NOTES ON THE APPLICATION OF THE RADIO-TELE- 

 GRAPHIC SERVICE TO EXPEDITIOUS METHODS 

 ( )F GEODETIC SURVEY. 



B\ ['i;i)Ru Llms i)K Bi:llk(jaki)I£ da Silva. 



( AI'.MRACT. ) 



The author suggests that, as the introduction of wireless 

 stations o\er the Province of Mozambique is likely to take place 

 in the near future, such stations will be of great use in enabling 

 the longitudes of secondary survey ]:)oints to be determined 

 rai)idl}" and with great accuracy. 



At the ])resent time, owing to the practical ditiiculties intro- 

 duced 1)\" the rough nature and heavy alTorestation of portions 

 of the territor}', the existing methods of surveying cannot keep 

 pace Avith the demands for land measurements. However, the 

 erection of a distributing wireless station c.c/. in the vicinity of 

 the r)bservatory at Lourenco Marc|ues together with the posses- 

 sion of a ]iortable distributing and receiving wireless outfit, or 

 even of a small portable receiving outfit only, would enable the 

 Survev ! )e])artment to determine the longitudes of many points 

 throughout the Province. The determination of the precise 

 longitude of an\- |)oint recjuires two things, (i) a knowledge of 

 the local time, and ( ii ) a knowledge of the corresponding simul- 

 taneous local time at a point whose longitude is already known. 

 The first requirement is obtained by observations of stars with a 

 transit theodolite and presents no special difficulties anywhere. 

 The second part has hitherto presented many diffictilties, fre- 

 quently involving the transport of many delicate chronometers. 

 The introduction of wireless telegraphy will simplify this and 

 lead to nmch greater accuracy as all that is necessary is that the 

 .surveyors at the outstations should receive, through their wire- 

 less apparatus, signals from the clock at the Lourenco Marques 

 Obser\atory and so obtain at once with an accuracy approach- 

 ing i/icxDth of a second the difference between the simultaneous 

 local times at the two places. The method has already been fre- 

 quently utilized in Europe, thus the dift'erence of longittide 

 between L'aris and Bizerta has been determined with an accuracy 

 of between i/iooth and i/200th of a second. The author of 

 the paper hopes that in the near future these methods may be 

 actually employed in the Survey of the Province of Mozambique. 



