We know that Capt Goddard, an experienced Naval Hydrographer, with ready access to all the necessary boats and the enthusiastic help of the boys who did all the fieldwork, did make such a chart in 1948. As a major scholarship winner while the ship was still at the Bangor mooring I was one of a small party invited up to meet Capt Goddard, and there I saw this chart still unfinished on an easel in his dayroom. Sandy Kinghorn was another in that party and perhaps Sandy will remember this too. We also know that Capt Goddard presented a copy of his chart to Capt Rees-Thomas who was Caernarvon Harbourmaster at the time. The chart also shows the position where the ship finished up, which we know was 'inked in' by Capt Rees-Thomas, so we know the chart was around in 1953. Yet despite all this there are those who say we have no right to call this Goddard's chart since it doesn't bear his name. Captain Pari-Huws: "Owing to the short working period between tides, the number of boats and people involved over a lengthy period meant anyone making such a chart could not have gone unnoticed, so if this isn't Goddard's chart whose is it?"

Here I have to state that this is ' my copy ' of this chart which I've had to clean up extensively due to the very poor original photocopy. Excellent cartographer though Capt Goddard undoubtedly was, he was nothing of a freehand artist, and to my mind his three views robbed quality from the work. So I've replaced these with the equivelant views from the Admiralty Pilot. However I have kept his best one (view B, under the title) which is supposed to be the same as view 3. I've also added the sailing directons from the Admiralty Pilot and the Royal Welsh Yacht Club. If all this offends the purists who must have the original, please click HERE

On first sighting, this chart is a bit daunting with its unfamiliar ' Fulls & Changes', ' Rises & Falls' etc., but there's good reason for this. Navigation in the Strait isn't helped by the fact that each of the little places along the Strait works to a different Chart Datum. We've also seen how the tides at closely spaced points along the Strait can be radically different. But the tide at the Suspension Bridge is unlikely to differ noticeably from the tide at Menai Bridge Pier ^{(see Fig. 5, page 4)}, nor is the tide at Britannia Bridge likely to be noticeably different from the tide at Pwllfanog (Pwllfanog is the little entrance which can be seen bottom left of Fig.4). But from the chart title we can see that HW at Britannia Bridge is a full 51 minutes before HW at the Suspension Bridge only 8 cables away, and when the tidal range is 22.5 feet at the Suspension Bridge it is only 19 feet at Britannia Bridge. This, together with the different Chart Datum in use in the Strait posed an obvious problem for Capt Goddard in reducing soundings on his chart against some common denominator. But despite the big differences in the tides along the Strait, it is perhaps surprising that Mean Tide Level is common throughout its length. (Or virtually so. MTL at Portdinorwic is in fact 4 inches higher than the rest of the Strait,(^{Harvey Table 1 p_56)} which can be disregarded on a chart sounded to the nearest foot.) Here then is a common reference level which can be used anywhere in the Strait. So Capt Goddard's solution was to avoid Chart Datum altogether, and instead he reduced his soundings against a stated rise and fall (thus automatically about MTL). Nor for the purpose would it matter what rise and fall he used. As it happens he chose to use 22.5 feet which is a bit unfortunate, because that is also what the chart title states to be the rise and fall at Menai Bridge thereby introducing scope for confusion. Since the chart title clearly states that soundings between the bridges are reduced for the same rise and fall as Menai Bridge, it would be all too easy to fall into the trap of adding back to soundings the height of the tide at Menai Bridge at any instant in order to figure the depth at that time at any given point between the bridges. But with a moment's reflection this cannot possibly be the case. After HW Britannia Bridge the tide will be falling there while it is still rising at the Suspension Bridge. Even though the tidal range is less at Britannia Bridge, because the tide is so much earlier there, in the hours leading up to HW Britannia Bridge the water level there will always be higher than at the Suspension Bridge. But after HW Britannia Bridge the situation becomes reversed, and in the hours which follow it's the water level at the Suspension Bridge which will always be the highest. So it simply isn't possible to have a time/height correction to soundings which is common to all soundings between the bridges.

Instead, using Capt Goddard's chart to figure the depths, you first have to add to soundings half the stated rise and fall (11.25 feet) to bring soundings to Mean Tide Level, then add/subtract the actual height of the tide above/below MTL using the Menai Bridge tide for soundings at the Suspension Bridge, the Pwllfanog tide for soundings at Britannia Bridge, and some form of sliding scale to interpret the difference between these two extremes for soundings at any intermediate point in between. This very unusual proceedure is certainly not made obvious by the chart title. (see 'Interesting aside')