At various conferences and visits to police stations I have seen quite a few maps, and some have been great – really well presented, laid out and prepared. Alas many are awful, so I’ve put this page together as a brief guide to those perhaps less versed in the cartographic ways. You do not have to adhere to the guidelines here, but they might improve the readability and quality of your maps. If you do not follow these suggestions, ArcGIS will not self-destruct in a fit of cartographic rage – but this is part of the overall problem. The software does not understand your data and will let you do just about anything you want – even if it is wrong.
Note: If you are a Computer Science major and confused by the concept of sarcasm, feel free to click over to the vanilla version for you earnest types.
Tip 1: Do not include a scale bar. This will make it much more interesting as your map readers have to guess the distance between objects. One of the main aims of mapping crime is to compare areas and examine the proximity of objects, so why make it easy for the uninitiated to understand you map? Without a scale bar nobody will have a clue how far things are apart and this gives you the opportunity to have impromptu quizzes or make things up as you are presenting. If you accidentally include a scale bar use a scale that goes “0 —– 6.75 ——13.25 kilometers” instead of the usual “0 —5 —10” or similar. Big complex numbers really impress audiences.
Tip 2: Do not include a North arrow. Hundreds of years of cartographic tradition have no place in the new millennium – we are in the digital age and therefore all maps automatically have North at the top: even if we have to rotate the map to get it to fit on the page. Anyway, if you have visitors from outside your suburb, city, or country, why should they want to know in which direction is North so they can orientate themselves? They probably are not interested anyway.
Tip 3: Use jargon and special codes in the title of the map. Including special codes and police service jargon in the title of your map will make it, and you, look more professional. A title such as “B-type crimes for sectors GF and YTU for shifts R4 and R5” really impresses audiences. Make sure you also use dates in a mixture of European and American format at international conferences (without telling the audience which you are using). After all, 10/10/00 is the same either way, and what can the rest of the world teach us? Better still, don’t have a title at all (or have one that warbles on for three or more complete lines), and never put your name on the map – that way there is nobody to blame.
Tip 4: Find the color palette, and use every one. Color is what maps are all about. Use as many colors as you can find. There really are no rules about inappropriate choices of color, so bright cheerful pinks are fine for displaying child murder sites. If you have interesting symbols at particular places (such as body dump locations) try to de-emphasis them by making the background color glaring and bright. This will detract from your murder sites and make the viewer only see the underlying light industrial land use – much more important. Other features such as roads and railways and national parks are probably not very relevant, but they fill up the map nicely so give them a bold, bright color. This will further detract from your important points and distract the viewer – making them think there is less crime.
Tip 5: Don’t worry too much about understanding your data. The important thing is the presentation and the display. Don’t worry about showing maps with dots all over the place, often obscuring other dots. The audience will get the general picture and do not need complicated things like graduated circles to show how many crimes have occurred at the same place. This is just pedantic mapping for airy-fairy academics. And certainly do not worry about it when showing maps of repeat victimization. Also, if you can only geocode to the level of a zip code, still show the viewers the very best detail you can, right down to the street corner. Let “spurious accuracy” be your guide.
Tip 6: Make the most of thematic mapping. Those automatic thematic map menu items are there to be used as much as possible, and negate the need to really understand what they do. After all, it always looks great so it must be right! If you have a numerical date variable, use the graduated circle. I especially like those maps that show the time of day of an offence as a graduated circle. The bigger the circle – the later in the day. Stellar cartography right there. Another one is to use the bar graph function when comparing big numbers and little numbers. You can never see the little bars unless your nose is against the screen – how that one makes us all laugh in my office.
Tip 7: Legends have had their day. In bygone years there was a time for legends, but that age has most definitely passed. In modern cartography – especially for presentations, you will be there to explain the symbols and the values associated with different colors. And if you forget, don’t worry – the audience will understand. Hey, we’ve all done it. If you have to be passé and include a legend, then for color shaded areas use impressive looking numbers such as “3.01453 to less than 6.03215”, instead of “3 to less than 6”. This will impress the audience no end as you obviously have a grasp of quantum arithmetic.
Tip 8: Caveats look weak. You are out there to impress with your map. Having a caveat, especially for the geocoding rate, looks weak and as if you have not put enough effort in. To suggest that you have not been able to map every point will make you look bad next to all the other crime mappers who must obviously be better at it than you. After all, how can you make a good impression if you have data error? Being misleading is just helpful.
Tip 9: Get as much information onto a map as possible. Maps take time to produce so it is important to squeeze in as much information as possible. This is especially true for maps with symbols. Try and use more than 5 different types of symbol on a map, and ideally make them roughly the same size and color. It would be unfair to give added weight to one, so make them as indistinguishable as possible. If you can make them illegible from the back of a room on a PowerPoint presentation then that also helps because it makes people have to concentrate and come closer.
You could also try to disguise unhappy symbols like the locations of assaults and murders with unrelated symbols such as public lavatories and libraries. This can of course work both ways, it might suggest that there have been a lot of robberies, but most of your viewers will be fooled into thinking your area is well stocked for public utilities.
Tip 10: Never let anyone photocopy your map. A map is a work of art and should never be disseminated – ever. Stick it on the wall in the office, and use it in presentations but never let it out of your sight. Someone might take it down from the wall and photocopy it – ruining the point of the thing. Worse, they might actually use it to make a good public safety decision. The best way to teach them not to use your work is to make symbols and background colors roughly the same shade. A mid-blue and a mid-red blend nicely in color, producing a pleasing effect on the eye, but are indistinguishable when photocopied into grayscale. That will teach them to steal your maps!