The following method is suggested, using Martelli’s tables, for calculating the altitude from the dead-reckoning position. These tables are so well known for calculating the L.H.A., they need no introduction, and by using this short method for calculating the altitude, they offer one of the most complete tables in use today.
It will be seen by the following example that this method is short, simple, and accurate.
On the morning of August 12, 1932, observed sun’s lower limb, in D. R. Lat. 42°-46' N., D. R. Long. 70°-03' W., obs. Alt. 55°-06', Dec. 14°-56' N., Eq. T. —4'-54", Chro. T. 15h-llm-18s. Chro. fast 2m 43s, H.E. Cor. 11'.6.
When the latitude and declination are opposite named, the latitude and declination are added and the sum is taken to Table II, the other functions remain the same as shown.
Left stack 211
Long Beach breakwater 235
These angles are quickly drawn on a small section cut form an old chart as shown in Fig. 1.
This improvised protractor is now placed on harbor chart and properly oriented and the ship’s position quickly found. It will be noted that what has actually been done in the above procedure is to transfer the dumb rose of pelorus (with the relative bearings of chosen objects) direct to the harbor chart.
The method described will be found to be extremely accurate and without the necessity of any instruments. It offers the quickest and easiest method of determining the ship’s position while at anchor. It should be noted that relative bearings observed should be taken within shortest period of time possible to obviate errors due to swinging of vessel.