Merging Two North American Street Databases

Over the last 20 years, Geographic Data Technology (GDT) has worked diligently to employ a sound business model for change detection, and refined their ISO-certified production processes to ensure consistent data delivery with the highest level of quality.With the Tele Atlas / GDT merger in 2004, the change detection and management process was refined and improved further by adding a field survey and validation team to the process.The combination of these two processes means more accurate data, and the release of a very comprehensive product.This is important to us at MapInfo because our users demand the very best street data.

MapInfo StreetPro "" Benefiting from a Powerful Synergy of Data
Web services.Service oriented architecture.Business intelligence. Dashboards.All of these applications are designed to serve up data so that intelligent business decisions can be made.But they don't address one fact "" that data is the key to the intelligent decision.No matter how informative the display, the decision is only as good as the data on which it is based.

Combining Two Centerline Network Databases "" What did it Entail?
At the time of the acquisition, both data providers had comprehensive North American databases of street data based on years of data collection.Tele Atlas has spent more than a year merging the two databases into one.This required comparing the databases in detail and identifying and reconciling differences on a segment-by-segment basis. The process included the following:

Tele Atlas and GDT each had about 4.8 million miles of streets with the same information (e.g., overlapping data that agreed completely)
GDT had an additional 1.3 million miles of data not contained in the original Tele Atlas database; and
Tele Atlas had an additional 600,000 miles of data not in the original GDT database

In parallel with the integration process, day-to-day operations have continued uninterrupted.For example, from April 2004 "" September 2005 during the database comparison and integration process, there have been:

More than 62.5 million automated edits
More than 19.5 million manual edits
More than 4.2 million miles of roads have been driven
More than 1 million miles of new geometry added; and
Nearly 310,000 miles of streets aligned to 12 meter accuracy or better

A "Best of Both Worlds" Methodology
Historically, Tele Atlas and GDT used two different methodologies to build their products and deliver them to market.Both of these methodologies had their strengths.

The Tele Atlas Field Survey and Validation team concentrated on driving the streets to collect new data and verify existing information and reported changes.This approach helps guarantee accuracy, but is not enough to make sure you capture all the changes.With over 8 million miles of roadways in North America, it would require a fleet of 500-1,000 vehicles driving every day to cover all the roads in one year.Obviously, driving the roads is not enough.In some ways, a model that relies on driving-only as a change detection methodology is "brute force," haphazard, and not cost-effective.

Conversely, the GDT method specialized in compiling data acquired from over 35,000 government and other 3rd party, authoritative sources throughout North America.This extensive network monitors and documents all changes and additions to streets in both the U.S.and Canada, and on average, delivers 15 million+ changes and updates per quarter. Combining these two methodologies provides the opportunity to generate a remarkably accurate and up-to-date street data.

An example of the types of geometry updates performed.(Click for larger image)

Going forward, Tele Atlas is leveraging the compilation method to detect change, conduct gap analysis and identify changed geographic areas.Where needed, the field survey teams can be deployed to validate data or collect missing data.This helps target the best areas for data gathering using the "drive the roads" method.By combining these two collection models, Tele Atlas is ensuring a complete database for customers who depend on the most accurate and up-to-date street information.