We are going to use two layers for this part of the lab. This does not mean you are restricted to add other layers if you feel it would improve your map. We are going to use a layer from the Ministry of Transportation of BC depicting regions where students attending UNBC come from (UNBC_Student_areas), and a prepared dataset locating a centre point of these areas (UNBC_Enrollment_Binarypoints). The dataset also has attributes that are the aggregation of the number of students from these areas attending UNBC at different times. We are going to use this point layer to depict whether student enrollment has increased or decreased in these areas and by how much.
- Creat a new folder thematic_point under your geog205 folder,
- Open a new map document and add the following layers:
- Set up the layers in a fashion that shows all the points of the Northern BC towns, the portions of the BC highways and the provincial boundary that will fit at a scale of 1:5,000,000
- We will be changing the symbology of the point layers through the next sections of the lab
The northern_towns_pop_2000_2011_2016 layer’s attribute table has many fields depicting the population numbers for each town from the years 2000, 2011 and 2016. The table also shows the changes in population for the three time periods, but we are only interested in the changes from 2011 to 2016 in this lab.
You can see columns with the population numbers for each year as well as columns for the changes from one year to another (i.e 16_11 represents the changes from 2011 to 2016). What do you think the columns with the prefix “type” in the columns header (i.e “type_16_11″) represent. HINT: why are all the values in the columns positive numbers?
In order to reduce the clutter in the attribute table and to focus on the task at hand (the changes from 2011 to 2016), you are going to hide some of the extra fields. To temporarily turn off some of the attribute table fields:
- Right click the northern_towns_pop_2000_2011_2016 -> Properties -> Fields tab. All visible fields have a checkmark.
- Click the Clear All button to remove all the checkmarks, and place a checkmark for the following five field names: NAME, POP_2011, Pop_2016,16_11 and type_16_11
Re-examine the attribute table. You should now see that all the non-checkmarked fields are hidden from view. Save changes to your map document. The attribute table remains unaltered, all its data remains on the hard drive and the instructions to hide the fields from your view are stored in your map document.
Now is a good time to save your work by the way!! Maybe something like thematic_point.mxd
Examine the attribute data more closely:
- You can get a better understanding of the data by right clicking on the field titles (headers) and sorting the field data
Q: Which communities have the larger numbers for population change ? How about the relationship between the changes in respect to town population for 2016?
Scanning attribute values in a table is informative, but a spatial representation of the locations, place names and magnitude of population changes on a map is a powerful graphical method of data representation.
Range Graded & Graduated Symbols
The remainder of this lab will be spent in designing a map that incorporates ‘graduated’ symbols. When working with graduated symbols consider the following:
- Symbol size measured in area should reflect the values being represented.
- All symbols should be visible. The smallest symbols must be bigger than dots.
- There should be some overlap to give the impression of concentrations in some parts of the map.
- Where there is overlap, the smaller symbols should retain their outline to give the visual impression of being on top
- The circle is the standard graduated symbol, but in some cases, other shapes may work better.
For ArcMap Graduated Symbols (Range Graded):
- If it is necessary to class or group the values (ArcMap graduated symbols), values should be grouped for maximum similarity within the classes and maximum variation between the classes. Class boundaries, should where possible, be round numbers (10, 50, 100 etc).
ArcMap: knowing the difference between literature terminology and software terminology
- Graduated symbols are known as Proportional symbols in the ArcMap software
- Range graded symbols are known as Graduated symbols in the ArcMap software.
- Memory tip: range graded = graduated
- For the remainder of the lab, ArcMap terms will be used
ArcMap Graduated Symbols
- Set the Data Frame Properties -> General tab Reference Scale to 1:5,000,000
- In northern_towns_pop_2000_2011_2016s -> Properties-> Symbology tab, and click on Quantities.
- Click Graduated Symbols (remember that this selection represents the range -graded symbols from lecture)
- Click the dropdown list for Value Field and choose 16_11.
- You will find these symbols are too small, and may be a poor color.
- To change, change Symbol Size range, set the upper range to 40 and the lower to 8. Click OK.
This shows the changes in Population.
Try the same methods to see how these points look when you are investigating populations values (i.e use POP_2016 for the Value field).
- Change the value field back to 16_11 before going to the next section.
Arcmap ‘graduated’ symbols (described as range graded in lecture)
Let’s evaluate what the software has done. To do this, focus on two of the points representing area, lets use Prince George and Fort Nelson.
To focus in on these two locations in the map, go to northern_towns_pop_2000_2011_2016 -> Properties -> Definition Query tab. Whatever attribute value is found to be true in the query written here will be the feature drawn on the map. All attribute values that are false are hidden from view.
Copy the following query and paste it into the query window (or try you hand at creating it on your own using the Query Builder – press the button to activate it). Make sure you copied the entire query and did not miss the ” at the beginning. You can type ” into the query yourself if needed.
“NAME” = ‘Fort Nelson’ OR “NAME” = ‘Prince George’
- Click OK.
Turn on northern_towns_pop_2000_2011_2016 labels. To remind yourself of the change in number of students from each area, you can add the 16_11 value to the label as follows:
- In northern_towns_pop_2000_2011_2016 -> Properties -> Labels tab, click the Expression button.
- Copy and paste the following expression into the expression window. Make sure you copied the initial [at the start. You can type the [into the expression yourself.
[NAME]& “-” & [type_16_11]
- Click OK
Before we investigate the results of the symbols;
Can you describe how the expression above produced the labels for the two locations?
We will be using more expressions (little scripts) further in the lab. These scripts can be handy for symbology in ArcMap, so a bit of an understanding is helpful. Using scripting for your projects is not required, so if they frustrate you – you have other options.
How do the numbers compare between the two areas? Do the size of the symbols match the numerical values? It may be easier to evaluate this if the shape were a square and not a circle.
- Return to the layer Properties -> Symbology tab and click on the Template button. Choose the green square.
Graduated symbols group the quantitative value into classes (range graded). All values within that class range are drawn on the map with the same symbol. You cannot tell the value of the individual map circle symbols, you can only match the circle to the range symbol in the legend to determine the possible range of values.
- What is the class range for Prince George?
- Does the circle/square for Prince George match the circle in the Table of Contents for that class range?
- What is the class range for Fort Nelson?
- Again, does the circle for Fort Nelson on the map match the circle in the Table of Contents for that class range?
Graduated Symbols (range graded symbols) select one symbol size for the entire range of values for each class, and as a result, you cannot determine the magnitude of individual town/city values from the map symbol, you can only match the town/city symbol on the map to a class range.
ArcMap Proportional Symbols
ArcMap ‘proportional’ symbols (described as ‘graduated’ in lectures)
- Change the symbology method to Proportional, Value field to 16_11, Unit to unknown and Min Value to 20.
Do the sizes (area) of the symbols (circle or square) appear to be proportionally represented?
Proportional symbols (graduated symbols) precisely represent the magnitude of the value.
Let’s examine the rest of the Northern towns and cities again:
- Remove the query in the Layer Properties -> Definition Query tab. OK.
- Turn the labels off
- in the Properties -> Labels tab, click the Expression button change the labeling expression back to [NAME] (Highlight the existing expression and then click the NAME value on the upper panel)
- On the Symbology tab, change the Min Value to 4 , and the number of symbols for the legend to 5. OK
With ArcGIS Proportional Symbols (graduated symbols), the area of the map symbol does represent the specific value for that map symbol, but there are a lot of sizes to visually interpret. Experiment with the Min Value, for example and try 6 or 8. Change the value back to 4.
Having experimented with both techniques, now save you map document as thematic_point_proportional.mxd.
Remember that the Reference Scale makes a huge difference on the sizing of the symbols on the map. You have it set at 1:10,000,000. If for example, you had begun the map with a 1:2,000,000 reference scale, then the sizes would be very different and you would choose different values in the symbology tab to achieve the correct cartographic look for the circles. As you design your proportional symbol map, you have the option of changing the reference scale (you don’t have to). Remember to achieve the cartographic principles discussed in lecture for this symbol technique.
STOP! What is the correct term in the literature for ArcGIS Arcmap’s proportional symbols?
- You should be able to identify a range graded symbol map when you see it (literature term).
- You should be able to identify a proportional symbol map when you see it (literature term).
- You will be questioned based on the terms from literature.
- You should be able to state the ArcGIS equivalent term.
Symbology using Multiple Attributes
Graduated (ArcGIS) range graded (literature)
Remember, we are actually working with changes in population, not actual population – so we should be looking at this differently. However, you are welcome to play around with the actual population values – or the relationship between the amount of change in relation to population. There are many ways to create thematic maps from data such as this dataset (freely available from BC Stats or Stats Canada). We are only showing some methods.
We are using the changes in population and whether population increased or decreased for each town or city. Lets look at the table in it entirety again (add all the fields back to the table for use to view). Which field do we use for indicating a positive/negative change in population – and which value represents positive/negative?
ArcMap Symbology using Multiple Attributes (no proportional symbols)
General procedure for symbology using multiple fields:
Colour the type of change
- Layer Properties -> symbology tab -> Multiple Attributes -> Quantity by Catagory.
- Value field is type_16_11
- remove the all other values (of course)
- label EACH field differently –> value 1 as Positive Change -> value 0 as Negative Change
- Change the colour of the values –> 1 coloured green and 0 coloured red
Setup symbol size
- In the same window (multiple attribute) select the symbol size window
- use the 16_11 field
- 6 classes
- symbol from 10 to 60
You now have a representation of the changes in Population and whether it is an increase or decrease in enrollment
Save your map as thematic_point_population_change_catagory.mxd
Proportional (ArcGIS) Graduated (literature)
ArcMap does not provide a method of proportional symbolization with multiple attributes, but there is a simple way to get around this. We are simply going to use the same dataset twice, but symbolize the two layers slightly different.
You should still have three layers in your map: BC boundary, Highway layer and the northern town population layer. We are going to reset the map to have proportion symbolization for the northern_towns_pop_2000_2011_2016 layer.
If your thematic_point_proportional.mxd worked out well for you, re-open it (File –> Open –> navigate to the file).
If you are not happy with the file, then re-set the symbology to proportional as we did above with a few more steps:
- Properties –> Symbology –> Quantities –> Proportional Symbols using the 16_11 field
- Leave Units as Unknown
- Min Value is set at 4 and the colour should be red
- Exclude Data; Data panel –> Exclude –> type “type_16_11″ = 1
The map now has proportional symbology for towns and cities that have a decline in population for 2011 to 2016. Lets provide the towns and cities with positive change.
Rename this layer in the Table of Contents to something like Northern Towns Decreasing
Add the northern_towns_pop_2000_2011_2016.shp file into the project again (we now have the shape file loaded twice) and rename it Northern Towns Increasing. Once the file is in we can use the symbology from the first northern_towns_pop_2000_2011_2016 layers, and adjust it somewhat.
Right click on the increasing layer:
- Properties –> Symbology –> Import –> Choose the decrease layer –> keep using the 16_11 field
- Change the colour to green (keep the min value at 4)
- Exclude Data; Data panel –> Exclude –> type “type_16_11″ = 0
Make sure the decrease layer is above the increase layer in the TOC (why?)
Adding Text Labels
When you turn on the labels for the northern_towns_pop_2000_2011_2016 layer, you can see that there are too many overlapping labels. There are a multitude ways of solving this problem. For instance you use expressions (as you did above with the definition query) to provide rules based on attribute values. You are welcome to try this – with help…
For the purpose of this lab, try to see if placement can help out
- Open the labels tab from the properties of the layer (northern_towns_pop_2000_2011_2016)
- Click on Placement Properties
- Change location – find and select “Prefer upper right, then Top Then Right
- Conflict Detection tab – set both label weight and feature weight to high
Save your work as thematic_point_enrollment_labeled.mxd
Below we will show yo tow methods for adding labels to difficult datasets such as this one.
Labeling -One Solution – tedious and not recommended (try if you want)
Add the northern_towns_pop_2000_2011_2016.shp file in as a third layer (just for practice). Place it at the top of the TOC and do the following.
First, change the position of the label relative to the feature point as follows:
- Symbology –> single symbol –> colour –> no colour
- Labels tab -> Placement Properties button –> Place label on top of point –> OK
- make sure your label field is NAME
- Close properties box
Now right click on this layer
- Label Features (turn on label features – if it is not already on)
- Convert labels to annotation
- Click on the In the map button
- click convert
You now have unattached labels (as we did by converting the legends to graphics in the last lab). You can use the pointer in ArcMap to grab the labels and move them within the map to place them where you prefer.
Labeling – Better Solution – reduce your number of features and use creative labels
If you tried the above method, remove the third version of the northern_towns_pop_2000_2011_2016 layer you used to practice with
Reduce the number of labels
You can begin to pare down the number of labels by labeling only the cities/towns that have a change in population change greater than 1000.
Create a query within the labelling expression that limits labels to those features with a population change value greater than 1000 as follows:
In northern_towns_pop_2000_2011_2016 -> Properties -> Labels tab -> Expression button, the expression is presently [NAME].
- Place a checkmark for Advanced Expression and delete everything there.
- High-light the entire expression in the Expression window – should be [NAME], and delete it (right-click selection – Delete)
- Copy and paste the following expression into the Expression window:
Function FindLabel ( [NAME], [16_11] )
if [16_11] > 1000 then
FindLabel = [NAME] & vbnewline & [16_11]
- Click OK and OK again to return to the map to view your results.
- Adjust the label text size (for example, at a reference scale of 1:5,000,000 you could try 10 points).
When you right-click a feature layer in the Table of Contents and turn Label Features on as you have done, you are creating Dynamic Labels. Dynamic Labels are being read directly from the attribute table. The default setting for the software is dropping conflicting labels. You have no control over which of the northern cities are being labelled. You can force all labels for features to draw as follows:
- Layer Properties -> Labels tab -> Placement Properties button -> Conflict Detection tab and place a checkmark at the bottom for Place overlapping labels.
Examine the results on the map. This creates a lot of overlapping labels.
You can also add a halo to your labels by:
In northern_towns_pop_2000_2011_2016 -> Properties -> Labels tab –> Symbol button –> Edit Symbol –> Mask tab. Click on Halo and set the size (thickness) to 1 or 0.5 points ( you can play around with this of course). Keep clicking OK to finish.
Example of some playing around with labels
There are many other options for labeling. For instance, if you are looking to create labeling similar to the map below, you can follow these steps:
- Return to the Labels tab and click on the Symbol button
- scroll do the list of symbols and select the Banner Text, Rounded style
- once selected, click Edit Symbol –> Advanced Text
- turn on Text Background and click its Properties
- turn on the lower balloon callout and then the Symbol button beside it
- select a colour that is slightly darker than your colour for the BC Boundary
- Click all the OK buttons until you are back at the Layers Properties Panel
- Hit Apply and OK again
- Voila labels as below
Assignment #2: Due at the beginning of next week lab session (Feb.20, 21, 22, 23)
The goal of this assignment is to produce a finished map showing the populations changes for northern towns and cities, using the proportional symbols (i.e. no range graded classes). This should be designed with:
- Letter page format 8.5 x 11 “
- Colors permitted
- Legend with a suitable sample number of symbol sizes
- Suitable background layers for context if necessary (e.g. roads, BC boundary. Background layers not required in legend if explained on the map
- Label a set of towns that have significant changes (you decide this criteria)
- Scale bar
- Suitable title and you name and date.
Note that ancillary information should be fitted around the map, such that the map has visual prominence and area, and the ancillary information is secondary.
The map area itself should fill the page as much as possible, to enable maximum details to the symbols.
- Export your map as a image file
- Make a title page with course name and number, assignment number, your name, studentID and your lab session in WORD
- Insert your map and save it as lastname_firstname_geog205_AS2.pdf
- Send your PDF file to your TA by email with subject “Geog205 AS2″