There are several questions on the site asking for standard symbology to represent markers of specific types of objects (i.e. Power Distribution, Crime Mapping, Emergency Symbols, Lakes).

What is the point of having these standard sets of markers? I think I can rationalize standard sets of symbols for elements frequently encountered in maps across many fields (such as roads or socio-political boundaries), but I don't quite get the point of cheesy point markers (such as a body outline for a homicide scene). These symbols will never be able to replace a legend, so what is the point in having them standardized?

  • What is the point of standardizing the size of a toilet paper roll? Or street signs? – Michael Todd Mar 10 '11 at 17:50
  • @Michael Todd - I think the point of standardizing a toilet paper roll and street signs are entirely different so I'm not quite sure what you are suggesting by your comment. The role of a map is sufficiently different enough than a street sign IMO to give succinct reasons for their use in maps. – Andy W Mar 10 '11 at 17:57
  • I disagree (which is, of course, my opinion). Street signs convey information just like a map; standardizing on a size, shape, color, font, font size, etc. conveys information about that sign and what it's for. Similarly, if one standardizes map layout and symbols it's immediately apparent what one is looking at when viewing the map. There is a difference in information between the two, but only in degree (again, IMO). – Michael Todd Mar 10 '11 at 18:30

It's a great question. One standard set of iconic markers with which everyone in the world is familiar is their country's set of street signs: stop, yield, crossing ahead, etc. I hope the point of such standardization is immediately obvious.

Note that the actual meanings of many of the highway symbols are not intrinsic: they must be learned (especially the international symbols used in Europe, IMHO). Unlike words (which--although they can be ambiguous--tend to be well defined and understood by literate people), icons do not have any inherent meaning. Without standardization, their use for communication relies on the ability of the reader to derive meaning on-the-fly, as it were. This is done in two ways (and both operate, to some extent, at the same time in most maps):

  • Reference to a legend.

  • Constructing meanings based on personal and cultural experiences, guessing, etc.

The first can be time consuming: it slows down map reading, makes it error-prone, and inhibits the development of a spatial "gestalt" understanding that only a good map can provide. The second will always happen to some degree and is somewhat beyond the control of the map maker. To the extent that map readers have correctly learned a standard symbology, you can circumvent both problems, thereby assuring faster, richer, more reliable communication.


Alan M. MacEachren. How Maps Work: Representation, Visualization and Design, New York : Guilford Press, 1995.

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  • and yet I have yet to meet an American driver who knows what Yield means. :-) – Ian Turton Mar 10 '11 at 19:22
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    @iant Sure we do--but it always applies to the other guy. :-) – whuber Mar 10 '11 at 19:29
  • Very much a side note, but I figured I would mention that I had Dr MacEachren as a professor for an excellent Dynamic Mapping class. Though I did not read the book mentioned in the answer above. – badkins Mar 29 '11 at 13:06

I guess the idea is that you don't have to make anything up and if your "boss" askes why something looks the way it does, you can just point him to "the standard".

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  • lol this is funny. but true. – George Silva Mar 10 '11 at 14:06
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    (+1) "it's the standard" is the most solid excuse that exists. – Pablo Mar 10 '11 at 14:33
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    +1. and developing standard compliant stuff makes sooo serious! – julien Mar 10 '11 at 14:56
  • This is true. Well ... could a "boss" answer this question? – simo Mar 10 '11 at 18:02

... such as a body outline for a homicide scene...

Summarizing: Standard Symbology is used for fast map reading.

I think that's the point of standard symbology, when you look at it you know what it means. The legend is indispensable indeed. But when you look at a standard symbol like a "body outline" the very deep of your subconscious tell you what that means so you don't have to go to the legend and compare symbols to know their meanings.

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    I agree, but I'm a bit disappointed that a standard set of symbols results in a point marker of a person taking a crap in a box to represent "illegal immigrant" (see page 27, emsymbology.org/EMS/docs/EMS_Symbology_v1.0.pdf ) – Andy W Mar 10 '11 at 14:55
  • F...!, that is the most unhappy symbol I've ever seen!!! That should be the symbol for "Chemical Bathroom". – Pablo Mar 10 '11 at 15:17
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    it's a hard concept to convey in a small symbol - at least they didn't go for a small guy in a sombrero – Ian Turton Mar 10 '11 at 16:32
  • That talk remembers me the board game "Pictionary":en.wikipedia.org/wiki/Pictionary. – Pablo Mar 10 '11 at 17:23

Thanks to vector data digital mapping methods, it is easy to produce maps with various symbologies. However, the variety of maps symbologies remains quite low, because a map based on already well established symbologies is always preferred to an 'exotic' one (except for some very specific cases). The example of national topographic maps is a good example of standardized symbologies use. In the past, some national mapping agencies have investigated on the possibility to offer different symbologies for some of their popular map series. It appeared that the users prefer the plain old traditional symbols, because they have less difficulties to read maps based on legends they sometimes know since they are kids.

GIS techniques have also changed the deal: there are many new (compared to topographic data) thematic data used and available - it makes a lot of new stuff to put on the world map. Usually, there is no tradition for the symbology of such data, and some conventions are required. Such convention are useful only for users that need to read quickly and often the same kind of maps.

Also, calling something "standard" is often a kind of marketing strategy to promote and boost its reuse by others!

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A lot of the standards work comes from the military (NATO etc) so that when you have half a dozen military forces bombing some where they can all agree what their friends and the enemy symbols are. It cuts down on so called friendly fire incidents.

A similar functionality is required when you have many local, state and federal law enforcement agencies trying to interact.

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  • I can't think of any situations in law enforcement which are analogous to the military situation. Care to elaborate or give examples? – Andy W Mar 10 '11 at 17:49
  • many teams are rushing to a bust - they get maps to their in car computers/iPhones telling them about the known offenders in the area, gun owners, paedophiles, parolees etc. It helps if they all use the same symbology so they don't shoot the undercover officer. – Ian Turton Mar 10 '11 at 18:10
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    Search & Rescue teams often request assistance from outside the city, county, state, sometimes even internationally. These groups may include local, state, and federal lw enforcement, including the military (National Guard, helicopters, etc). By having common symbols on the map, there is less confusion and they won't spend as much time figuring out how to read a map, but rather physically accomplishing the task they were asked to assist with. – RyanKDalton Mar 10 '11 at 19:11
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    @rdalton You ought to upgrade that comment to an answer: it's a good observation. – whuber Mar 10 '11 at 20:54
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    to add to rdalton's answer, agencies themselves may rarely or never be involved with out-of-district cooperative work, but what their staff? In this era of mobile citizenry many people do not work in the same town/state/province they grew up and were educated in, or had their last job. – matt wilkie Mar 10 '11 at 22:24

Because we live an happy and globalized world where any simple things is ISO-fied to make our life easier and better. GDP and happiness indices then increase and paradise story just started... Can't you feel it?

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A concepts that helps from psychology: "extrinsic cognitive load". Translated: mental work that could be avoided in understanding (in this case a map) as compared to mental work that can't.

Having a custom icon for a homicide used only on your map leads to extrinsic cognitive load because you have to check the legend, match icon in legend then remember what it is. If you have a standard icon that you recognize from other maps you probably don't have to do any legend checking at all.

Another possible advantage of a standard set of icons is that they work well as a set. Designing a set of icons is very tricky (from personal experience!), you need to:

  1. Visually differentiate all icons from each other
  2. Allow groups of icons to be visually linked (e.g. in UK OS maps all churches are variations of black crosses, chapels = just cross, church with tower = square with black cross, church with steeple = circle with black cross)
  3. Avoid visual clutter where the map just looks a mess whilst not sacrificing [1] and [2].
  4. Avoid color blindness issues and other visual problems.

Of course not all standard sets are well designed but a good one saves so much time in terms of producing an effective map that you have to have a really really good reason not to use it.

Plus as soon as most people are using a standard set you get the same network effects as social networking - the more people use it the more difficult it becomes to justify doing something different.

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  • Abit out of my ken, but an article I came recently came across an article that is directly pertinent to this topic, and so may be of interest to anyone reading this answer (Branaghan et al., 2010). – Andy W Aug 24 '11 at 20:25

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