Instructor Notes W5d1

Evaluation

"Grades" on BB. Should have about 15 maps by now. About 25 by next week. If I can't see them yet, let's fix that today. Remember the goal here is "I can."

One Thematic Map, All the Way Through

We will make this map:

first-fully-featured-map.png
  1. Start QGIS
  2. Open Oakland tracts layer, add water and background Alameda tracts
  3. Layer > Property > Style > Graduated > Standard Deviation > Create new color ramp (blue low, red high with pure white at 50% of the scale)
  4. Set number of classes to 6 and click "classify."
  5. Change the labels in the legend by double clicking and editing. Use
    1. Less than 1 stddev below mean
    2. From 1 std deve below up to mean
    3. From mean to one std dev above
    4. Between 1 and 2 std devs above mean
    5. Between 2 and 3 std devs above mean
    6. More than 3 std devs above mean
  6. Click on "General" tab to edit the name of the layer to "Oakland Population Density by Census Tract 2010"
  7. Create a Print Composer and add the map and the legend to it.
  8. Move the legend to the lower left and use the buttons to Align>Left and Align>Bottom
  9. Click on legend and then right click on the legend button and select the option "Item Properties"
  10. Under the "General" tab, insert a title "Map by Fname Lname" (with your name, of course).
  11. Play with the other settings to figure out what QGIS means by title, group, layer, item, symbol, and icon in this context.
    • print-composer-legend-properties02.png
  12. Under "General Options" unclick "Show Frame," set background color to a pleasant orange, and set opacity to around 50%
    • print-composer-legend-properties01.png
  13. Then click on the map to bring up its options and again go to the "General Options." Unclick "Show Frame," set background color to something neutral but contrasting with the colors in the map
  14. Click on the Grid tab. Check the "Show Grid" box and set the grid to 0.1 for both X and Y. Set the color to something like a muted gray. Contrasty enough to see, but not so heavy as to become the main visual feature of the map.
    • print-composer-map-properties-grid.png

See Hélène Draux's notes on making nice legends

Lab Assignment

  1. Repeat this above for two other modes of graduated classification.
  2. Make one of these quantiles and use 20 classes. In the print composer add a legend and notice it is way too tall. Select the legend and then right click "Item Properties" and insert a title as last time under the General tab.
  3. Go to the Legend Items tab. Select the second item and click on the minus sign below the listing box to delete it. Repeat this so that all you have left are the first item, a middle item, and the last item.
  4. Use the up and down icons to reverse the order of the legend.
  5. Use the pencil to edit each item to remove the decimal places.
    • print-composer-legend-items.png
quantile-map.png

More : see lab instructions

FAQ

  1. Why didn't we add a scalebar?
    • The spatial data for this map is based on a coordinate reference system (CRS) in degrees. For better or worse, the scalebar function uses the map's CRS to draw the scalebar in the print composer. That's great if the CRS is in feet or meters but not very helpful if it is in degrees. For more about scalebars, see Gothos' tutorial post.
  2. Can we put a legend on a pie chart (diagram) layer?
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