3.2. Lesson: Simbologia¶

3.2.1. Follow Along: Schimbarea Culorilor¶

Pentru a schimba simbolistica unui strat, deschideți Layer Properties. Să începem prin schimbarea culorii stratului landuse.

• Right-click on the landuse layer in the Layers list.
• Select the menu item Properties in the menu that appears.

In the Properties window:

• Select the Style tab at the extreme left:

• Click the color select button next to the Color label.

A standard color dialog will appear.

• Alegeți o culoare gri, apoi faceți clic pe OK.

• Clic iarăși pe OK din fereastra Layer Properties, apoi veți vedea schimbarea de culoare asupra stratului.

3.2.2. Try Yourself¶

Change the water layer to a light blue color.

Check your results

3.2.3. Follow Along: Schimbă Structura Simbolului¶

This is good stuff so far, but there’s more to a layer’s symbology than just its color. Next we want to eliminate the lines between the different land use areas so as to make the map less visually cluttered.

• Deschideți fereastra Proprietăților Stratului pentru stratul landuse.

Under the Style tab, you will see the same kind of dialog as before. This time, however, you’re doing more than just quickly changing the color.

• In the Symbol Layers panel, expand the Fill dropdown (if necessary) and select the Simple fill option:

• Click on the Border style dropdown. At the moment, it should be showing a short line and the words Solid Line.

• Schimbați-o pe No Pen.

• Clic pe OK

Acum, stratul landuse nu va avea nici o linie între arii.

3.2.4. Try Yourself¶

• Change the water layer’s symbology again so that it is has a darker blue outline.

• Schimbați simbolistica stratului rivers, într-o reprezentare mai sensibilă a căilor de apă

Check your results

3.2.5. Follow Along: Vizibilitate în funcţie de scară¶

Sometimes you will find that a layer is not suitable for a given scale. For example, a dataset of all the continents may have low detail, and not be very accurate at street level. When that happens, you want to be able to hide the dataset at inappropriate scales.

In our case, we may decide to hide the buildings from view at small scales. This map, for example ...

... nu este foarte utilă. Clădirile sunt greu de distins la acea scară.

Pentru a activa randarea în funcţie de scară:

• Deschideți dialogul Proprietăților Stratului pentru stratul buildings.

• Activate the General tab.
• Enable scale-based rendering by clicking on the checkbox labelled Scale dependent visibility:

• Change the Minimum value to 1:10,000.

• Clic pe OK

Test the effects of this by zooming in and out in your map, noting when the buildings layer disappears and reappears.

3.2.6. Follow Along: Adăugarea Straturilor Simbolului¶

Now that you know how to change simple symbology for layers, the next step is to create more complex symbology. QGIS allows you to do this using symbol layers.

• Go back to the landuse layer’s symbol properties panel (by clicking Simple fill in the Symbol layers panel).

In this example, the current symbol has no outline (i.e., it uses the No Pen border style).

Select the Fill in the Symbol layers panel. Then click the Add symbol layer button:

• Click on it and the dialog will change to look somewhat like this:

(It may appear somewhat different in color, for example, but you’re going to change that anyway.)

Now there’s a second symbol layer. Being a solid color, it will of course completely hide the previous kind of symbol. Plus, it has a Solid Line border style, which we don’t want. Clearly this symbol has to be changed.

With the new Simple Fill layer selected:

• Setați stilul bordurii la No Pen, ca mai înainte.

• Change the fill style to something other than Solid or No brush. For example:

• Click OK. Now you can see your results and tweak them as needed.

You can even add multiple extra symbol layers and create a kind of texture for your layer that way.

It’s fun! But it probably has too many colors to use in a real map...

3.2.7. Try Yourself¶

• Remembering to zoom in if necessary, create a simple, but not distracting texture for the buildings layer using the methods above.

Check your results

3.2.8. Follow Along: Ordonarea Nivelurilor Simbolului¶

When symbol layers are rendered, they are also rendered in a sequence, similar to the way the different map layers are rendered. This means that in some cases, having many symbol layers in one symbol can cause unexpected results.

• Give the roads layer an extra symbol layer (using the method for adding symbol layers demonstrated above).
• Give the base line a Pen width of 0.3, a white color and select Dashed Line from the Pen Style dropdown.
• Give the new, uppermost layer a thickness of 1.3 and ensure that it is a Solid Line.

Veți observa că se întâmplă acest lucru:

Well that’s not what we want at all!

To prevent this from happening, you can sort the symbol levels and thereby control the order in which the different symbol layers are rendered.

To change the order of the symbol layers, select the Line layer in the Symbol layers panel, then click Advanced ‣ Symbol levels... in the bottom right-hand corner of the window. This will open a dialog like this:

Select Enable symbol levels. You can then set the layer ordering of each symbol by entering the corresponding level number. 0 is the bottom layer.

In our case, we want to reverse the ordering, like this:

This will render the dashed, white line above the thick black line.

• Faceți clic pe Ok pentru a reveni la hartă.

Harta va arăta acum în modul următor:

Also note that the meeting points of roads are now “merged”, so that one road is not rendered above another.

When you’re done, remember to save the symbol itself so as not to lose your work if you change the symbol again in the future. You can save your current symbol style by clicking the Save Style ... button under the Style tab of the Layer Properties dialog. Generally, you should save as QGIS Layer Style File.

Save your style under exercise_data/styles. You can load a previously saved style at any time by clicking the Load Style ... button. Before you change a style, keep in mind that any unsaved style you are replacing will be lost.

3.2.9. Try Yourself¶

• Schimbați iarăși aspectul stratului roads.

The roads must be narrow and mid-gray, with a thin, pale yellow outline. Remember that you may need to change the layer rendering order via the Advanced ‣ Symbol levels... dialog.

Check your results

3.2.10. Try Yourself¶

Symbol levels also work for classified layers (i.e., layers having multiple symbols). Since we haven’t covered classification yet, you will work with some rudimentary pre-classified data.

• Creați o nouă hartă și adăugați doar setul de date roads.

• Apply the style advanced_levels_demo.qml provided in exercise_data/styles.

• Focalizați în aria Swellendam.

• Using symbol layers, ensure that the outlines of layers flow into one another as per the image below:

Check your results

3.2.11. Follow Along: Tipurile de straturi ale simbolului¶

In addition to setting fill colors and using predefined patterns, you can use different symbol layer types entirely. The only type we’ve been using up to now was the Simple Fill type. The more advanced symbol layer types allow you to customize your symbols even further.

Each type of vector (point, line and polygon) has its own set of symbol layer types. First we will look at the types available for points.

3.2.11.1. Tipurile de Straturi pentru Simbolurile de tip Punct¶

• Open your basic_map project.

• Modificați proprietățile simbolului pentru stratul places:

• You can access the various symbol layer types by selecting the Simple marker layer in the Symbol layers panel, then click the Symbol layer type dropdown:

• Investigate the various options available to you, and choose a symbol with styling you think is appropriate.
• If in doubt, use a round Simple marker with a white border and pale green fill, with a size of 3,00 and an Outline width of 0.5.

3.2.11.2. Tipurile de Straturi pentru Simbolurile de tip Linie¶

Pentru a vedea diferitele opțiuni disponibile pentru datele de tip linie:

• Change the symbol layer type for the roads layer’s topmost symbol layer to Marker line:

• Select the Simple marker layer in the Symbol layers panel. Change the symbol properties to match this dialog:

• Change the interval to 1,00:

• Ensure that the symbol levels are correct (via the Advanced ‣ Symbol levels dialog we used earlier) before applying the style.

Once you have applied the style, take a look at its results on the map. As you can see, these symbols change direction along with the road but don’t always bend along with it. This is useful for some purposes, but not for others. If you prefer, you can change the symbol layer in question back to the way it was before.

3.2.11.3. Tipurile de Straturi pentru Simbolurile de tip Poligon¶

Pentru a vedea diferitele opțiuni disponibile pentru datele poligonale:

• Change the symbol layer type for the water layer, as before for the other layers.

• Investigați ce pot face diferitele opțiuni din listă.

• Alegeți una dintre ele, pe care o găsiți potrivită.

• Dacă aveți îndoieli, utilizați Umplere cu model din puncte, având următoarele opțiuni:

• Adăugați un nou strat simbol, cu ​​o Umplere simplă, normală.

• Faceți-l în același albastru deschis, cu un chenar albastru mai închis.

• Mutați-l sub stratul simbol cu modelul din puncte, cu ajutorul butonului Move down:

As a result, you have a textured symbol for the water layer, with the added benefit that you can change the size, shape and distance of the individual dots that make up the texture.

3.2.12. Try Yourself Crearea unei Umpleri pentru SVG Personalizată¶

• Start the Inkscape program.

You will see the following interface:

Ar trebui să vi se pară familiar dacă ați folosit alte programe de editare a imaginilor vectoriale, cum ar fi Corel.

În primul rând, vom schimba canevasul la o dimensiune adecvată pentru o mică textură.

• Click on the menu item File ‣ Document Properties. This will give you the Document Properties dialog.

• Schimbați Unitățile în px.

• Change the Width and Height to 100.

• Închideți dialogul, după încheiere.

• Faceți clic pe elementul de meniu View ‣ Zoom ‣ Page pentru a vedea pagina la care lucrați.

• Selectați instrumentul Circle:

• Mențineți apăsat butonul mouse-ului și trasați pe pagină o elipsă. Pentru a transforma o elipsă într-un cerc, mențineți apăsat și butonul Ctrl pe durata desenării.

• Right-click on the circle you just created and open its Fill and Stroke options. You can modify its rendering, such as:

  • Stabiliți pentru culoarea de Umplere o culoare albastru spre gri pal,

  • Assign to the border a darker color in Stroke paint tab,
  • And reduce the border thickness under Stroke style tab.

• Draw a line using the Pencil tool:
  • Click once to start the line. Hold ctrl to make it snap to increments of 15 degrees.

  • Deplasați indicatorul pe orizontală și puneți un punct cu un simplu click.

  • Click and snap to the vertex of the line and trace a vertical line, ended by a simple click.
  • Now join the two end vertices.
  • Change the color and width of the triangle symbol to match the circle’s stroke and move it around as necessary, so that you end up with a symbol like this one:

• If the symbol you get satisfies you, then save it as landuse_symbol under the directory that the course is in, under exercise_data/symbols, as SVG file.

În QGIS:

• Open the Layer Properties for the landuse layer.
• In the Style tab, change the symbol structure by selecting SVG Fill as Symbol Layer Type option, as shown below.
• Click the Browse button to select your SVG image. It’s added to the symbol tree and you can now customize its different characteristics (colors, angle, effects, units...).

You may also wish to update the svg layer’s border (see below):

Once you validate the dialog, features in landuse layer should now be covered by a set of symbols, showing a texture like the one on the following map. If textures are not visible, you may need to zoom in the map canvas or set in the layer properties a bigger Texture width.

3.2.13. In Conclusion¶

Changing the symbology for the different layers has transformed a collection of vector files into a legible map. Not only can you see what’s happening, it’s even nice to look at!

3.2.14. Further Reading¶

Examples of Beautiful Maps

3.2.15. What’s Next?¶

Changing symbols for whole layers is useful, but the information contained within each layer is not yet available to someone reading these maps. What are the streets called? Which administrative regions do certain areas belong to? What are the relative surface areas of the farms? All of this information is still hidden. The next lesson will explain how to represent this data on your map.