QGIS 8 Applying prebuilt style
With data loaded, we face problems,
The data, as styled, looks horrible. It is not even displaying place names, which makes life difficult
Likely, too much data. More than likely you only want part of this data, one touwn or a shire/county
You may not have enough data. If your region of choice covers one or more tiles, you need to load all the tiles then join them
Another problem, these problems are linked. The map is generically styled, so you can’t read names—which can make cropping a region difficult. You already have too much data, adding more tiles will make this worse, much worse. And if you crop tiles, this makes new layers, which will loose any style attached.
I present the next steps in an order. But you may, as you understand what you want to do and how to do it, want to step in a different order. For example, if you know you want to splice different maps together, and can figure out what you see from the explosion on‐screen, you will probably splice first.
Styling
The basics of applying pre‐built styles. For this guide, we already have styles created by the Ordinance Survey,
Hide most of the data
On the lower left is the layer tree. Untick (hide) most layers. ‘building’ and ‘Roads’ are the layers most people would be interested in. You may also want ‘Named Places’ and ‘Administrative Boundaries’. Hidden layers make the map easier to understand
Load a style on one layer
‘Double click on a layer ‐> layer properties > Style (dialogue bottom, a button) > Load Style > from file’ (probably the only option). Navigate to the Github style download, select the QML file that styles thet layer. I often use the Backdrop style, which is for making maps onto which you will draw more information (e.g. bike routes/targetted locations). The other style produces something close to a published paper map. Then ‘Load Style > Apply > Ok’
Style all the layers you want to use
The above needs to be repeated for every layer you use. For the setup the guide uses, the ‘Roads’ layer can be difficult. There’s not one but many style options—‘casing’ and ‘fill’, for three ‘levels’ of road information. ‘fill’ styles a road as a thick line, ‘casing’ is a road outline (one line down each side). The different levels are increasing levels of road detail—‘0’ styles main roads, ‘3’ styles every road
If you can get the ‘Roads’ and ‘Buildings’ layers styled, the map will start to look usable. You will start to see a ‘real’ map appear, like the paper maps the Ordnance Survey publish. A map you can read.
Notes on styles
QGIS has a huge amount of configuration and builtin data to manage styles. There is a style manager, which is itself customisable. QGIS has similar ability to handle the elements of styles such as images and vector configurations. A heap of generic items are included. Styling in QGIS is a little world of it’s own.
This ability can have unusual effects. For example, styles can be applied by rules within a layer. Try using the Ordnance Survey ‘backdrop’ style for the administrativve boundary layer. The ‘AdministrativeBoundaries’ layer will suddenly present sub‐selection boxes in the layer dialogue, for different types of boundary.
Sometimes styling will have unwanted effects, or effects that can be unhelpful. Again talking about the ‘AdministrativeBoundaries’ layer, applying the ‘Backdrop’ style will make boundaries more or less invisible. If you think about why the creators of the style did this, it makes sense. A ‘Backdrop’ style is intended to be subdued—administrative boundaries would confuse the map. But seeing information disappear could be a shock. If not a shock, it may make you groan that now you must delve into the style and customise.
Issues can cascade through the saves and reloads. I lost all names from one map. What went wrong? I accidentally saved ‘Building’ data to the ‘Name’ layer. ‘Name’ styling has no effect on ‘Building’ data, so the layer vanished. This kind of problem is difficult to trace, because it’s not clear what has happened and there’s no information to help—QGIS is doing what I asked it to do. I found the problem after I reset the styling, to no effect. So I came to suspect the data, so checked the raw files. With the problem now known, I needed to rebuild the data for that layer. Conclusion? Map building from raw data is hard work.
End of applying style
Let’s look at map size editing
Refs
QGIS turotorial on styles,
https://docs.qgis.org/3.22/en/docs/user_manual/style_library/style_manager.html