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Wikipedia:Graphics Lab/Resources/QGIS/Create a topographic background

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You already have a GIS file loaded in QGIS, we will now apply to it some nice colors, then output a PNG background for our area of interest and final map.

Step 4: Add some custom colors

Main page : Wikipedia:Graphic Lab/Resources/QGis mapcolor files - for more colormap files

The topographic GIS data you downloaded is by default displayed using a monochromatic palette (mapcolors) going from white to black; however, you have the option of using other colors. You can either load an existing mapcolor file, edit an existing mapcolor file or create your own mapcolors. To do this, you will need to edit the layer's properties.

Please note that per the Wikipedia map conventions, you should use the colors provided for all topographical shading.

Loading mapcolors

For this, you will be using the Wikicarto_2.0.qml file you created earlier in this tutorial.

  1. Right click on the layer name in the Layers window and select Properties. The Layer Properties window will pop up.
  2. Under the Symbology tab, click Load Style ... at the bottom of the window.
  3. Find and select Wikicarto_2.0.qml, then hit Open.
  4. Click OK. Your map should now be in color!
  • The default layer properties window.
    The default layer properties window.
  • The final result.
    The final result.

Editing mapcolors

The Colormap tab with colors already loaded.

If you would like to edit already loaded mapcolors, simply go to the Colormap tab. There, you can add or delete entries by selecting them and clicking the appropriate buttons. You can also edit the Value, Color, and Label fields of any entry by simply double clicking on the field you wish to change. Click Apply to see the changes.

Creating mapcolors

If you would like to create your own colors from scratch—this is advised against for topographical maps, which should follow the map conventions—you can do so by following these steps on a layer which has not had colors loaded onto it:

  1. Access the Layer Properties.
  2. Under the Symbology tab, change Single band properties > Color map from Grayscale to Colormap. This will enable the options in the Colormap tab.
  3. In the Colormap tab, use the Add entry button to add colors. They will all have default values.
  4. Double click on the Value, Color, or Label fields of the entries to change them. For topography, the Value will be the altitude (ex.: 100 for 100m, 250 for 250m, and so on).
  5. Apply or OK to see the changes.

Saving mapcolors

You can save edited or created mapcolors as a style file by clicking Save Style... at the bottom of the Layer Properties window. This will allow you to apply those mapcolors to another map. If you would like to make colors—whether loaded or created—the default colors for the map, click Save As Default. This will allow you to keep editing or loading different colors while having the option to Restore Default Style if you don't like the changes you've made.

Existing color palettes

The QGis mapcolor files page already has some palettes you can use. Simply copy-paste the code into a text document, then save as PALETTENAME.qml and follow the steps above to load it into your map.

Step 5: Output your map, aka using the Print composer

This section is to redo (update/upgrade)
What we want is this: a high quality topographic output. With QGis and experience, you can get this in about 5 to 10 minutes.

You are now working with QGis, your GIS data—namely, ETOPO1—and your customized palette. To output your first topographic background, don't use File > Save as Image, which is a simple screenshot. For better quality, use the Print composer. This step will walk you through outputting a map like the one you see on the right, including a grid and an inset that lets the viewer know where in the world this section is located.

Background
  1. To give a smooth, gradient-like appearance to the colors, go to Layer > Properties > Colormap > Color interpolation (at the top), and set it to Linear.
  2. By default, the canvas of QGIS (geographic area visible in QGis) will become the area of interest for print composer.
  3. Open the Print composer: QGIS (1.7)> File > New Print Composer (Ctrl + P).

Placing the main section for output

In the print composer:

  1. On the right, under General, you can change the Size and Orientation of the image you will be outputting. A larger paper size and dpi means a higher quality, but don't go overboard! You don't want to end up with a huge file size that takes forever to upload and download.
  2. To add your map, you can either go to Layout > Add Map or click the Add new map icon in the toolbar.
  3. Click and drag in a diagonal motion across the white area to place your map. You can move it around and resize it once it's placed.

Adding a grid

  1. Make sure the placed map is selected—you will see four squares in the corners of the image when it is.
  2. On the right, go to the Item tab.
  3. Click on Grid and check the Show grid? option.
  4. Increase the Interval X and Interval Y fields. You can play around with the Offset X and Offset Y options, as well as the Grid type and Line color, until you get a grid you like. You can also turn on and change options for the border annotations.

Adding a localizer inset

 In progress

  1. step
  2. step
  3. step
Go to File > Export as Image or PDF or SVG (warning, SVG export is somewhat dodgy) and you have yourself a high quality topographic background!

Visual step-by-step

 In progress

Links

The table above has links to various tutorials and resources which can help in the creation of Wikipedia maps from digital georeferenced data (GIS).

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