Workflow of Oblique Imagery

In 2005, Blom Aerofilms became the licensed franchise operator of Pictometry oblique aerial imaging technology in Europe. The planned image collection in 15 countries, however, was hampered by the inability to effectively track and manage the sheer volume of data through the workflow. The solution was an automated web-based spatial data management system (SDMS) that has improved workflow efficiency by nearly 30%.

The Blom Group saw tremendous potential in the oblique technology of Pictometry International of Rochester, NY, and to date the license covers 26 countries in western and central Europe. The licensing included the purchase of 15 camera systems including software for handling every phase from flight planning, data storage and retrieval to processing and delivery. Two processing facilities were established, one in England and one in Italy, and images were collected of hundreds of cities and towns; amounting to 3 million in one year alone. While some municipalities were being imaged on speculation, many commercial orders were received, including a major contract from Microsoft that created a tremendous demand for fast delivery of end products.

Oblique Imaging

The Pictometry oblique system includes a suite of five natural-colour aerial cameras: one points to nadir and four are off-nadir at 40° deflection angles. Each point on the ground is imaged from at least 12 perspectives during a single pass. The orthorectified images have a high photogrammetric accuracy. Oblique imagery is used extensively in applications where off-nadir views reveal features not typically visible in nadir views, including tax assessment, tactical law enforcement, property management and engineering. In Europe, oblique images have become popular among online Yellow Pages users, who enjoy street-level three-dimensional views of stores, hotels and tourist sites.

Manual Endeavours

Oblique image collection for so many countries constrains tracking and managing the sheer volume of data. At 10- to 15cm resolution, oblique images for one project take up many gigabytes. Other data and documents, such as flight line shapefiles, GPS and IMU points, and digital terrain models, also have to be stored and retrieved. At any point in the workflow, two terabytes of data may need to be accessed and served from five storage locations. Finding the images and the other data, matching them to a ground location and ensuring they arrive at the correct workstation at the right time were painstaking manual endeavours. Furthermore, oblique processing involves five desktop software applications and 27 discrete steps, nearly all of which require manual supervision. Managers spent much time determining where data files were in the workflow at a given time. In addition, making up-to-date status reports for clients forced managers to personally make inquiries with supervisors and technicians at the two processing facilities. Data tracking and reporting had thus become a hidden, but significant, drag on efficiency.

Tackling Size

Examination of commercial data-management software revealed that these are too narrowly focused on handling the data. Therefore, solutions were built around the concept of managing the entire workflow. The starting point was the Land Registry System (LRS), an off-the-shelf software package built earlier by International Land Systems Inc. (ILS) to automate registering, archiving, and awarding land titles and offering built-in spatial data handling functionality. LRS was designed for easy adaptation to nearly any land management workflow and this flexibility enabled the creation of the spatial data management system (SDMS) solution. The size of a single raw oblique image is around 32MB, which impedes processing because most software is designed to handle mosaiced files of that size and to process them in parts. However, a raw oblique scene has to be processed in whole and this was solved by modifying an enterprise-level, open-source content management application, Alfresco, to store the files and then use image server technology from LRS to move the files through the Pictometry environment.

Automation

SDMS automates and controls many of the operations in the five phases of the oblique workflow. In-house developed software is integrated with existing business processes to eliminate manual work as much as possible. For example, the software automatically populates fields in Pictometry query screens, which saves time and eliminates key-entry mistakes. Even when information has to be entered manually, it is used to automatically populate other fields and to make decisions about the next action. This keeps the processing stream moving from one step to another regardless of whether technicians are present. For example, the processing of telemetry data from the Applanix IMUs is labour-intensive because a human has to go through a long sequence of Yes/No mouse clicks on drop-down menus. With SDMS processing, going through the sequence has been reduced by 30%.

Tracking Data

SDMS also tracks the location and status of all data needed for product generation. Starting with the Flight Planning module, the system assigns each frame of the flight path to the appropriate GIS-based polygon on the ground. Next, all collected imagery, GPS points and IMU data sets are tagged to that polygon. As the raw data are delivered to one of the two processing facilities, SDMS keeps track of where each is stored, whether in the Oracle database or on a disk drive, and eliminates manually searching for a digital data file. If the software cannot access a data file directly, an e-mail message is automatically generated on what file is needed, where it is located and where it should be delivered. Tracking functionality also saves time for production managers by automatically creating daily spreadsheet reports (Figure 1). These reports provide updated details on where a given project is in the workflow and estimates when the product will be completed. The reports can be queried directly, allowing instant responses to queries from customers.

Web Access

In addition, access via the web is possible, improving transparency for clients who can log into SDMS via the internet and query the system themselves to monitor progress (Figure 2). Under an OEM agreement with ESRI, the system embeds ArcGIS Server so that clients or managers can view a map of Europe and click on an area of interest to retrieve progress statistics both spatially and in tabular form just by mouse clicking (Figure 3). Standard zoom and pan tools are available to navigate through the base map with the option to view images. External personnel can interact with the production as needed; for example, during aerial acquisition, pilots can log into SDMS from their handheld PDAs and enter notes to indicate changes or deviations made to the planned flight lines during the mission.

Significant Payoffs

The new SDMS solution is fully operational and the implementation is a success with significant payoffs. The next step will be to take enterprise access further to allow distributed processing. Soon, employees from several facilities across Europe will perform processing steps by remote access to one central location. This will see further efficiency increases in data handling and management.

Acknowledgements

Thanks are due to Nigel Edmead.