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A recent post on Cartastrophe refers to a "Worldwide Campaign to Eliminate Needless North Arrows."

So when, if ever, are North arrows necessary?

alt text

As an interesting aside the concept of North being up is not an arbitary one, but in the Northern hemisphere

"due to the visible rotation of the night sky around the visible celestial pole"

however

"Chinese and Islamic culture even considered south as the proper top end for maps."

http://en.wikipedia.org/wiki/North

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5  
Nope, I see points all over the place. (Ouch.) –  Michael Todd Nov 9 '10 at 17:41
8  
Pun was half-intended. But I didn't want to be accused of making the site go south. –  geographika Nov 9 '10 at 17:59
3  
Would YOU like to get stuck in the wilderness with an un-gridded topo map without a north arrow? –  WolfOdrade Nov 9 '10 at 20:06
    
It's funny when you put a map of Detroit, USA and Windsor, Canada where Detroit is north of Windsor. Adding the north arrow gets some interesting looks –  dassouki Nov 12 '10 at 16:10

9 Answers 9

up vote 15 down vote accepted

The most obvious use of North arrows are if UP in your map deviates from true north and this isn’t obvious to the reader.

alt text Beaulieu, de, 1646

Another use may be as a decoration, but then there is a need for something a bit juicier than the arrows provided by common GIS systems.

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1  
Precisely. I see the need in street plans that are oriented to fit a page rather than traditional north up mode. And outside of North America fewer cities are built on a N-S grid system, so it's even more important then. –  Mark Ireland Nov 9 '10 at 20:16

I think that North Arrows are similar to cargo-cult programming. "Every map up to now has had one, so we have to have one on this map too."

The only reason I can think of to include a North arrow is when the "top" of the map is not North, or when it is not immediately clear which direction is North.

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It's generally implied that North is up but I'm not ready to say they're pointless. In my daily work, I see a fair number of CAD as-built drawings. The North arrow provides much needed context.

If we're talking about the web, then I'm fine with leaving them out and I think the major web map vendors (google, bing, esri) agree.

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I was trying to think of when rotating maps would be useful - CAD plans fit this category perfectly. –  geographika Nov 9 '10 at 17:57
    
As far as webmapping goes, I have always understood the navigation arrows in the upper right to be a kind of compass rose. This is especially important in Google Earth or the various oblique image services where you can have multiple views of the same object from different angles. –  jvangeld Nov 10 '10 at 5:25
    
Indeed, until fairly recently in my field of archaeological geophysics, it was common to draw the outline of the area surveyed on a base map, then present the actual data in a separate figure aligned to the survey grid; so a north arrow was critical. This is mainly due to the limitations in software coupled with convention. Funnily enough, a piece of software commonly used for resistivity and magnetometry has just 16 orientations for each north arrow graphic, making it little more than ornamentation... –  MerseyViking Nov 4 '11 at 10:52

I remember being taught that a north arrow must be present always except in few specific cases, which actually cover 99% of maps.

You typically do not need a north arrow when:

  • there is a geographic grid present
  • the map presents a well known area to the map user, e.g. the map of the world, Europe, or your whole country on one sheet
  • the map is part of a larger map set or atlas with given standardised orientation; typically this applies to maps produced by national survey offices etc.
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I disagree with your first rule. I know FAR more people who understand the cardinal directions than can infer those directions from a lat/long grid. –  Sparr Nov 10 '10 at 0:17

No depending on the Map (90% North is up) dependent on projection

This Map: North is in all directions out from the centre (or South in all directions to the centre) - also has the graticule and text curved inline with the grat.

(uses the polar stereographic projection.)

alt text

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Nice example of North not being equal to up. –  geographika Nov 9 '10 at 19:44
1  
Out of interest what happens if you create this map in a desktop GIS such as ArcMap and create a layout with a North arrow? –  geographika Nov 9 '10 at 20:40
    
@geographika: It still points up. The only way that I know of to get a North arrow in ArcMap to not be up is to rotate the data frame the North arrow references. –  Derek Swingley Nov 9 '10 at 22:52
    
>convert to graphics and manually rotate the grouped element in the layout - for this map all points (compass points) are 'N' north - so add text boxes over the top - looks odd but works –  Mapperz Nov 9 '10 at 23:41

I've found the only time that I've needed to include a North arrow on my maps is to differentiate between grid north, true north and magnetic north. Doesn't come up often though.

Also, I totally agree with @haakon_d that they might be used as decoration, but IMO there's always a better option (including the minimalist option of not including one).

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As a curiosity: it looks as it might matter what is up what is down. At least when choosing your route.

"People making travel plans may unwittingly heed a strange rule of thumb — southern routes rule. In a new experiment, volunteers chose paths that dipped south over routes of the same distance that arched northward, perhaps because northern routes intuitively seem uphill and thus more difficult, researchers suggest."

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You'll find the north arrow in uDig actually points north, not up. Which, for map projections over a largish area is an important distinction.

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For orienteering maps, magnetic north is critical.

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