9. Working with maps
|The Map View screen can be accessed by clicking on the Map View tab at the top of the screen. The Map View function allows you to view the data in your table as a thematic map.|
The Map View function also allows you to interact with the map. You can zoom in and out, select and de-select areas and switch between aerial and street views of the area.
Note: To produce a map the geographic areas in your table must be in either the row or column on their own. For example, to map the distribution of male plumbers across Sydney, you must have the geographic areas that make up Sydney in the rows, and Sex and Occupation in the columns or vice versa.
The Map View tab opens the Customise Map pane by default. You can use the tools in this pane to customise the thematic map; it will update after each customisation is made.
To close the Customise Map pane, click on the Hide button .
The Map View screen allows you to:
9.1 Navigate around your thematic mapBy using the tools at the top of the map you can move around the map.
The Single button allows you to select or de-select single areas on your thematic map.
The Freehand button allows you to select or de-select an area using a freehand (drawing) line on the thematic map.
The Rectangle button allows you to select an area using a rectangle shape. Draw a rectangle over the areas you wish to include or exclude on you thematic map.
The Apply Changes button is inactive by default. It becomes active when changes are made to the thematic map. When your changes are complete you must click on the Apply Changes button for them to take effect on the map and in your table.
The Zoom Control slider allows you to zoom in and out of the thematic map.
There are two options for viewing the thematic map. In the Street Map view this looks like a road map, and in the Aerial Map view it looks like a satellite image.
When customising your thematic map, the Information Bar will update to show what changes have been applied after each action is complete. It appears above the buttons on the thematic map. A green dot is the default and means that the screen has loaded successfully.
9.2 Select a different data item to thematically mapOnly one set of data can be mapped at a time. If your geographic areas are in the rows of your table then you can choose to map from each separate column of your table. For example, if you have the table Age by Sex for States, the data being shown might only be males aged 15-25 years for each state.
To change the data layer to be mapped:
9.3 Change the data classifierThis tool allows you to change the way the data ranges used in your thematic map are constructed.
Selecting suitable ranges depends on the distribution of data values within the data being mapped. Four range options are available:
Detailed information on each of these options is found below.
The Dalenious Hodges Algorithm is used to determine the Natural Break points. Natural Break can be an appropriate choice where data are not evenly distributed. The algorithm groups data into classes that are themselves as separate as possible, but where the data values within each class are fairly close together. That is, it maximises the differences between the classes and minimises the differences within the classes. This classification can be used to discover spatial patterns within the data, but it can lead to some classes being populated by low numbers of observations.
Equal Distribution puts the same number of records into each class. For example a data set containing 100 records will be assigned so that approximately 20 records fall into each class of a five class classification. When using Equal Distribution it is important to watch out for any extreme data values (outliers) that might affect the thematic map. These outliers will be incorporated into a class without regard to the distribution of the remaining values in the class. This method can give the most evenly coloured map but should only be considered for data sets with a nearly even distribution.
Equal Range divides records into class ranges of equal spread. For example, in a field of data values ranging from 1 to 100 the records would be assigned (in the 5 class case) into the ranges 1–20, 20–40, 40–60, 60–80 and 80–100. These ranges mean 1 to less than 20, 20 to less than 40 etc., so the classes do not overlap.
With this method classes with few or no data records can be created, depending on the distribution of your data. For example, the records 1, 4, 6, 10, 10, 89, 90, 92, 95, 100 (that is, highly skewed to either end of the overall data range) will cause the middle three classes to have no records. In this case only two colours will appear on the map. Data should therefore contain nearly evenly distributed values to produce even colour representation on the map.
Use this feature to enter your own data ranges.
The Custom Range option allows the user to manually specify class ranges. As with the other classing options the ranges are specified as, for example, 1–20, 20–40 etc. but mean 1 to less than 20, 20 to less than 40 etc. so the classes do not actually overlap. Custom ranges should always be developed with reference to the distribution of the data being mapped. The Custom Range option can be particularly useful when developing a series of maps that are designed to be compared.
9.4 Create a custom rangeWhen creating a custom range ensure all values are accounted for in the ranges, otherwise some areas may be excluded from your thematic map.
To create a custom range:
9.5 Change the number of rangesThis function allows you to change the number of ranges you wish to display in your map. The options are 1 to 5. The default display is 5.
If fewer ranges than the number chosen are required by the chosen distribution method, the lower value range colours will not be used.
9.6 Change the colours on the thematic mapThe thematic map feature has seven colour palette options. These are the colours the thematic layers of your map will appear in.
To change the colours:
9.7 Change the opacity of the thematic mapThis feature allows you to make the coloured thematic layer on the map semi-opaque so that underlying map features can be seen. The default setting shows both the themed colours and some of the underlying map details. A setting of 100% will fill the area with colour, making the details underneath the coloured areas invisible.
Note: Making the thematic layer semi-transparent can make it more difficult to distinguish the colour ranges as underlying map features show through.
To change the opacity:
9.8 Download your mapYou can download an image of your map as an Adobe Acrobat (PDF) file or KMZ File. The downloaded PDF image will be high resolution and include more detail. KMZ file allows you to upload the mapped area data into your other mapping software (e.g. Google Earth).
To download a map:
Note: Maps cannot be imported into TableBuilder. To access the same map in future sessions you need to save the table used to create the map. You can then re-open the saved table, click the Map View tab to re-create a new map.
To open your map in PDF format, you will need the Adobe Reader software. If Adobe Reader is not installed on your computer, you can download the latest version for your operating system from the Adobe website http://www.adobe.com.
For information on the use of a generalised version of ABS geographic boundaries, see Chapter 1.4.