In 2015, the North Central Texas Council of Governments facilitated the cooperative purchase of 4-band, 3-inch and 6-inch resolution digital aerial photography (orthos) for over 7500 square miles of the NCTCOG region including all of Collin, Dallas, Denton, Tarrant and Rockwall counties and portions of Hunt, Kaufman, Ellis, Johnson, Hood, Navarro, Parker, Palo Pinto and Wise counties. The orthos were collected in January and February 2015 (leaf-off) and are available for purchase via www.dfwmaps.com according to the following price schedule.
3-inch Digital Orthophotography
$36.00 per ortho tile [$167.27 per square mile]
6-inch Digital Orthophotography
$24.00 per ortho tile [$111.51 per square mile]
1-foot Digital Orthophotography
$12.00 per ortho tile [$55.76 per square mile]
2-foot Digital Orthophotography
$6.00 per ortho tile [$27.88 per square mile]
4-foot Digital Orthophotography
$3.00 per ortho tile [$13.94 per square mile]
8-foot Digital Orthophotography
$2.00 per ortho tile [$9.29 per square mile]
All images are georeferenced TIFF files and are sold as whole tiles only; price per square mile is provided only as a reference. Each TIFF ortho tile is 3,000' x 2,000', or 0.215 square miles. Sample images and a shapefile of the tile structure may be downloaded below; all orders for 2015 orthophotography products can be placed via www.dfwmaps.com. Before placing an order, read the frequently asked questions.
The specifications have been provided by the contractor for this project, Woolpert.
The coverage area for 2015 includes Dallas, Fort Worth, and surrounding urban and rural counties totaling 7,523 square miles, of which 448 square miles is 3” resolution. Four areas of 6” true orthoimagery were produced over the central business districts of Dallas and Fort Worth, as well as the IH-635/I-75 intersection and the Dallas North Tollway corridor from I-635 to Keller Springs Parkway, totaling approximately 24 square miles. The flight design achieved a nominal ground-pixel resolution sufficient for developing 3” and 6" pixel orthophotography without oversampling. It was also designed with sufficient forward overlap and strip side laps to ensure total project area coverage.
Camera
Microsoft UltraCAM Eagle
Altitude of Capture
9,900 feet AGL
Focal Length
100 mm in non-restricted airspace and 210 mm in restricted airspace
Capture Period
January 15 - February 8, 2015
Ground Conditions
Leaf off; free from snow, haze, fog, or dust; streams within normal banks
Atmospheric Moisture
Less than 5% cloud cover
Sun Angle
Greater than 30%
Forward Overlap
60%
Sidelap
30%
Coordinate System
Texas State Plane, North Central Zone
Horizontal Datum
NAD 83
Vertical Datum
NAVD 88
Units
US Survey Feet
Format
TIFF, MrSID Generations 2 and 4
Camera
Microsoft UltraCAM Eagle
Altitude of Capture
9,500 feet AGL
Focal Length
100 mm
Capture Period
January 15 - February 8, 2015
Ground Conditions
Leaf off; free from snow, haze, fog, or dust; streams within normal banks
Atmospheric Moisture
Less than 5% cloud cover
Sun Angle
Greater than 30%
Forward Overlap
60% (80% for True Ortho areas)
Sidelap
30% (60% for True Ortho areas)
Coordinate System
Texas State Plane, North Central Zone
Horizontal Datum
NAD 83
Vertical Datum
NAVD 88
Units
US Survey Feet
Format
TIFF, MrSID Generations 2 and 4
Control was established using Dallas and Fort Worth Virtual Reference Stations (VRS). Aerotriangulation was performed using industry-accepted procedures on an approved softcopy workstation to support the horizontal accuracy requirements of the digital orthophotography. The RMS of known ground points meets or exceeds 1.0 ft. in x, y, or z.
The imagery was produced using best available DEM data, including ACS data provided by NCTCOG and LiDAR/DEM data from the Texas Natural Resource Information System (TNRIS). The orthoimagery was colorbalanced and to radiometric parameters established during the pilot phase of the project. The most nadir part of every image was used in the mosaicking. Mosaic seam lines are created to ensure that joins do not cut hard detail where avoidable. Mosaic lines do not cross through above-ground structures unless unavoidable. Seams through or along streets are placed to avoid obscuring or artificially creating centerlines, curbs, and sidewalks. Quality control steps were performed during production of the orthoimagery to ensure the orthoimagery is inspected for compliance with required aesthetic and spatial criteria.
Woolpert produced 4-band digital orthoimagery with a 0.25 pixel resolution for the defined 448 square mile project area and a 0.5-foot pixel resolution for the defined 7,075 square mile project area. The images were interactively mosaicked to produce imagery with consistent tone, density, and color balance. The project-wide imagery was delivered in TIFF format with accompanying world files. Full tiles were used for the entire project area; Woolpert used NCTCOG’s provided 2,000’ X 3,000’ tile grid for the 2015 project.
The final orthoimagery meets the American Society of Photogrammetry and Remote Sensing (ASPRS) Class I standard for 1” = 50 and 1"=100' scale mapping. NCTCOG's review team inspected the orthoimagery using Woolpert’s SmartView Connect web-based quality assurance system, which allows reviewers to immediately communicate issues found in the imagery through placement of attributed polygons. Any non-conforming orthoimagery was corrected and posted to the application for approval by the review team. Upon approval by NCTCOG, the final orthoimagery was delivered tiled to the NCTCOG grid (2,000' x 3,000' tiles), in 4-band (RGB+NIR) TIFF format and 3-band (RGB) MrSID compressed format (Generation 2 , 18:1 compression ratio) and 4-band (RGB+NIR) TIFF format and 4-band (RGB) MrSID compressed format (Generation 4 , 18:1 compression ratio).
North Central Texas Council of Governments | 616 Six Flags Drive P.O. Box 5888 Arlington, TX 76005-5888
Main Operator: (817) 640-3300 | Fax: (817) 640-7806
