Roadway data are fundamental to GIS-T and many of the most important transportation modes (e.g. highway, transit, bike). Many GIS functions and analyses rely on it including geocoding and network analysis, both of which we’ll take a close look at in the next few lessons. Roadway data also play an important role in mapping and visualization for many GIS applications.
There are a number of commercial and public sources of street data and services which are available. Some are public and freely available, and others are commercial. In this lesson, we’ll take a look at some of the most widely used sources of street data.
TIGER is a data source produced and published by the U.S. Census Bureau. These data include street data which can be used to perform geocoding or to produce a street network. TIGER data were used as a “seed” for many of the other roadway data sources, both public and commercial. We will take a closer look at TIGER data later in this section.
OSM is a rapidly growing Volunteered Geographic Information (VGI) project which got its start in 2004 and is sponsored by the OpenStreetMap Foundation. For U.S. roads, OSM initially used TIGER Line files but many updates have since been made based on input from its volunteer community which is now over a million strong. In some parts of the world, OSM data are as good, or nearly as good, as its commercial counterparts.
State-level transportation agencies have long maintained road centerline networks as well as additional networks for other modes. They have been improved greatly in accuracy and precision, and agencies are increasingly adding local and private roads and associated data. Much of this latter impetus is due to increased federal requirements for data collection and reporting. In most cases, these networks are the most complete and accurate product for network features and associated attributes for any given state.
Transportation for the Nation (TFTN)
TFTN is an evolving governmental initiative from the National States Geographic Information Council (NSGIC) and USDOT that originated in 2008. TFTN will initially be a road centerline dataset that may replace overlapping federal efforts and products. A set of centerline datasets has been created as part of state DOT submittal requirements for FHWA’s Highway Performance Monitoring System (HPMS). The next step is to try and join these across state lines.
TomTom / Tele Atlas
Tele Atlas was founded in 1984 and was acquired by TomTom in 2008. Tele Atlas data was primarily collected from its own mapping vans. The company’s road products are decreasing in importance and usage.
Nokia / NAVTEQ / HERE
Founded in 1985 and acquired by Nokia in 1991, NAVTEQ (now renamed HERE) operates independently and partners with third-party agencies and companies to provide its networks and services for portable GPS devices made by Garmin and others, and Web-based applications including Yahoo! Maps, Bing Maps, Nokia Maps, and MapQuest.
ESRI StreetMap and StreetMap Premium
ESRI does not produce road data directly but instead acquires it from HERE, TomTom, and others and repackages it. ESRI StreetMap covers North America and is part of Data and Maps which is included with ArcGIS. StreetMap premium has more current data than StreetMap and also has coverage for Europe.
Google has become a major provider of mapping services. Google doesn’t make its street data available directly but instead uses it to provide services. These services are provided through products such as Google Maps, Google Earth, and various APIs. In 2008, Google released a tool called Google Map Maker to encourage individuals to submit or correct feature information. This is similar in concept to the manner in which OSM derives much of its data. Google retired Map Maker in 2017 in favor of its "Local Guides" program. As a "Local Guide," you can contribute reviews of businesses or places, upload photos and suggest a new place. Recently, they also began to add capabilities to allow users to report issues with roadway geometry and missing roads. Local Guide contributions are all made directly in the Google Maps interface. Take a look at these comparisons between OSM and Google in regards to the services they provide and their user contributions programs. One should note these comparisons are published on the OSM Wiki site so they may be a bit biased.
Also, check out this map comparison tool made available by Geofabrik, an organization who promotes OSM and provides a portal for downloading OSM data extracts. Select an area you are familiar with, and compare the OSM map, the Google map, and the HERE map.
Assignment 2-1 (15 points)
Complete the following tasks:
- Watch this presentation on Google’s Ground Truth Project. Please allow 40 minutes to view the entire video.
- Explore and compare the tools which Google makes available for Local Guides through Google Maps with the iD editor OSM makes available to its volunteers directly through the OSM site. To become a Local Guide, you'll need to create a Google account if you don’t already have one. Similarly, to become an OSM contributor, you'll need to sign up for an account (upper right corner of the main page of their site). To familiarize yourself with how the iD editor works, complete the walkthrough. (Note: You're asked if you want to complete the walkthrough the first time you launch the editor. In addition, you can access the walkthrough anytime you're using the iD editor by pressing "H" on your keyboard.)
- There are many editors available for OSM, one of the most popular of which is called the Java OpenStreetMaps editor (JOSM). Skim through the learning guide for JOSM to familiarize yourself with its capabilities.
Submit a write-up in M.S. Word format (no more than 500 words) to Assignment 2-1 in Canvas which addresses the following items:
- What do you find most interesting about Google's processes for collecting and correcting the data it displays on its maps and uses to support the other services it provides? (3 points)
- Compare Google's Local Guides tools with OSM's iD editor in terms of capabilities and ease of use. (4 points)
- The Map Maker tool, which Google retired, was demoed a bit in the Ground Truth video. How do you think the current capabilities of the Local Guides tools in Google Maps compare to the capabilities which Map Maker offered? (3 points)
- What are some of the fundamental differences between OSM's iD editor and JOSM? (3 points)
- If you were to contribute some of your time to improving Google maps or OSM, which would you choose and why? (2 points)
Exploring TIGER and OSM Data
In this section, we'll take a closer look at two of the most extensive sources of publicly available roadway data: TIGER and OSM.
The TIGER database was first created in preparation for the 1990 decennial census. In creating TIGER, not only did the Census Bureau produce the first nationwide map of roadways, it also incorporated topographical context which defined the relationship between road features as indicated in its name: Topologically Integrated Geographic Encoding and Referencing database.
In addition to the TIGER spatial database, the Census Bureau also created a Master Address File (MAF) which is a database of all known living quarters in the U.S. The MAF contains about 300,000 addresses which are identified as location addresses, mailing addresses or both. In addition, the MAF contains a record for each living unit which can correspond to a separate structure or a residence within a shared structure. There are about 200,000 living units in the MAF some of which have multiple associated addresses. Following the 2000 decennial census, the Census Bureau decided to merge the two databases into a single database known as the MAF/TIGER Database (MTdb).
The Census Bureau is planning a 3-part informational series on TIGER to commemorate its 25th anniversary. Part 1 will examine the history of TIGER, Part 2 will address efforts to improve its accuracy, and Part 3 will address the tools which provide access to the data. To date, only Part 1 of the series has been made available. Spend a few minutes looking through the document to learn a little about TIGER’s history.
The TIGER data is available in a number of formats including Shapefiles, geodatabases, and KML files. The Census Bureau also provides a tool called TIGERweb which allow online viewing and the ability to incorporate TIGER data directly in GIS applications via web services including an OGC standard Web Mapping Service (WMS). For the exercises in this and the upcoming lesson, we will be working with the TIGER/Line shapefiles.
The Tiger/Line shapefiles are available for multiple years. Each year, the Census Bureau provides an updated set of Tiger/Line shapefiles in addition to associated technical documentation. The technical documentation for the 2017 Tiger/Line shapefiles can be found here. It is over 120 pages long and serves as an excellent reference for the Tiger/Line Shapefiles.
With more than 3 million registered users, the OSM project has a huge community behind it. Consequently, there is plenty of documentation available for learning about the project and becoming a member of the community. A few good resources for learning about OSM are the Open Street Map Wiki and the guides on LearnOSM.org.
OSM data is natively available in a unique file format (i.e., .osm files). However, many of the sites which provide access to OSM data serve it up in commonly used formats like shapefiles. For example, take a look at Geofabrik’s OSM data download page. Also, take a look at the first few sections of the OSM Data Guide which describe the .osm file format and some options for acquiring OSM data.
We often talk about spatial data in terms of points, lines, polygons, and attributes. OSM, however, uses the terms nodes, ways, relations and tags. In order to develop some understanding of these terms, take a look the descriptions of OSM data’s elements on the OSM Wiki site.
Assignment 2-2 (20 points)
Complete the following tasks:
- Review Section 2 and Section 3.12 of the technical documentation for the 2017 TIGER/Line Shapefiles.
- Download the 2017 TIGER/Line All Roads shapefile for Centre County, Pennsylvania.
- Download the latest OSM data for Pennsylvania from Geofabrik and review Geofabrik's documentation on the features included in the download.
- Watch the first 15 minutes of the presentation OSM and Government: What You Need to Know About TIGER where Stephen Johnson discusses the relationship between OSM and TIGER.
Submit a write-up in M.S. Word format (no more than 500 words) to Assignment 2-2 in Canvas which addresses the following items:
- How do the OSM terms nodes, ways, relations, and tags relate to points, lines, polygons, and attributes? (4 points)
- If you downloaded the 2015 All_Roads layer for a fictitious county (FIPS code =42079) from TIGER, what would the name of the shapefile be? (note: assume a file extension of .shp)(1 point)
- What are the coordinate systems for the TIGER/Line shapefiles and the Geofabrik OSM shapefiles? (1 point)
- Use ArcMap to compare the Roads feature class downloaded from OSM for Pennsylvania with the All Roads features you downloaded from TIGER for Centre County. Focusing on the Centre County region, list some similarities and differences between the two in both spatial characteristics and attributes. Include screenshots to support your observations. (6 points)
- Describe the differences between the TIGER/Line All Lines shapefile and the All Roads shapefile. Why isn't the TIGER/Line ID (TLID) found in the All Roads shapefile? (4 points)
- In general terms, not in terms of the limited datasets downloaded above, describe the relationship between TIGER and OSM. Which data source came first? What is the difference in geographic scope? What do you think the ongoing relationship should be? (4 points)