT2dd and LON2dd are the coordinates of 
the second location in degree-decimal format.
    (3) ML is the mean geodetic latitude in degree-decimal format.
    (4) KPDlat is the number of kilometers per degree of 
latitude at a given mean geodetic latitude.
    (5) KPDlon is the number of kilometers per degree of 
longitude at a given mean geodetic latitude.
    (6) NS is the North-South distance in kilometers.
    (7) DIST is the distance between the two locations, in kilometers.