My father is a ship captain. He started this job back in the eighties and he told me all the details of the life on board at that time and how informatics improve his life and the accuracies of navigation these days.
Starting with pure navigation back in the eighties the position of a vessel was made by sextant measuring the vertical and horizontal angle of a star or the sun and then hours of calculation on paper to determinate the position with a radius of accuracy of tents of miles.Also it was very much in use estimate navigation. This mean to calculate the distance multiplying the speed with the time.The problem was that at the time it was very difficult to measure the speed of the vessel and even with a good LOCH (a device for measuring the speed through the water) that speed was not the real speed over the ground due to winds and currents. Finally the position of the ship was inaccurate and created loss of time to correct the route and losses of fuel.
Now, the GPS on board of the vessels show the permanent position of the ship with a precision of several meters using the information acquired form 5 to 7 geostationary satellites and computing all the data also displaying in real time the position, the speed and the course of the ships.
The principle of working of the system is to have a network of geostationary satellites which mean that they are turning around the earth with the same speed like the earth revolution speed itself. This satellites network cover the whole areas of the world and the radio emissions send at all time from each of them it is received on board and the device called GPS compute the distances from several satellites and the intersection of these distances in a tridimensional coordinates result in an accurate position of the ship. More positions in a time unit result the accurate speed over the ground of the ship. All of these are possible with performant computers and the results are obvious great for the economy of sea transport and also for the safety of life and cargo on sea.
Another device on board called NAVTEX receive radio information from coast stations about the weather, dangers for navigation, distress and other useful information.
These information are computed, selected in specifically order and importance and then displayed on a screen. Back in the past all this info were taken by the radio operator in MORSE code or were unavailable.
All the traffic around the vessel which is very important was monitored by sight with the binoculars or by radar. Now, another device on board of the vessels, the AIS make the ship to be visible on another screen with the name of the ship, the speed, destination, no. of crew members, drought and the minimum distance she will pass over your ship. All this dates were send and received by antennas and the computer analyzed and displaying the results. The system is received by all ships and, same time, to internet and all the data can be seen in real time by everyone like the head offices of shipping lines, agents and surveyors in different harbors or the families of the seaman.
When something is going wrong, a ship in your area take a wrong course or speed which can create a collision, you can call by radiotelephone directly that vessel on the name to alert of the danger. In areas with big traffic there are VTS (vessel traffic system) which watch the traffic at all time and permit or not the vessels to enter or not in the area surveyed.
The calculation of the cargo loaded on board was made by hand with hours of calculation. Now there are special software for loading. You just introduce the data ( drafts of the vessel, sounding of ballast tanks and bunker ) and the computer calculate the total cargo loaded on board and also the stability of the ship. The draft of a ship is the dimension measured from the keel of a ship to the waterline. Each centimeter the vessel enter in the water means tens, hundreds or even thousands of tons of cargo depends of the dimension of the ship. This is the reason to make all this calculations as accurate as possible, as soon as possible and to be checked and rechecked. The software in use today make this possible. The main engine and generators are surveyed by computers and some of modern vessels have all these information displayed in the officers cabins. Temperatures of the gases, of the cylinders, revolutions of axes, all the information must be analyzed in shortest time possible for a good function of the main engine and also auxiliary machines on board and in engine room like: generators, pumps, separators, compressors, boilers, cranes, winches, hatch covers, elevators.
All these machinery are computer controlled and the companies reduced the crews at a minimum permitted by the international marine laws. The last but not the least, the Communications. Old fashion was by radio but was not available at all time or distances due to a lot of factors which disturb the radio transmissions. Now most of the communications are made through satellites and the messages are digital encoded. Practically you have internet access all over the seas, oceans and harbors. Informatics make the life on sea much easier and much safer but also send home more than one third of the crews.
Human factor is very important but, in time, we will be replaced by machines.