4111 



HYDROGRAPHIC MANUAL 



Page 314 



Sounding Boom 



Figure 68.— General plan of a survey ship. 



4111. The Bridge 



The bridge is the most important part of a ship used for hydrographic surveys and, 

 since so many observations are taken from it, it is necessary that there be as clear a view 

 from it as practicable all around the horizon. The pilothouse is the control station 

 where all survey operations are conducted or from which they are supervised, and it is 

 obviously important that it be suitable and spacious. 



In all hydrographic surveys, except those controlled by R.A.R., the pilothouse or 

 bridge is where the positions are plotted on the boat sheet and the soundings and con- 

 trol are officially recorded, in addition to the usual navigation which is performed. In 

 hydrography controlled by visual fixes, all sextant angles are observed from the bridge 

 or the flying bridge. The echo-sounding instrument is usually inside the pilothouse, 

 the wire sounding machine is on the bridge just outside, and the handlead sounding 

 platform is on the wing of the bridge. In hydrography controlled by R.A.R., many of 

 the details are performed in the radio room and drafting room. 



During hydrographic surveys various personnel are in the pilothouse and on the 

 bridge, all of whom are busily occupied with operations which must be performed 

 quickly and accurately. In order that these operations may be efficiently performed with 

 a minimum of confusion, it is essential that the pilothouse and bridge be especially 

 designed for hydrographic surveying and that they be fully equipped and conveniently 

 arranged with the most modern navigation and survey equipment and instruments. 



