Creating Base Maps With ArcGIS Pro

Base maps are reference maps used behind thematic maps to provide geographic context. While some thematic maps (like world or national-level maps) show areas that are recognizable by most users simply by their shape, state and local maps often need some detail in a base map so users can get a better sense of where the different areas are located in the real world. In addition, point maps and some line maps at all scales generally need base maps to avoid looking like a random collection of geometric shapes hanging in space.

The Topographic Base Map in ArcGIS Pro

A variety of base maps from ArcGIS Online are available for usse in ArcGIS Pro. However, these base maps are general-purpose, low-resolution maps designed for use with web maps, and there may be situations where you need to create your own base maps:

This tutorial covers the steps for creating a base map, which are similar to those for creating a thematic map:

  1. Start the Map: Create a new project or add a map to an existing project
  2. Add the Thematic Features: Create a draft map over a standard base map so you can determine what is needed in the base map
  3. Add the Reference Features: Transportation lines, political boundaries, environmental features, places of reference
  4. Symbolize the Features: Create descriptive, clear, aesthetically-pleasing symbology and labeling
  5. Symbolize and Label the Features: Create descriptive, clear, aesthetically-pleasing symbology and labeling
  6. Present the Map: Create print layouts and / or publish as a reusable feature service
  7. Save Your Project: Save a project package to ArcGIS Online

Start the Map

To create a new map in a new project:

  1. Log in to ArcGIS Pro.
  2. When presented with options on the start screen, start your new project with a Map.
  3. Give the project a meaningful title so you can keep track of what is in different projects.
Starting a New Project

Add the Thematic Features

For this tutorial, we will use two example data sets to demonstrate different options for base map styling.

The example area data will be county-level electoral results for the 2012 US presidential election from the Minn 2016 Electoral Counties feature service from the University of Illinois ArcGIS Online organization.

The example point data will be a list of trauma centers from the Oak Ridge National Laboratories, that is distributed as a CSV file by the US Department of Homeland Security.

A trauma center is a hospital emergency room specially staffed and equipped to handle extreme life-threatening injuries like vehicle accident injuries, weapons injuries, major burns, etc. They are ranked in levels from I to V, with level I trauma centers being comprehensive regional facilities, with decreasing levels of capabilities down to level V centers that typically only stabilize patients before transfer to a higher-level center. (American Trauma Society 2020).

Adding Thematic Feature Layers

Add the Reference Features

A base map includes reference features that give geographic context for the thematic features and help map users understand where the thematic features are located in the real world.

Political Boundaries

Political boundaries define the extent of different governmental jurisdictions. In the United States, the general hierarchy of political boundaries from largest to smallest isis:

The source for political boundaries in these examples is the TIGER Cartographic Boundary Files, maintained and distributed by the US Census Bureau. The cartographic boundary files are, as the name implies, designed for mapping and may not correspond with the exact legal juristidictions.

For a map like this example of central Illinois which covers the region of a state, the state, county, and city (place) boundaries are probably most appropriate.

Adding Data For Political Boundaries

Transportation Routes

Because we experience and interact with the real world via modes of transportation, roads are excellent reference elements, and can also aid in navigation if a user wants to travel to experience one of the areas specified in the thematic features.

The source for reference features in these examples is the TIGER / Line Shapefiles maintained and distributed by the US Census Bureau. Note that this is a different set of files from the cartographic boundary files.

Adding a Roads Layer

Hydrographic Features

Hydrographic features (rivers, lakes, and other bodies of water) are notable features of many communities that often give points of reference, and also affect the routes people choose to travel. Accordingly, they can be useful features on base maps.

The US Geological Survey (USGS) maintains The National Hydrography Dataset (NHD), which "represents the water drainage network of the United States with features such as rivers, streams, canals, lakes, ponds, coastline, dams, and streamgages." Because this dataset is so detailed, the USCB downloads are for individual counties. However, the USGS provides a feature service that can be added to a map. While this is a scale-dependent service that will not show features statewide, it is useful for smaller areas.

Adding a Hydrographic Features Layer

Symbolize the Reference Features

Visual Hierarchy

Symbology choices define a visual hierarchy that focuses the viewer's eye on what is most and least important on the map. This visual hierarchy is created through differences in visual weight created using size, thickness, color, and drawing order.

The definition of what is important is dependent upon the purpose of the map and the intended audience. For the map of level I trauma centers, if the audience is regional planners and / or public health officials who are assessing availability of trauma services to residents in Central Illinois. In that case, a visual hierarchy from most to least important could be:

For the map of county election results, a potential audience could be political activists or operatives in an area who need historical information on past election results that will guide them on where to target limited resources in future campaigns. The visual hierarchy would be similar, although the county borders are part of the thematic symbols and do not need to be a separate layer.

Political Boundaries

The thickness and/or color of the lines specifying political boundaries should reflect their level of importance in the visual hierarchy. When mapping multiple levels of political boundaries, consider aligning the visual hierarchy with the political hierarchy.

When areas need to be higher in the visual hiearchy, you should consider using light, low-saturation fills to accent them. This technique may be more useful for point maps than area maps, where the shading will conflict.

For this example:

Symbolizing Political Boundaries

Transportation Features

Transportation features are often the most directly experienced and directly relevant features to map users. Accordingly, they should sit fairly high in the visual hierarchy, and should sit fairly high in the order of layers.

There are some commonly used line types for roads that are given as symbology options in ArcGIS Pro. You should probably use these options as fully as possible unless there is some reason to make other choices - such as the need for a low-detail base map that will not conflict with highly-detailed thematic layer(s).

  1. Within roads, there is also a hierarchy. In this particular TIGER dataset, the MTFCC parameter has two values: S1100 for interstates and S1200 for secondary highways. By symbolizing on this parameter, we can symbolize primary and secondary roads differently.
  2. For S1100 interstates we use a red limited access highway symbol that clearly stands out over the white background. Since this is a base map rather than a thematic road map, reducing the width to 2pt reduces the visual weight.
  3. For S1200 interstates we use a beige highway symbol that stands out over the white background and has less weight than the interstates, but more weight than the county lines. Again, 2pt width reduces the weight.
  4. The interstates should be drawn over any intersecting highways because the interstates are higher in the higherarchy. Selecting Symbology -> Symbol Layer Drawing and turn on Enable symbol layer drawing will make sure the items that are higher in the list of symbols will be drawn over lower items.
  5. Reducing transparency can also reduce the saturation and increase lightness so the roads do not dominate the visual hierarchy.
Symbolizing Transportation Features

Label the Reference Features

County Labels

In this hierarchy, county labels are low on the visual hierarchy and their visibility is not of great importance. To reduce conflict with other symbols and labels, the names labels labels are left black, but colored with 75% transparency so the more-important features will be visible under them.

County Names

City Labels

There are a large number of small towns in Illinois, and labeling them all would make the map impossibly cluttered.

To label only features that meet certain criteria, select the labeled layer in the Contents pane, select the Labeling, and click the SQL icon on the left side of the pane. Here you can define conditions for which features get labeled. To label only physically large cities, we label only areas where ALAND (size of the city) is greater or equal to 30,000,000 square meters. The optimum value will be dependent on the particular area being mapped and the amount of detail desired by the cartographer.

The labels should be symbolized with a white Halo that will reduce conflict with features underneath the labels.

Although not demonstrated in this video, if you need to delete unneeded labels or move labels around, you can Convert Labels to Annotations to create an annotation layer.

City Names

Road Labels

Transportation features can be difficult to label because roads are often dense (causing label collisions), are represented in segments (causing redundant labels), and may not have name attributes that are too long for concise labeling.

By selecting the road layer and the Labeling ribbon tab, you have access to options to automatically adjust the labels.

Highway Labels

Symbolize the Thematic Features

Once you have basic styling of your base map, you can add the thematic features and adjust the symbology so that the features are clearly visible over (and contextualized by) the base map information (figure-ground relationship), and so the visual hierarchy best suits the purpose for the map.

Point Thematic Symbols

Thematic features are generally considered the at the top of the visual hierarchy in a thematic map. Accordingly, they are also usually layered on top of the base map features.

Symbolizing Thematic Point Features

Area Thematic Symbols

Because thematic areas are often inherently large and less detailed that base map features, there may be occasions where thematic areas should sit under the base map features. You may then need to adjust the base map feature symbology and/or the thematic area symbology to match the desired visual hierarchy.

Symbolizing Thematic Area Features

Present the Map

Publish the Base Map As a Feature Service

If you plan to reuse your base map in the future, and especially if you want to share your base map with other users in other projects, you might consider publishing your base map as a web layer.

Remove all the thematic symbol layers and any unused layers before publishing.

One issue that may arise is that some of the more complex symbology and labeling options (like complex road symbols, highway label shields, and custom symbol layer line drawing order) cannot be saved to feature layers. You will be notified with warnings when you analyize your map before sharing, and you can ignore these warnings if simplification of your symbols will not be a problem for you.

Publishing a User-Created Layer

Figure Layout

Once we have gotten the map content the way we want it, we create a new Layout that will allow us to design how the map will look when inserted into a document as a figure.

Map Figure Layout

Standalone Print Layout

You can also create print layouts that are ready to print directly. Cartographic convention dictates adding some additional marginalia information to the margins of printable maps.

Laying Out a Standalone Map

Save Your Project

Saving a Project Package

When you are done with a project, you should save it as a project package on ArcGIS Online:

Saving a Project Package to ArcGIS Online

Reopen a Project Package

Reopening a Project From a Project Package