Most of the projected coordinate systems we use to create maps of the World use the Greenwich meridian as the prime meridian. From time to time my clients ask me whether this can be changed and how to make a map centered on the International Date Line rather than the Greenwich meridian or how to center the ArcMap’s data frame on Australia. Let’s have a look at how to achieve this in ArcGIS for Desktop.
To add some fun to this task let’s also rotate the map upside down so that Australia will be displayed on top of the World. I’m sure that most of you saw The Upside Down World Map, which is very popular among tourists and even I have one hanging on the wall at home. So how did they make this map?
The workflow in ArcGIS Desktop will include two simple steps:
1. Change the prime meridian for your map projection in ArcMap
2. Rotate the Data frame by 180 degrees.
I used a simple map of the world with political boundaries (Esri test data created in 2005) and it uses one of the common projections called Plate Carre, also called equidistant cylindrical projection or geographic projection. This map projection is mathematically simple and it is believed to be one of the oldest map projections in the world – some researches suggest that cartographers have been using it since AD 100. This map projection displays maps both meridians and parallels as straight lines of constant spacing and this projection is quite commonly used for maps of the World in GIS.
The default prime meridian is of course Greenwich, so if you zoom to the full extent Image may be NSFW.
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the map will be centered on it.
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Open the Data Frame Properties and navigate to the Coordinate System Tab.
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Find the projection that is currently being used by the data frame (or the one you’d like to project that data to), right-click and choose Copy and Modify.
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Type in the new name and change the longitude of the prime meridian to 180 (or the one you need):
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In my example IDL stands for International Date Line.
Hit OK and the new projection will appear in Custom list:
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Apply this projection and now your map will be centered on the 180E meridian:
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Let’s have some fun and let’s turn the world upside down, so that Australia will show on the top.
Open the Data Frame Properties again and navigate to the General Tab. Set the Rotation to 180 degrees.
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Hit Ok and examine the results.
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You can try setting a different prime meridian for your custom map projection, i.e. the 146E one will place Australia in the center and won’t cut Africa or South America into halves.
Then simply add some basemap layers, like major cities, rivers and labels for countries and switch to the layout view to add legend, grids and a title.
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Well, your Aussie-centered map of the World is ready to be printed or published!
Having fun with GIS is easy!
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