Article - Position Cross-Checking on ECDIS

Position Cross-Checking on ECDIS in View of International Regulations Requirements and OCIMF Recommendations - W. Legieć Gdynia Maritime University, Gdynia, Poland

With regards to GPS being a single source here is what this paper says:

Open Sea Navigation could be defined as part of the
ships voyage plan where no land is in vicinity [5]. At
this stage ships position is obtained with use of GPS
and could be confirmed either by Celestial Fixes or by
comparison between GPS receivers. ECDIS users will
take an advantage of having two GPS receivers what
is required by IMO on every vessel equipped with
two independent ECDIS stations

Now common sense may tell us that this is unwise, GPS being a possible “single failure point”.

But the same is true in a merchant ship with a single engine. I am familiar enough with the many procedures and so forth are in place (I have an entire engine dept aboard) and thus feel confident that failure of the engine, while always possible, is sufficiently heavily guarded against such that it is an acceptable risk.

On the other hand I don’t have a solid enough understanding of GPS to evaluate on my own if GPS is robust enough to trust as a single source in open sea navigation so I have to trust the judgment of those that do know.

the next solar flare period if one hits the earth you will find out all GPS’s are a single point failures
2022 I think will be the next one.

From the article there are two sets of standards: International regulations and OCIMF which is

The Oil Companies International Marine Forum (OCIMF) is a voluntary association of oil companies The OCIMF recommendations for tankers are higher than International regs.

The requirement for celestial comes not from the regs but from A Guide to Best Practice for
Navigational Assessments and Audits

The argument has not been made that all ships should follow OCIMF standards but that recommendation 4.01 should be followed:

Celestial navigation is regularly practiced by the bridge team members.

Vessels should be supplied with at least one sextant as a part of the navigational equipment. Sextants should be maintained in line with the maker’s instructions and safely stowed when not in use.

Navigational officers should demonstrate they are familiar with the use of the sextant and have regularly taken celestial observations (i.e. star sights), daily runs to meridian passage and sun sights, where permitted. These observations should be recorded on board in an appropriate format.

If the company requires the vessel comply with OCIMF recommendations than it would be prudent for the captain to ensure that the requirements be complied with.

On the other hand if the ship is not required to meet OCIMF recommendations and captain decides on his on that the ship should comply with the recommendations, he’d have a uphill battle on his hands.

To pick recommendation 4.01 alone and ignore the rest would be poor risk management.