Map Viewer allows you to explore data in various ways through a variety of smart mapping styles. When you style map layers in Map Viewer, the nature of the data determines the default styling options. You can experiment with color ramps, line weights, transparency, symbols, and other graphic elements, and see your choices reflected immediately on the map.
The styling options described below are available for visualizing features according to time and date values.
Continuous Timeline (color)
If a layer contains date values, you can use color to view the data sequentially from new to old or before and after a key date. For example, applying a color ramp with the Before and after theme to the date attribute in the Rotterdam buildings feature layer can help you see which buildings were built or rebuilt after the Rotterdam Blitz.
To style dates using color to show a continuous timeline, do the following:
- Follow the first five steps of Apply a style. Choose an attribute field that contains date values.
- Click the Continuous Timeline (color) style and click Style options.
- Optionally, do any of the following:
- From the Theme drop-down menu, choose a theme for the color ramp. Each color theme can tell a different story by matching colors to data in different ways.
- Click the color ramp under Symbol style and choose a different color ramp, or change other graphic parameters such as stroke weights and colors, and define the applicable settings. For more information, see Use style options.
- In the Style options pane, click Invert color ramp
to invert, or flip, the colors in the color ramp. - Adjust the bounding handles along the color ramp to change how it is applied to the data. You can either drag the handle or click the date next to the handle and type a new date. Experiment with the position of the handles and use the histogram and calculated average information
to understand the distribution of the data to fine-tune the message of the map.Tip:
Click Magnify slider
to enlarge the details in the histogram. To return to the original slider positions at any time, click Reset slider positions 
. - Turn on the Show features with no values toggle button to draw locations with missing data on the map, and optionally specify a style and label to represent those values.
- Turn off the Include in legend toggle button to hide the color ramp in the legend.
- If you are mapping point symbols, you can rotate symbols based on a second numeric attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings. You can only use this option if you have numeric or date data associated with the locations. For example, if the layer contains sales data, you can adjust the transparency of each store proportionally to its revenue.
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.
Continuous Timeline (size)
If a layer contains date values, you can use a sequence of proportional symbols to view the dates sequentially on the map. For example, you can show where the oldest buildings in Rotterdam are located using larger symbols to represent older buildings and smaller symbols to represent newer buildings.
To style dates using proportional symbols to show a continuous timeline, do the following:
- Follow the first five steps of Apply a style. Choose an attribute field that contains date values.
- Click the Continuous Timeline (size) style and click Style options.
- Optionally, do any of the following:
- Click the color ramp under Symbol style and specify the applicable settings to change the styling of proportional symbols (color, stroke, opacity). For more information, see Use style options.
- Click Invert size ramp to invert, or flip, the symbol size order.
Note:
By default, recent dates are drawn with larger symbols and less recent dates are drawn with smaller symbols. Clicking Invert size ramp allows you to reverse this pattern.
- Adjust the bounding handles along the histogram to change how the proportional symbols are applied to the data. You can either drag the handle or click the date next to the handle and type a new date. All values above the upper handle are drawn with the same largest symbol. Values below the lower handle are displayed with the same smallest symbol. The remaining values are drawn with a proportional sequence of sizes between the two bounds. Experiment with the position of the handles and use the histogram to see the distribution of the data to fine-tune the message of the map.
Tip:
Click Magnify slider
to enlarge the details in the histogram. Click Reset slider positions to return to the original slider positions at any time. - For Size range, keep the default size range or specify a custom range (in pixels) by adjusting the slider handles or clicking the default values and entering new ones. Keep the Adjust size automatically check box checked to optimize the symbols for the current map zoom level and automatically adjust them at other zoom levels.
- If you are mapping data associated with polygons, click the Symbol style box and adjust the fill and stroke properties of the polygons. For more information, see Use style options.
Tip:
By default, polygon feature symbols in the layer—for example, county boundaries—are shown on the map under the proportional symbols. To keep this setting, leave the Show background symbol toggle button turned on and optionally customize the symbol style for the background features, such as adjusting the transparency or changing the outline color. To hide the background symbols in the layer—for example, if you don't want to see county boundaries under the proportional symbols—turn off the Show background symbol toggle button.
- Turn on the Show features with no values toggle button to draw locations with missing data on the map, and optionally specify a style and label to represent those values.
- Turn off the Include in legend toggle button to hide the size ramp in the legend.
- Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings. You can only use this option if you have numeric or date data associated with the locations. For example, if the layer contains sales data, you can adjust the transparency of each store proportional to its revenue.
- If you are mapping point symbols, you can rotate symbols based on a numeric or date attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.
Age (color)
If a layer contains date or time values, you can use color to represent the age of features. Age reflects the length of time (in seconds, minutes, hours, days, months, or years) from a start date or time to an end date or time. For example, you can use this style to show how long it took first responders to arrive at the scene of medical emergencies based on the time of the incident alarm (start time) and the time the responder arrived (end time).
To style dates using color to represent age, do the following:
- Follow the first five steps of Apply a style. Choose an attribute field that contains date values.
- Click the Age (color) style and click Style options.
- In the To section, do one of the following to specify an end date:
- Click Field to use the most recent date in the specified date field.
- Click Custom date, click the date box, and choose a custom date.
- Optionally, click Flip From and To to switch the start date to the end date.
- From the Units drop-down menu, select the time units.
- Optionally, do any of the following:
- From the Theme drop-down menu, choose a theme for the color ramp. Each color theme option can tell a different story by matching colors to the data in different ways.
- Click the color ramp under Symbol style to choose a different color ramp, or to change other graphic parameters such as stroke weights and colors, and define the appropriate settings. For more information, see Use style options.
- In the Style options pane, click Invert color ramp to invert, or flip, the colors in the color ramp.
- Adjust the bounding handles along the color ramp to change how the color ramp is applied to the data. You can either drag the handle or click the number next to the handle and type a precise value. Experiment with the position of the handles and use the histogram and calculated average information to understand the distribution of the data to fine-tune the message of the map.
Tip:
Click Magnify slider
to enlarge the details in the histogram. Click Reset slider positions to go back to the original slider positions at any time. - Turn on the Show features with no values toggle button to draw locations with missing data on the map, and optionally specify a style and label to represent those values.
- Turn off the Include in legend toggle button to hide the size ramp in the legend.
- Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings. You can only use this option if you have numeric or date data associated with the locations. For example, if the layer contains sales data, you can adjust the transparency of each store proportional to its revenue.
- If you are mapping point symbols, you can rotate symbols based on a numeric or date attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.
Age (size)
If a layer contains date or time values, you can use a sequence of proportional symbols to view the age of features. Age reflects the length of time (in seconds, minutes, hours, days, months, or years) from a start date or time to an end date or time. For example, to show the age of code violations from complaint date to compliance date, you can show violations that are less than 30 days old with a small symbol and use increasingly larger symbols for violations that are closer to 90 days old.
To style dates using proportional symbols to represent age, do the following:
- Follow the first five steps of Apply a style. Choose an attribute field that contains date values.
- Click the Age (size) style and click Style options.
- In the To section, do one of the following to specify an end date:
- Click Field to use the most recent date in the specified date field.
- Click Custom date, click the date box, and choose a custom date.
- Optionally, click Flip From and To to switch the start date to the end date.
- From the Units drop-down menu, select the time units.
- Optionally, do any of the following:
- Click the symbol under Symbol style and change the settings to change the styling of proportional symbols (color, stroke, opacity). For more information, see Use style options.
- Click Invert size ramp to invert, or flip, the symbol size order.
Note:
Older features are drawn with larger symbols and younger features are drawn with smaller symbols by default. Inverting the symbol size order allows you to reverse this pattern.
- Adjust the bounding handles along the histogram to change how the proportional symbols are applied to the data. You can either drag the handle or click the date next to the handle and type a new date. All values above the upper handle are drawn with the same largest symbol. Values below the lower handle are drawn with the same smallest symbol. The remaining values are drawn with a proportional sequence of sizes between the two bounds. Experiment with the position of the handles and use the histogram to see the distribution of the data to fine-tune the message of the map.
Tip:
Click Magnify slider
to enlarge the details in the histogram. Click Reset slider positions to return to the original slider positions at any time. - For Size range, keep the default size range or specify a custom range (in pixels) by adjusting the slider handles or clicking the default values and entering new values. Keep the Adjust size automatically check box checked to optimize the symbols for the current map zoom level and automatically adjust them at other zoom levels.
- If you are mapping data associated with polygons, click the symbol under Symbol style and adjust the fill and stroke properties of the polygons. For more information, see Use style options.
Tip:
By default, polygon feature symbols in the layer—for example, census tract boundaries—are shown on the map under the proportional symbols. To keep this setting, leave the Show background symbol toggle button turned on and optionally customize the symbol style for the background features, such as adjusting the transparency or changing the outline color. —Turn off the Show background symbol toggle button to hide the background symbols in the layer—for example, if you don't want to see census tract boundaries under the proportional symbols .
- Turn on the Show features with no values toggle button to draw locations with missing data on the map, and optionally specify a style and label to represent those values.
- Turn off the Include in legend toggle button to hide the size ramp in the legend.
- Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings. You can only use this option if you have numeric or date data associated with the locations. For example, if the layer contains sales data, you can adjust the transparency of each store proportional to its revenue.
- If you are mapping point symbols, you can rotate symbols based on a numeric or date attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.
Discrete Time Periods (categories)
If you have date or time attributes in a layer, you can show various categories representing discrete time periods. For example, you can use different colors to represent the year sewer lines were installed in 1885 and earlier in a city.
To style data using discrete time periods, do the following:
- Follow the first five steps of Apply a style. Choose an attribute that contains date values.
- Click Discrete Time Periods (categories) and click Style options.
- Optionally, do any of the following:
- Click the symbol under Symbol style to change all the map symbols at once, and specify the symbol options, such as a different color ramp or fill transparency. For more information, see Use style options.
- Click the colored symbol next to each category in the list to customize categories individually. Available styling options for each kind of symbol are shown depending on whether the data is points, lines, or areas. For example, if the data is points, you can change the symbol shape, fill color, and outline.
- Drag a category up or down in the list.
- For best visualization, include fewer than 10 categories in a layer. More than 10 are difficult to distinguish by color alone. If you include more than 10, only the 10 with the highest counts are shown. The remainder are automatically grouped into the Other category. If the counts of features can't be determined, the first 9 categories are listed individually in alphabetical order, and the rest are grouped in the Other category. To ungroup these observations one at a time, drag them out of the Other list and into the main list, or click Move value out. To ungroup all of these observations at the same time, click Move all values out. To hide features in the Other category, uncheck the box. To show them, keep the box checked.
- Click Transparency by attribute and specify the transparency settings to adjust the transparency of discrete time periods per feature. You can only use this option if you have numeric or date data associated with the locations. For example, if the layer contains restaurant sales data, you can style the data according to the type of restaurant and adjust the transparency of each category proportionally to its annual sales.
- If you are mapping point symbols, you can rotate symbols based on a numeric attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.
Color (age) and Size and Color and Size (age)
You can use these styles to show two attributes on a map using color and proportional symbols to see the age of features in the data. Age reflects the length of time (in seconds, minutes, hours, days, months, or years) from a start date or time to an end date or time. You can use the Color (age) and Size or Color and Size (age) style when you choose one date attribute and one numeric attribute or two date attributes.
One date and one numeric attribute
You can use color to show the age of features and use proportional symbols to represent the numeric attribute values. Choose the date attribute as the first attribute and the numeric attribute as the second attribute, and select the Color (age) and Size style. Alternatively, use proportional symbols to represent the age of features and use color to represent the numeric attributes by switching the order of the selected attributes and choosing the Color and Size (age) style.
For example, you can use the Color (age) and Size style to map traffic accidents, with color showing where the most recent accidents occurred based on the accident date, and proportional symbols showing how many vehicles were involved.
You can use the Color and Size (age) style when mapping storm water structures by using color to show the depth of the structures and size to show how long ago the inspections occurred based on the inspection date. See an
To style one date attribute and one numeric attribute to show age, do the following:
- Follow the first five steps of Apply a style.
For mapping styles that show the age of features, choose at least one attribute that contains date values. The other attribute can contain date values or numeric values.
- Repeat the previous step to select a second attribute or an Arcade expression.
The available age options depend on the order of attributes you chose and whether you chose one date attribute and one numeric attribute or two date attributes. To switch the order of the attributes, drag the second attribute to the top of the attribute list.
- Click an age style and click Style options.
- Apply the options for either of the following combinations: Age (color) and Counts and Amounts (size) or Counts and Amounts (color) and Age (size).
Two date attributes
If you choose two date attributes, you can use color or proportional symbols to show the age of features based on one of the date attributes. A continuous timeline based on the other date attribute is shown using the other rendering option (color or size). You can also choose the same date attribute twice to show both age and a continuous timeline based on that same attribute.
The Color (age) and Size style uses color to represent age based on the first date attribute and uses proportional symbols to represent dates as a continuous timeline based on the second date attribute. For example, on a map showing storm water structures, you can use color to show the age of the structures based on their construction date, and use larger symbols to emphasize structures that have older inspection dates. See an
The Color and Size (age) style does the opposite of Color (age) and Size, using color for the continuous timeline and proportional symbols for the age of features. For example, on a map showing city code violations, you can use color to show complaint dates as a continuous timeline from older complaints to newer complaints, and use larger symbols to emphasize code violations that have gone uncorrected for a significant amount of time. See an
To style two date attributes to show age, do the following:
- Follow the first five steps of Apply a style.
For mapping styles that show the age of features, choose at least one attribute that contains date values. The other attribute can contain date values or numeric values.
- Repeat the previous step to select a second attribute or an Arcade expression.
The available age options depend on the order of attributes you chose and whether you chose one date attribute and one numeric attribute or two date attributes. To switch the order of the attributes, drag the second attribute to the top of the attribute list.
- Click an age style and click Style options.
- Apply options for either of the following combinations: Age (color) and Continuous Timeline (size) or Continuous Timeline (color) and Age (size).
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.
Types and Size (age)
If a layer contains unique values (types) and date or time values, you can use color to show various categories, or types, of features based on the unique values, and proportional symbols to show the age of features. Age reflects the length of time (in seconds, minutes, hours, days, months, or years) from a start date or time to an end date or time. For example, in a map showing sewer lines by type, you can use a different color to represent each type and different-sized symbols to show how many years ago they were installed.
To style two attributes using color to show different types and proportional symbols to show age, do the following:
- Follow the first five steps of Apply a style. Choose an attribute that contains date values.
- Repeat the previous step to select a second attribute. Choose an attribute that contains unique values.
- Click the Types and Size (age) style and click Style options.
- Apply options to Types (unique symbols) for the first attribute and Age (size) for the second attribute.
- Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.