These days, maps can be found in every walk of life. Access to digital maps from desktop computers, smartphones, and even the gratuitous use by cable/ TV newsrooms allows individuals who previously may not have ever looked at a map to have a hands-on experience. So now that maps are consumed by even the most uninformed of us on a myriad of topics, are there ways to ensure my map simply and easily communicates what I intend?
Just as there are in other media types, there are “good” maps and there are “bad” maps. This distinction is sometimes quite stark,where other times it is very subjective. “What, then, makes a good map?” you may ask. But it's a question that cannot be answered in a mere blog post. There are entire books written on the topic. Color choices, element size and styling, level of detail, fonts, and scale are all elements factoring the relative “goodness” or “badness” of a map. With that said, however, there are several non-aesthetic elements that are essential for accurate and easily interpretable map presentations.
I can’t take credit for the following list. A college Teacher Assistant I had for a GIS class passed along the following acronym, and to his credit, has stuck with me to this day: T.O.S.S.L.A.D.
Title: Every map should have a title. It allows the user to assess the purpose of the map quickly; allowing them to determine if it meets their needs.
Origin: A fancy name for a compass or North arrow. This allows the user to determine the maps reference to the earth. While most maps these days have North being straight up, occasionally you will encounter a map that has a skewed orientation, perhaps to better fit it on the physical medium its presented on (i.e. paper), or simply because it’s easier to interact with the map in that orientation.
Scale: Ensure there is a scale bar on the map. This allows the user to determine relative measurers of distance. Is this road I am looking at 1 mile long? 10 miles long? 1 foot long? Knowing map scale is essential in map interpretation.
Source: This is a two-fold element: It allows the map maker to provide the map viewer an idea where the data the map is representing is from; a necessity in determining the accuracy of a map. It also allows the map maker a way to cite the source of their data, avoiding all those pesky cries of plagiarism and the ensuing lawsuits. You have better uses for your time, like ensuring the rest of the T.O.S.S.L.A.D. elements are on your maps.
Legend: Not the myth, but the area where a user can determine what a particular color or symbol represents on the map. Without a legend, a user cannot successfully interpret what your map is trying to represent, “Does the red skull and crossbones over my favorite restaurant mean what I think it means?
Author: Hey, take credit for your creation. It also lends credibility to a map document, especially if you are Dr. Noel Manfrrangensennn, PhD, JSK, ASEP, KOPA, and not Billy Addams, 2nd Grader, Middle Elementary School.
Date: When was this cartographic masterpiece made? If your map was created in 1962 and shows commuter levels in Chicago – it might not be such a valid source for the traffic data you are looking for today, unless you are feeling nostalgic.
There you have it. Ensure that every map you create incorporates T.O.S.S.L.A.D., and you are on your way to cartographic genius. Now we just need to work on your penchant to use hot pink and yellow for your font colors.