Bohannan Huston Completes Massive Photogrammetric Mapping Project

ALBUQUERQUE, NM /PRNewswire/ -- Aerial mapping for the largest photogrammetric mapping project in the U.S. was completed nearly two weeks ahead of schedule by Bohannan Huston Inc. (BHI), thanks to comprehensive planning and continuous communication. The acquisition spans 17 adjacent counties of the Dallas/Fort Worth area, covering 13,715 square miles of north central Texas, and requiring the synchronization of three aircraft flying Intergraph Digital Mapping Cameras (DMC).

This project required more than 59,000 individual frames to be processed for the client, the Dallas District of the Texas Department of Transportation (TxDOT). BHI provided 0.5' natural color digital orthophotography and a corresponding two-foot digital surface model for the complete 17-county area, including the Dallas-Ft. Worth metroplex. Over 10 terabytes of digital deliverables were produced for this project, which extended across the North Central Texas Council of Governments (NCTCOG) region.

"The narrow January-March acquisition window was tightened further by the need to operate in the busy airspace above Dallas-Fort Worth Airport and Love Field," said Dennis Sandin, Senior Vice President of BHI. "To meet TxDOT's schedule, all flight lines had to be planned and approved months in advance." BHI used three DMC sensors for acquisition, cluster computing to process the imagery, and a refined auto triangulation technique to provide the surface. The auto triangulation technique is a proprietary approach perfected by BHI for the DMC camera.

In addition to serving as a blueprint for large-area photogrammetric mapping projects, the Dallas-Fort Worth endeavor is a study in intergovernmental cooperation. The natural color orthophotos, contour maps, and digital elevation maps generated will ultimately be accessed by 17 counties, hundreds of cities, and numerous government agencies at all levels, including FEMA and TxDOT, collectively represented by the NCTCOG.

Through interagency cooperation, NCTCOG is able to obtain photogrammetric mapping with a frequency and at a level of detail that many participants could not afford on their own. The consortium has established a two-year update cycle for its base mapping of 6-inch pixel resolution in the orthophotos.

"Our biggest goal is saving the taxpayer money," said Mark Eder, District Survey Coordinator for TxDOT, which assumed the leadership role in this year's mapping. "The price of this project is minimal compared with the cost savings."

Within TxDOT, the orthophotos and elevation maps will be used to preplan and design transportation projects, from road striping and paving to highway widening and construction. By comparing the 2007 images with the ones from 2005, the state can identify growth patterns and expand the transportation network accordingly.

As the project unfolded, TxDOT was able to view near-real-time progress on a special project Web site created for their use. The public Web site allowed all the stakeholders to see updates on the project's progress, techniques for acquisition and processing the data in record time, and quality assurance requirements to guarantee product delivery. Also included was an in-depth discussion of the auto correlation process, the accuracy expected and achieved, areas where the process worked well, and comparisons to existing LiDAR surfaces. Product delivery will be through a unique data distribution system developed for this project, which maximizes the return on the investment for the TxDOT engineering community.

About BHI
Bohannan Huston Inc. (BHI) provides engineering services, spatial data and mapping services, and advanced engineering technologies. BHI has been in business for more than 48 years and employs more than 250 staff in its Albuquerque, NM, headquarters and Denver, Las Cruces, and Dallas offices. In the spring of 2007, BHI with Surdex Corp. of Chesterfield, MO, formed a joint acquisition company. This represents a co-investment in sensor technology processed and software to aggressively address the accelerating movement from film photography capture to direct digital imagery and LiDAR data acquisition. Together, our two companies bring over a century of professional engineering, surveying, photogrammetric mapping, aerial acquisition, and GIS services to the marketplace. BHI has moved forward with the joint acquisition to ensure schedule, quality, and technological control of aerial sensed imagery for our clients. For more information contact Loretta Davis at 505-798-7850.

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