When it comes to visual map styles, there are always some people, who worship paper maps. In case of United States, it’s about USGS topo maps, in the UK it’s about Ordnance Survey, in case of Russia - about Soviet military topo map (slang name “Genshtab”, which means “General Command”). These people always think, that symbology of these maps is something absolutely superior, because professional cartographers were working on it for many years to make it effective. Which is true, but barely relevant to digital cartography.
Here are several reasons why this extrapolation is wrong. (For some people it’s an obvious thing, but I just like to have it here in written form to be able to refer to this diary entry in case of discussions and arguments instead of typing it every time I need it.)
Any professionally developed map style is always based on several factors: main use of specific map type, map scale (level of details), media (paper or screen).
Exactly by this reason, there are many different professionally developed standards for civilian topographic maps, hydrographic maps, military maps, aeronautical charts (and they are different, depending on altitude), marine nautical charts. In certain cases, for example - in case of nautical charts - IHO standards are universal (see IHO download page, especially - S-4 document), since it’s considered safer to have uniform styles.
Map media played huge role in case of printed maps. It was too expensive and hard to use high-resolution full-color printing before. Low resolution full-color printing is completely unacceptable for maps, since large raster dots distort small objects easily. That’s why paper maps were (and still are in some cases) printed with so called “spot colors” - inks of predefined colors (like black, brown, blue, green, orange, red, violet). And that’s why paper map styles were developed having this and only this technology in mind. At certain grade, it was true for the first digital maps too, because transflective color LCD screens were far from ideal in color reproduction and their real usable color palette was limited by less than sixteen colors. Everybody who tried to make own styles or maps for those very first Garmin or Magellan GPS devices with color LCD screens should remember that perfectly.
But modern display screen is a high contrast full-color output device, which is at least two times better in terms of contrast than common printed matter. Therefore, it is easy to use more colors and shades for map style without compromising readability. There is no risk of bad color registration (when outlines of different colors are shifted relatively to each other due to bad printing machine setup), so we can use really thin lines, if we want to. Since high quality printing became more available, technical limits of printing process are also way wider now than it was back in fifties, when majority of paper map standards (which are still in use) were initially developed. You can check out Spesifikasjon for skjermkartografi - specification for Norwegian maps, issued by national mapping agency. It’s perfect example of more or less full usage of color for different map features, which allows to put more information on map.
Purpose of any map style is the most important factor for its development. It is more obvious for people, when we comparing topographic and nautical charts, but somehow it’s not that obvious when it comes to military and hiking maps. Army has own tasks we all know about. That’s why Soviet military maps have different symbols for buildings made of wood and stone, because stone houses are fireproof. Same thing goes to roads - they are classified by several factors such as surface and width to give officers an idea, if particular road can be used by tanks and what will happen to it after they pass there. Is it enough for hiker or bicycle rider? Most likely, no. But it’s acceptable in case if there is nothing better (like in case of Russia).
To get some idea about maps style, designed for outdoor use by pedestrian, anyone should check out International Specification for Orienteering Maps and some orienteering maps available online. Orienteering maps are perfectly readable, but in the same time, they giving you huge amount of information about landmarks, terrain, vegetation and other things in very dense “package”. They even showing features like “wood, passable in one direction” (dense planted forest), “crossable and uncrossable pipelines” and many others. Is there anything like that on maps, intended for tanks? Obviously, no.
Sure, anyone is free to use whatever map one likes and to reproduce its style in MapCSS, SLD or QML, but let’s avoid doing it blindly or based on limited knowledge.