In addition to the point barrier symbols i also re-designed and extended quite a few of the existing symbols in the style for human built structures of all kinds.

Starting point was that i wanted to port back some of the changes in OSM-Carto that happened after i created the AC-Style. But i did not want to use these designs as is. Instead i wanted to re-evaluate the design decisions made in the process.

Waste and recycling

First part is the display of waste/recycling related features. OSM-Carto uses three different symbols here – for amenity=recycling, amenity=waste_disposal and amenity=waste_basket:

This approach has a number of issues:

• amenity=recycling is used for a large number of different recycling related facilities of very different size and scope. Showing them all with the same symbol is not a very good approach.
• Differentiating amenity=waste_disposal and amenity=waste_basket through generic waste bucket symbols of different size is not very intuitive. Map users will often not see both together and when seeing just one of them you don’t have the necessary context to interpret the size of the symbol as it is meant.
• The recycling symbol is poorly readable at normal resolution
• The lid of the waste_disposal symbol is oddly far from the bucket
• The choice of different colors for recycling and waste_disposal/waste_basket is not intuitively understandable
• The display of access restricted variants is not very consistent

Here is the new design schema i have developed now:

Concrete changes are in particular:

• uniform color for all symbols
• new design for amenity=waste_disposal and amenity=recycling + recycling_type=container. This depicts a classic movable waste container with wheels and hinged/sliding cover. Of course design of recycling containers varies but the basic wheeled waste container is probably known very widely and facilitates a clear intuitive distinction form amenity=waste_basket.
• re-designed recycling symbol for better readability at small sizes
• distinct symbols for generic amenity=recycling and amenity=recycling + recycling_type=centre
• more harmonic lid gap size on amenity=waste_disposal and amenity=waste_basket

Towers and masts

Towers and masts in OSM-Carto already use a systematic symbol design to visualize the different variants of construction and purpose. But this set of designs has substantial gaps. More advanced in that regard is the Röntgen icon set by Sergey Vartanov – which partly served as inspiration for the work presented here.

For better understanding: The difference between man_made=mast and man_made=tower is not completely agreed on in OpenStreetMap. As a rule of thumb: A structure that qualifies as a building (i.e. that has a human walk-able inside) is generally a tower. So is a structure that has integrated steps to walk up. Something that can only be climbed up tends to be a mast.

Here is the set of designs i use for man_made=mast:

In terms of construction that includes the four main variants (with guyed_tube being the least common). In terms of function i added designs for radar and siren.

For man_made=tower the set of symbols is more extensive:

For the main functional types (observation, communication, lighting, radar and siren) there are now distinct variants for all the main construction types – as far as they are sensible combinations. And i added rendering of tower:type=minaret.

As additional detail i introduced depiction of roof:shape to bell towers. This might be considered too detailed semantically – but it is a good demonstration how subtle design differences can be used to transport additional information.

Symbol abstraction levels

With the tower symbols you can also see that i moved the design of some of the symbols away from the solid color paradigm in OSM-Carto to a shaded depiction. Original motivation was that the OSM-Carto symbols are too variable in visual weight – leading to the heavier symbol appearing as more important in the map than the lighter ones (without there being a good reason for that).

The other reason is that the symbol design paradigm of OSM-Carto currently puts a strong emphasis on geometric clarity and simplicity of shape – up to the point that the level of abstraction severely affects intuitive understanding. Adding shading to the symbol design, limiting the level of abstraction and allowing sub-pixel details to be used where helpful can aid substantially in resolving visual ambiguities and communicating additional information in very limited space. This of course increases the demands on symbol design work.

Shading is implemented without transparency using half-toning techniques.

Other engineered structures

Here are a number of further new symbol design either newly added or as replacement for existing symbols:

The non-solid, shaded symbol designs also give room to illustrate substances stored/processed by a feature through the use of color. This has to be done carefully because color is already used for differentiating different broader categories of symbol so adding more use of color in point symbols can severely reduce map readability.

Cranes are shown in different designs depending on crane:type:

And lighthouses are, by default, rendered without the light visualization – that is only shown with the appropriate seamark tags. And for non-continuous lights a subtle variation is used.

Petroleum wells

I also added display of petroleum wells (man_made=petroleum_well) in a design derived from that of water wells. Wells tagged with pump=yes are shown with a traditional oil pump symbol. Disused wells get a symbol variation and substance (oil or gas) is differentiated by use of color.

Planters

In terms of less technical features i added rendering of man_made=planter for both nodes and polygons:

The design for polygon is derived from that of retaining walls and is simplified for small geometries. In addition, i show a hint of a shadow towards the bottom right to show the elevated nature of the feature.

Benches

I am going to close this list of new symbol designs with another one i had already developed some time ago – a new design for benches.

Benches are rendered in OSM-Carto at z19 with a uniform symbol. I extended this both in terms of zoom levels and in terms of differentiation based on additional attributes – and with support for amenity=lounger in addition.

At z18 the benches are all shown with a uniform symbol just like on OSM-Carto – but significantly smaller. This is recognizable – yet small enough to not overcrowd the map at z18 in most cases. At z19, benches with backrest get differentiated – as well as loungers. They are still shown with a smaller symbol than in OSM-Carto. At z20 and above i then show the full size symbol with

• three different symbols based on backrest=yes/no/unknown – the unknown design being inspired by Röntgen again.
• heavier and less heavy symbols based on the material – stone, concrete and metal get the heavy design, wood and plastic the lighter one. This difference is very subtle to not limit the recognizability of the symbols to be the same type of feature in principle.

Real world examples

That were a lot of different symbols so i am not going to be able to demonstrate all of them in a real world context. So just a few select examples:

Discussion

I have presented here a large number of symbol design changes and additions. Many of them are not really revolutionary but rather simple. None the less i want – in summary – point out a number of patterns in those changes and lessons to be learned here.

Designing maps for a global audience is hard because many elements that are common in some part of the world are rare or even completely unknown in others. The most obvious example from what i presented above is the minarets. But there are other things where this applies as well – siren towers/masts or petroleum wells for example. Even something like a lighthouse will be familiar to people in coastal settings while fairly unknown for those living far away from the coast. Developing a good design for those depends on real world familiarity with the various settings where these things occur. That is why a map design project with global scope heavily depends on designers with diverse geographic and cultural backgrounds and familiarity with the global geography. While OSM-Carto aims in that direction i think i have demonstrated here a bit – in the past as well as in this post – how much the choices in OSM-Carto still reflect an urban/near urban European/North American perspective. This is of course not fully the fault of OSM-Carto – mapping and tagging in OSM itself still has a similar bias.

OSM-Carto has struggled not only technically with handling a huge number of different point symbol classes. The approach to add – one by one – new primary feature classes, each with an independently developed design, had reached its limit quite some time ago. I had already shown a number of techniques that can be used to overcome this problem in the past (see links above). Methods demonstrated here are in particular:

• Aiming for depth instead of breath in terms of feature classes shown. Having recognizable base designs for broader categories of features and using subtle variations of symbols to differentiate further helps a lot in keeping symbology intuitively readable.
• Using smaller and simplified symbols at the lower zoom levels can help to avoid having too much noise in the map while maintaining the in depth differentiation at the higher zoom levels.
• Carefully using color for secondary differentiation (here: substance/content in storage structures) can help transporting additional information.
• Shading and sub-pixel design in symbols can improve readability and allows additional differentiation of symbols with limited space.

All the changes presented here can be found in the AC-Style now.