APPENDIX I 



UNIT EQUIVALENTS 



Exact relationships shown by asteriskC). See footnote (2). 

 Area 



1 square inch = 6.4516 square centimeters* 



1 square foot = 144 square inches* 



= 0.09290304 square meter* 



= 0.00002296 acre 

 1 square yard =9 square feet* 



= 0.83612736 square meter 

 1 square (statute) mile = 27,878,400 square feet* 



= 640 acres* 



= 2.5899881 1 0336 square kilometers* 

 1 square centimeter = 0.15500031 square inch 



= 0.00107639 square foot 

 1 square meter = 10.76391045 square feet 



= 1.1 9599005 square yards 

 1 square kilometer = 247.1053815 acres 



= 0.38610216 square statute mile 



= 0.29155335 square nautical mile 

 Astronomy 



1 mean solar unit =1 .00273791 sidereal units 



1 sidereal unit = 0.99726957 mean solar unit 



1 microsecond = 0.000001 second* 



1 second =1 ,000,000 microseconds* 



= 0.01666667 minute 



= 0.00027778 hour 



= 0.00001157 day 

 1 minute =60 seconds' 



= 0.01666667 hour 



= 0.00069444 day 

 1 hour = 3,600 seconds* 



= 60 minutes* 



= 0.04166667 day 

 1 mean solar day = 24'^03'^56*55536 of mean sidereal time 



= 1 rotation of earth with respect to sun (mean)* 



= 1.00273791 rotations of earth with respect to vernal 

 equinox (mean) 



= 1.0027378118868 rotations of earth with respect to 

 stars (mean) 



1 mean sidereal day = 23'^56'^04509054 of mean solar time 



1 sidereal month = 27.321661 days 



= 27d07fi43'Ti1155 

 1 synodical month = 29.530588 days 



= 29^12*^44^0258 

 1 tropical (ordinary) year = 31,556,925.975 seconds 



= 525,948.766 minutes 



= 8,765.8128 hours 



= 365<^24219879-0'^0000000614(f-1900), where f 

 = the year (date) 



= 365'305^'48ni465 



1 sidereal year = 365<^25636042+0.000000001 1 (t-1900), where f 



= the year (date) 



= 365'^06*^09'"0955 



713 



