Nautical Compass

A multipurpose package of resources for reviving the Nautical Compass on maps.

I live in Greece, an insular country with long tradition in sailing. A few minutes from my home’s door there is the fishermen and the sailing boats port, at the Old Venetian Port of Heraklion, Crete. Everyday from my window I see sail boats, fishing boats, cruise ships and ferries. Nautical life is the normal for the coastal cities and villages of Greece.

Today sailors have modern GPS devices to help them navigate at the sea, but what about a few decades ago? What about centuries ago? One would be lost without a reliable compass in the middle of the ocean. And a captain should be very well trained in reading the compass and finding their way. Pick any Nautical Chart and observe the Compass Rose, a significant component of such a map.

Nautical Compasses are dynamic. They depict both True North and Magnetic North of the Earth and they need to be annualy updated, since the magnetic field of our planet is constantly changing.

When I insert a North Arrow in ArcGIS Pro I have three type options to control its orientation:

  • Map North: The north arrow points to north as defined by the rotation of the associated map frame.
  • True North: The north arrow angle points to geodetic north (to the north pole) as calculated by the coordinate system of the associated map frame, at the center of the map.
  • Magnetic North: The north arrow angle points to the north magnetic pole, as indicated by the north-seeking needle of a magnetic instrument.

A Nautical Compass in ArcGIS Pro should depict simultaneously True and Magnetic North, as well as their relative angle (the declination). And it should be capable of indicating these values at every little corner of the World.

Designing a Nautical Compass in ArcGIS Pro was not that difficult. It only needed a few concentric circles and appropriate symbology and labeling. At first place, I did this for the purposes of a map I am designing for the Cyclades island group in the middle of Aegean archipelago, but then I thought it would be a good idea to share it online with other dreamer cartographers like me.

I prepared a project package in ArcGIS Pro, which I uploaded as a downloadable item on my ArcGIS Online accountYou may freely use it under a CC BY-NC-SA 4.0 licence. So, what is in there and how one can use it?

The development part

First thing one can do is open the development part of the project, a layout with its associated map. At the table of contents there are two layer groups, one for True and one for Magnetic North.

Nautical Compass

Toggle the visibility between the two groups to see each one of them separately. You may change symbology or typography according to your taste or to your project specifications.

When happy, export each group separately in an appropriate format and then use the exported files to symbolize your own North Arrow.

For the purposes of this article and for saving valuable space, I have exported the two groups in PNG format, which is great for screen display. But if I had to produce a layout for paper printing I should export in SVG or EMF format. Even better in AIX format.

The Style file

I have saved all symbols in a style file, which is included in the project package. I have also saved the type symbology and the label placement in the same file. For the labels I have used the Josefin Sans typeface, one of my favourites.

Nautical Compass

At the style file I have also saved two symbols for North Arrow, one for the True and one for the Magnetic North.

Nautical Compass

Simply, in your own layout in ArcGIS Pro, insert two North Arrow elements, make sure they have identical size and position and style them with the available symbols in my style file.

Nautical Compass

Make sure to respectively select True North and Magnetic North at the North Arrow Type drop-down list in ArcGIS Pro.

The Production part

The production part of my project package includes the production layout and its associated map. Pay attention at the table of contents. At the COMPASS group I have inserted two distinct North Arrow elements which I have styled according to my style. Notice that the magnetic north arrow is now rotated, indicating the magnetic declination for the coordinates of the Map Frame center.

At the bottom left of the Map Frame I have added some dynamic text elements. These will change as I pan or zoom the map (whenever I activate the Map Frame) or if I select another coordinate system.

Nautical Compass

Now if you activate the Map Frame and start panning the map you may see how the magnetic north arrow freely rotates.

Nautical Compass

Another cool idea is to add to the map some contour lines of the magnetic field of Earth. I selected the from this online directory of resources provided by the NOAA Maps of Magnetic Elements from the WMM2020 webpage.

Nautical Compass

If you see that the North Arrow remains still as you pan the map, this is because of the coordinate system (epsg:3857) of the map. Try to select another coordinate system and watch the True North. It should start rotate now.

Adobe Illustrator

Not in Pro? Not a pro! I exported the development layout in an AIX file which I further loaded in Adobe Illustrator with the ArcGIS Maps for Adobe extension. I organized all layers in two separate groups, so that graphic designers can also use it.

Nautical Compass

And this is it! Here is the package on my ArcGIS Online account. Thank you for reading!

Kindest Regards from Crete, Greece



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