Using Symbology feature in ArcMap 10.2 helps the User to better convey the map information to the audience. Symbols define the way points, polygons and polylines are displayed on the map to express information in qualitative or quantitative form .
In this presentation, we will be showing how the Symbology feature in ArcMap 10.2 used to express information about the theme- Population.
We will use a shapefile of Nigeria with attribute table containing data on the 2006 Census data such as the Total population per State, Male and Female population per State to carry out the demonstration. We will look at three ways of symbolizing the data.
– Qualitative– deals with non-quantitative criteria like the regional divisions of the country.For this, we will use the values in the Region Field to group the states into different regions.
– Quantitative- deals with actual quantities estimated in figures. For this, we will be using census_Tot field .
–Qualitative and Quantitative– here the two parameters can be combined to symbolize information on a map.
Attribute Table of the Shapefile Population Data. We will working with Fields= Census>Tot (Total Human population in the State), census_Mal (Population of Males in the State) and census_Fem.(Population of females in the State)
Right Click on Layer> Properties. A Layer Properties dialog box will open.
Click on the Symbology Tab and the default shown on the Left hand panel is Single Symbol.
We want to display the map showing different regions in the Country. Remember on the Attribute table each State is under a region with a regionId
We change the Single Symbol to Categories (red box), Our Value Field is Region (brown box). Then simply click Add All Values and the different regions are loaded in from the Value field (green boxes). Click Apply to view the result.
The map display has divided the country into different regions by grouping the states. In the red boxes, the values in the Field-Region are displayed on the Table of Contents under the layer. Symbology is based on categories with unique values.
Next, we want to work with the census_Tot field which is numerical or quantitative. We want to use the symbol feature to group states by population size.
Click on Quantities> Graduated colors(red box), Fill in value field as census_Tot and the figures will appear depending on the Classification into Classes (red box to the right). Once Classes are selected, the census_Tot data will be classified along a quantile color ramp.
The population data is now classified according to the census_Tot field (red boxes) showing the population sizes of the States from Low-medium-High using graduated colors.
In this illustration, we switch to using Graduated Symbols to visualize the population sizes of the States.(see red boxes)
Under the Quantities, the User can visualize the data as Charts. The Chart below represents the ratio of male to female in each state.
Combination of Qualitative and Quantitative – Multiple Attributes
Symbology features allows the User to combine qualitative symbols with quantitative symbols using the Multiple attributes option. In the demonstration below, there is a combination of attributes from the regions field (States according to regional division) and the census_Mal (Population of males per State) . Polygons grouping the States into their respective regions and the point symbol represent the relative sizes of the male population in the States. The red boxes indicate the important classification and Symbology system applied.
Start practicing folks and let us have your feedback and comments.