Finding and Using GIS Data

What is a Web Service?

As more GIS data and functionality moves online, it has become increasingly common for data providers to offer web services. Rather than a more traditional client/server method, where data is downloaded onto a computer from an online portal, a web service allows users to connect to data hosted in real time. In other words, it leverages the web to provide not only data, but also a degree of functionality found in a GIS. Users can turn layers on and off, customize symbology, and perform queries as if they were using a desktop GIS software. Advantages to this method include:

• Providers constantly maintain data and push through updates over the web. This ensures the data is always current and does not require re-downloading for every update.
• There is no need to download the data to a computer. This is especially handy for large datasets, such as aerial photography, because it saves storage space.
• ArcGIS Pro has the ability to connect to web services, so a hosted dataset can be imported into Pro should a user require a more sophisticated analysis.

Both the city of Milwaukee and Milwaukee County have GIS web services (also known as "service endpoints") covering a variety of topics, including current and historical planimetric maps, current and historical aerial imagery, utilities, topographic maps, and parcel data. Additionally, ESRI's Living Atlas of the World is an excellent source of worldwide GIS data hosted as a web service.

How do I access Web Services?

While each organization has a different interface for accessing their web services, they typically share a common platform in ESRI's Representational State Transfer (REST) endpoint catalog. Here, a user scrolls through a list of broad subjects to narrow down their search for a specific dataset(s). Upon finding them, the user can open it up in ESRI's suite of GIS products, such as ArcGIS Online or ArcGIS Pro. Below are some general steps to follow for accessing a data provider's web services.

1. Go to the data portal's homepage and look for language indicating "GIS Web Services" or "GIS Service Endpoints." If you're having trouble finding this, go to a search engine and type in "[name of organization] gis web service endpoints".

2. Upon locating the webpage for the organization's web services, there is typically a link to the actual REST catalog. Sometimes, the link's title will include "REST", but other times it may not. In this case, it will usually say "Map Service Endpoints", "GIS Service Endpoints", or something to that effect. When found, click the link.

3. A new tab will automatically open and the page will appear similar to the image shown below. Remember, each data provider will have a different list of subject categories.

4. Click the desired subject category to get more refined subjects, then click one of those subjects to view the actual datasets. Example: DPW > Streetcar.

5. Towards the top of the page of the refined subject category ("Streetcar" in the above example), next to "View In:", there is a list of ESRI applications in which the data can be opened. Click your preferred application.

City of Milwaukee GIS Web Services

Map Milwaukee's GIS Web Services page connects users to data hosted on the web. There is no need to download the data onto your computer, and the data are regularly maintained and updated by the city. For example, a user can pull U.S. Census data from the web service and create a custom webmap in ArcGIS Online. For large-sized files, the web service method can save a lot of storage space compared to the more traditional client/server method.

Note: The above link provides related information beyond the actual data. Click "Link to REST endpoint for all services" in the GIS Web Services homepage to view the datasets themselves.

Available Data Include:

• Neighborhoods and opportunity zones
• Schools and school board districts
• Property assessments
• Census data, including 2010 decennial census and ACS five-year averages
• Department of Public Works (DPW): Forestry; operations; sanitation; streetcar; parking meters; paving program
• Environmental Collaboration Office (ECO): Basement backups by year; green infrastructure; DPW basement connection areas
• Milwaukee Metropolitan Sewerage District: Watersheds; sub-basins; combined sewer area; total impervious areas; constraints
• Elections: Aldermanic districts; polling places; voting wards; county supervisor districts; state senate & assembly districts; U.S. Congressional districts
• GeoEventFleet, which helps DPW track its vehicles
• Locator
• Milwaukee Fire Department (MFD): Stations; areas of responsibility; community outreach
• Milwaukee Police Department (MPD): Crime; districts; reporting districts; squad areas; stations; various layers for GIS use
• Planning: FEMA floodways, Special Flood Hazard Areas, & market value analysis; DCD special districts; Targeted Investment Neighborhoods; historic preservation sites; Community Development Grants Administration; zoning
• Properties/parcels
• Reference maps
• Community living arrangement facilities
• Licensed locations for various types of businesses
• Strong Neighborhoods Plan
• Utilities: Various layers that support geoprocessing and geocoding within online mapping software

For complete documentation of Map Milwaukee GIS Web Services, see https://city.milwaukee.gov/ImageLibrary/Public/GIS/MapMilwaukee_Services_20201.pdf.

See our "How To: Web Services" page for information about using web services.