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Mobile mapping … cutting-edge technology for the development of digital maps
Arnout Desmet
Director - Asia-Pacific, Middle-East & Africa - New Markets
Moutstraat 132
B-9000 Gent
BELGIUM
Tel.: +32 9 244 88 97, Fax.: +32 9 222 74 12
Email: arnout.desmet@teleatlas.com
Introduction
Mobile mapping is a cutting edge technology applied by Tele Atlas to meet the challenge of gathering constantly changing road data rapidly and precisely. Vehicles equipped with digital cameras, installed in stereoscopic pair(s), as well as additional sensors for highly accurate positioning, capture real-world by driving the extensive road network in Europe.
The content-rich information that is gathered by the mobile mapping vans is sent to the Tele Atlas production centre, where over 500 digital cartographers use it to update and enrich the Tele Atlas databases. As the information can be gathered far more rapidly this way than by traditional survey methods, the databases are updated more frequently, thus providing customers with a more accurate database that is also more detailed.
Tele Atlas first tested this approach in the 1980s. The subsequent development of digital imaging technology, accurate GPS systems, inertial measurement unit positioning and digital mass storage have enabled it to become much more effective and turn mobile mapping in a practical reality that is now changing the world of digital mapping. As part of its programme to maintain outstanding quality, Tele Atlas has invested in more than 20 mobile mapping vehicles for its operations in Europe and in training a dedicated development and production team at the Tele Atlas production centre in India.
The accuracy and up-to-datedness of mobile mapping is contributing significantly to the effectiveness of advanced applications such as Advanced Driver Assistance Systems (ADAS ) and 3-D mapping.
Basic definition & description
The term mobile mapping in general is used as the technology to map and verify map data in the field. In this case, the definition of mobile mapping is used in a more strict sense as follows: Mobile mapping represents a heterogeneous type of sensor integration consisting of navigation sensors as well as imaging sensors, together time synchronized and mounted on a common platform (Schwarz & El-Sheimy, 1996).
Description of the mobile mapping system
The mobile mapping system (MMS) used within Tele Atlas has the digital cameras mounted on a vehicle (van). At least two of the digital cameras are installed in stereoscopic pair, spaced apart so that the combined image can provide 3-dimensional information. The capturing speed of the images is linked to the speed of the vehicle up to 3 images per second to obtain a complete recording of the information along the road network.
Figure 1: Mobile Mapping van
The picture resolution which is used per camera is typically 1200 * 960. Although higher resolution cameras can be mounted, this resolution was experienced as a good balance between data-storage requirements and features and attributes to be recognized.
The camera configuration used is typically between 4-6 (2 forward, 2 right side, 1 back-ward and 1 left side looking camera), depending on the roads types to be surveyed.
Figure 2: Various camera configurations - Mobile Mapping van
With these configurations, >95% of the visual components of the required objects/features can be recognized. Specifically for house-numbers and street name signs, the accuracy is lower and specific camera mounting is needed per country and per situation.
The positioning devices calculate the co-ordinates of a specific point on the vehicle. Following positioning sensors are included:
To handle the high incoming data stream, 1-4 PC's (one PC is linked to 2 cameras) are mounted in the back of the van, including UPS back-up facilities.
Figure 3: Front & rear view of the MMS equipment mounted in the mobile mapping van
The back-end of the mobile mapping system is an in-house processing unit that allows the visualisation of the imagery. It also allows photogrammetric measurements of objects on the images and the linking of the images and measurements to map data.
The Tele Atlas Mobile Mapping System (MMS) consists of two main components:
Description of the mobile mapping process
The MMS vehicle is used in field to gather
Because of the high reliability and data stream demand, the MMS vehicle is only used for basic data streaming and data interpretation of positional information & camera frames. More sophisticated algorithms are handled in post-processing tools.
This approach gives the following advantages:
What do we capture on basis of mobile mapping?
The databases created and maintained by Tele Atlas are used for route calculation, route guidance, turn-by-turn navigation and other geospatial applications. They contain particular map features and attributes.
There are five main categories of features and attributes:
The imagery materials collected by the MMS do provide to a large extent the necessary reference material to create and/or maintain the features and attributes referred to above as illustrated in some example imagery in figure 4 below.
Figure 4: Examples of high quality images collected by means of Mobile Mapping
Advantages of mobile mapping
The speed of capturing the imagery is the average driving speed on the roads and is not a function of the complexity to be mapped or verified. It is only a function of the traffic and the speed-limits. These driving speeds are therefore not limited to the interpretation-speed of a cartographer (since this is done in a post process). The frequency of verification of the real world can be up to 7 times higher versus traditional field verification methods, substantially increasing up-to-dateness and shortening the time-to-market.
A second major advantage of the mobile mapping process is that the system records the real world situation before the interpretation is done (from several angles). The approach overcomes the naturally limited performance of a human surveyor by shifting specific data collection and inspection activities to the office environment where human and computer resources can be optimally applied. Since we store reality in our imagery archive instead of recorded change detection of that reality, the real-world situation can be traced back and verified before an interpretation is done. This is a major advantage for the verification of the quality of the captured information, but it is also very useful to verify defect reports provided by customers.
One of the key benefits is that the data interpretation and the data processing are combined in one location, and executed with resources independent from the data collection activities. While the combination of data interpretation and data processing allows better quality, further improvements are realised by doing this interpretation of reality in-office and not under the strain of real traffic and the limited circumstances of the vehicle. Owing to the high speed capturing, benefits on product level can only be reaped when sufficient processing resources are at hand. Our large-scale production facilities offer us this advantage.
Because the position and orientation log of the MMS can be combined with the visual interpretation of lanes on the images, the system allows an accurate positioning and verification of road centrelines better than 1m positional accuracy (1s) and 2m (2s) (95% of all positional measurements have maximum deviation of 2m). The positional accuracy is also illustrated in the figure below comparing MMS logs with high-resolution georeferenced imagery.
Figure 5: MMS positional accuracy versus high resolution imagery
A major advantage of the mobile mapping process is that the captured high resolution ground images provide a geo-referenced source of new content which can be extracted in the production units at the required moment. The source is accurate, independent of interpretations and quality
Further information about Tele Atlas
Founded in 1984, Tele Atlas is a worldwide leading provider of digital maps and dynamic location content for a variety of navigation, location-based services and geospatial products and database solutions. Tele Atlas' database is a highly accurate reproduction of today's street network, enabling turn-by-turn route guidance on a high percentage of European, U.S. and Canadian roads as well as specific countries in Asia-Pacific.
Tele Atlas' compatibility with major navigation systems and its open system design have placed the company's technology at the heart of both consumer and business-to-business applications worldwide. From logistics to marketing to traffic and fleet management, in almost every sector of today's business and consumer world, Tele Atlas has built a reputation as an acknowledged pioneer and leader in the digital map industry. For more information, please visit www.teleatlas.com.
Arnout Desmet
Director - Asia-Pacific, Middle-East & Africa - New Markets
Moutstraat 132
B-9000 Gent
BELGIUM
Tel.: +32 9 244 88 97, Fax.: +32 9 222 74 12
Email: arnout.desmet@teleatlas.com
Introduction
Mobile mapping is a cutting edge technology applied by Tele Atlas to meet the challenge of gathering constantly changing road data rapidly and precisely. Vehicles equipped with digital cameras, installed in stereoscopic pair(s), as well as additional sensors for highly accurate positioning, capture real-world by driving the extensive road network in Europe.
The content-rich information that is gathered by the mobile mapping vans is sent to the Tele Atlas production centre, where over 500 digital cartographers use it to update and enrich the Tele Atlas databases. As the information can be gathered far more rapidly this way than by traditional survey methods, the databases are updated more frequently, thus providing customers with a more accurate database that is also more detailed.
Tele Atlas first tested this approach in the 1980s. The subsequent development of digital imaging technology, accurate GPS systems, inertial measurement unit positioning and digital mass storage have enabled it to become much more effective and turn mobile mapping in a practical reality that is now changing the world of digital mapping. As part of its programme to maintain outstanding quality, Tele Atlas has invested in more than 20 mobile mapping vehicles for its operations in Europe and in training a dedicated development and production team at the Tele Atlas production centre in India.
The accuracy and up-to-datedness of mobile mapping is contributing significantly to the effectiveness of advanced applications such as Advanced Driver Assistance Systems (ADAS ) and 3-D mapping.
Basic definition & description
The term mobile mapping in general is used as the technology to map and verify map data in the field. In this case, the definition of mobile mapping is used in a more strict sense as follows: Mobile mapping represents a heterogeneous type of sensor integration consisting of navigation sensors as well as imaging sensors, together time synchronized and mounted on a common platform (Schwarz & El-Sheimy, 1996).
Description of the mobile mapping system
The mobile mapping system (MMS) used within Tele Atlas has the digital cameras mounted on a vehicle (van). At least two of the digital cameras are installed in stereoscopic pair, spaced apart so that the combined image can provide 3-dimensional information. The capturing speed of the images is linked to the speed of the vehicle up to 3 images per second to obtain a complete recording of the information along the road network.
Figure 1: Mobile Mapping van
The picture resolution which is used per camera is typically 1200 * 960. Although higher resolution cameras can be mounted, this resolution was experienced as a good balance between data-storage requirements and features and attributes to be recognized.
The camera configuration used is typically between 4-6 (2 forward, 2 right side, 1 back-ward and 1 left side looking camera), depending on the roads types to be surveyed.
Figure 2: Various camera configurations - Mobile Mapping van
With these configurations, >95% of the visual components of the required objects/features can be recognized. Specifically for house-numbers and street name signs, the accuracy is lower and specific camera mounting is needed per country and per situation.
The positioning devices calculate the co-ordinates of a specific point on the vehicle. Following positioning sensors are included:
- 5Hz differential GPS unit
- 100Hz single axis gyro
- Odometer with rear wheel instrumentation
To handle the high incoming data stream, 1-4 PC's (one PC is linked to 2 cameras) are mounted in the back of the van, including UPS back-up facilities.
Figure 3: Front & rear view of the MMS equipment mounted in the mobile mapping van
The back-end of the mobile mapping system is an in-house processing unit that allows the visualisation of the imagery. It also allows photogrammetric measurements of objects on the images and the linking of the images and measurements to map data.
The Tele Atlas Mobile Mapping System (MMS) consists of two main components:
- MMS vehicle software & hardware to capture MMS data in the field;
- Post-process (PP) tools to handle & interpret MMS data (including vehicle position calculation).
- Quality verification: tools that are used either in the vehicle or just after data arrival in the production offices, to determine integrity and quality of the session files and eliminate any issues before the data goes to production;
- Data streaming & converting: tools that are used to extract session positional information or convert images to different file format;
- Data interpretation & database operation software: This is carried out by a combination of licensed and proprietary Tele Atlas software.
Description of the mobile mapping process
The MMS vehicle is used in field to gather
- a sequence of images (taken by cameras situated on different vehicle sides),
- positional information and
- calibration parameters.
Because of the high reliability and data stream demand, the MMS vehicle is only used for basic data streaming and data interpretation of positional information & camera frames. More sophisticated algorithms are handled in post-processing tools.
This approach gives the following advantages:
- The MMS vehicle can capture data at high frequencies. No data is lost in the capturing phase.
- If any error is detected in data interpretation and processing algorithms, the problem can be solved without a single need to redrive the area of interest (which gives a significant cost & time reduction).
What do we capture on basis of mobile mapping?
The databases created and maintained by Tele Atlas are used for route calculation, route guidance, turn-by-turn navigation and other geospatial applications. They contain particular map features and attributes.
There are five main categories of features and attributes:
- Addressing features, such as street names;
- Routing features such as importance and type of road, direction of traffic flow direction;
- Turn-by-turn information such as accurate road geometry and manoeuvre information;
- Visual interface features e.g. land cover and usage, for cartographic representation;
- Guidance features e.g. signposts, lane information, traffic signs.
The imagery materials collected by the MMS do provide to a large extent the necessary reference material to create and/or maintain the features and attributes referred to above as illustrated in some example imagery in figure 4 below.
Figure 4: Examples of high quality images collected by means of Mobile Mapping
Advantages of mobile mapping
The speed of capturing the imagery is the average driving speed on the roads and is not a function of the complexity to be mapped or verified. It is only a function of the traffic and the speed-limits. These driving speeds are therefore not limited to the interpretation-speed of a cartographer (since this is done in a post process). The frequency of verification of the real world can be up to 7 times higher versus traditional field verification methods, substantially increasing up-to-dateness and shortening the time-to-market.
A second major advantage of the mobile mapping process is that the system records the real world situation before the interpretation is done (from several angles). The approach overcomes the naturally limited performance of a human surveyor by shifting specific data collection and inspection activities to the office environment where human and computer resources can be optimally applied. Since we store reality in our imagery archive instead of recorded change detection of that reality, the real-world situation can be traced back and verified before an interpretation is done. This is a major advantage for the verification of the quality of the captured information, but it is also very useful to verify defect reports provided by customers.
One of the key benefits is that the data interpretation and the data processing are combined in one location, and executed with resources independent from the data collection activities. While the combination of data interpretation and data processing allows better quality, further improvements are realised by doing this interpretation of reality in-office and not under the strain of real traffic and the limited circumstances of the vehicle. Owing to the high speed capturing, benefits on product level can only be reaped when sufficient processing resources are at hand. Our large-scale production facilities offer us this advantage.
Because the position and orientation log of the MMS can be combined with the visual interpretation of lanes on the images, the system allows an accurate positioning and verification of road centrelines better than 1m positional accuracy (1s) and 2m (2s) (95% of all positional measurements have maximum deviation of 2m). The positional accuracy is also illustrated in the figure below comparing MMS logs with high-resolution georeferenced imagery.
Figure 5: MMS positional accuracy versus high resolution imagery
A major advantage of the mobile mapping process is that the captured high resolution ground images provide a geo-referenced source of new content which can be extracted in the production units at the required moment. The source is accurate, independent of interpretations and quality
Further information about Tele Atlas
Founded in 1984, Tele Atlas is a worldwide leading provider of digital maps and dynamic location content for a variety of navigation, location-based services and geospatial products and database solutions. Tele Atlas' database is a highly accurate reproduction of today's street network, enabling turn-by-turn route guidance on a high percentage of European, U.S. and Canadian roads as well as specific countries in Asia-Pacific.
Tele Atlas' compatibility with major navigation systems and its open system design have placed the company's technology at the heart of both consumer and business-to-business applications worldwide. From logistics to marketing to traffic and fleet management, in almost every sector of today's business and consumer world, Tele Atlas has built a reputation as an acknowledged pioneer and leader in the digital map industry. For more information, please visit www.teleatlas.com.