What is a Maritime chart?

IA marine or maritime chart is a sailor’s version of a map and is used for navigation on water. It helps boats find their way safely into and around the harbour, and not get stuck in the mud! Maritime charts show the depth of the water, dangerous wrecks or rocks lying under the water and features such as poles, navigation marks and lights. It may leave out information that sailors do not need, such as features on land.  Mapping used to be done from ground level, as there were no aircraft to get aerial views. To look at other maps of the area, go to the Maps page.

A Modern Marine Chart

This is a bit of a modern chart showing the entrance to Chichester Harbour.  The numbers tell you how deep the water is at low tide. 4₂ indicates a depth of 4.2 meters. Look carefully and you will see that the numbers on the green bits are underlined. This tells you that the green bits are above the water at low tide and how high they are. Can you find a bit that is more than 2 meters high at low tide? The little purple teardrop shapes show the navigation marks that have lights on and the numbers and letters tell sailors how often they flash and what colour they are.

What can looking at old maritime charts show us?

We can learn about the harbour in the past, e.g: old harbour structures, such as jetties, changes in water depths and some harbour industries (although boat-building is not always shown).

We can also look for changes in the shoreline.

Murdoch Mackenzie 1786 Marine Chart (in new pop-up window)

Sheringham 1848 Marine Chart (in new pop-up window)

Can you see how the Harbour has changed?

You may need a modern map to help find your way around the old charts – look at our interactive map or click here to print off the challenges below:

Murdoch Mackenzie Chart Challenges

1. Try to work out what is water, mud and dry land on the map.
2. Find Emsworth, Bosham, Thorney Island, and practise zooming in to read the writing.
3. Start at the English Channel at the bottom (South) of the map and follow the 4 channels into the Harbour, noting the different depths.
4. How many mills can you spot in Emsworth?
5. By the numbers showing the depth of the channels are the letters m, s, or g. If m is for mud, what do you think the others stand for?  Why would sailors want to know what was at the bottom of the channel?
6.  Find the Harbour mouth. What was on the East side of it? (If you can't work it out, change the f into s) Do you know what this area is called today?

How did the Harbour change between 1786 and 1848?

Find 3 differences between the Murdoch Mackenzie and the Sheringham charts.

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Answers:
4.Two mills  5. Sand and gravel. If you know what the bottom of the channel is like it helps when trying to anchor.  Also if you hit a muddy bottom it does not damage the bottom of the boat as much as rock! 6. Customs House Watchouse. The area is called East Head today

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