Mid-Region Council of Governments (MRCOG) coordinated digital acquisition of six inch natural color digital orthophotography for an area in Bernalillo County, Sandoval County, Valencia County, and Soccoro County New Mexico of approximately 1930 square miles.
The purpose of this Project was to consolidate contiguous areas of interest for acquiring digital orthophotography data, for realizing a cost savings in data acquisition and production costs, and for sharing any data produced under this Project among the cooperating parties.
The bounding coordinates provided within the Spatial Domain section represent a rectangle in which the project is located. Data produced in this project area include orthophotography tiles base upon a modified Public Land Survey System (PLSS) tiling scheme. The actual project boundary is delimited by full PLSS sections which fall within the boundaries of 60 7.5' USGS quadrangles (Alameda, Albuquerque East, Albuquerque West, Arroyo de las Calabacillas, Belen, Benavidez Ranch, Bernalillo, Bernalillo NW, Bosque Peak, Canada, Capilla Peak, Casa Colorado, Cerro Conejo, Chilili, Cochiti Dam, Collier Draw, Dalies, Dalies NW, Edgewood, Escabosa, Golden, Hagan, Hubbell Spring, Isleta, La Joya, La Joya NW, La Mesita Negra, La Mesita Negra SE, , Lemitar, Loma Machete, Los Griegos, Los Lunas, Los Lunas SE, Madrid, Manzano Peak, Mesa Del Yeso, Milbourn Ranch, Mount Washington, Placitas, San Acacia, San Felipe Mesa, San Felipe Pueblo, San Felipe Pueblo NE, San Pedro, Sandia Crest, Sandia Park, Santa Ana Pueblo, Santo Domingo Pueblo, Santo Domingo Pueblo SW, Sedillo, Tajique, Tetilla Peak, The Volcanoes, Tijeras, Tome, Tome NE, Tome SE, Veguita, Wind Mesa). Project tasks included: 1) Digital Aerial Photography and Control, 2) Aerial Triangulation (AT), 3) Digital Elevation Models preparation using existing Bernalillo County 1999 LiDAR, Sandoval County 2003 digital surface model, MRCOG 2004 correlated surfaces, and newly developed correlated surfaces to support orthorectification, and 4) Digital Orthorectification. The 8025 final deliverable 0.5' resolution digital orthophotography tiles are approximately 2640' x 2640' square. Deliverables include: - 24-Bit Natural Color 0.5' resolution digital orthophotography tiles in Uncompressed TIFF format with associated World Coordinate File - 24-Bit Natural Color 0.5' resolution digital orthophotography tiles in ECW compressed format - Digital Natural Color aerial photography were acquired using an Intergraph Z/I Imaging DMC® (Digital Mapping Camera)-Serial # - DMC18. The flight design achieved a nominal ground pixel resolution sufficient for developing 6" pixel orthophotography without oversampling. It was also designed with sufficient forward overlap and strip side laps to ensure total project area coverage according to the following flight specifications: Altitude: 4500' above mean terrain Focal Length: 120 mm (4.72") Imagery Scale: 1 "=950', (Photo Scale PS: 1:11,400) Conditions: Leaf Off, Cloud Free, Optimum Sun Angle Forward Overlap: 60% Sidelap: 30% In addition to airborne Global Positioning System (GPS) control and Inertial Measurement Unit (IMU) data, ground control were acquired under the supervision of a registered surveyor at sufficient density and accuracy to support production of digital orthophotography to the specifications required. Control was collected in New Mexico State Plane, Central Zone, North American Datum (NAD) 83, North American Verticle Datum (NAVD) 88, Horizontal Accuracy Reference Network (HARN), U.S. Survey Feet. Aerotriangulation was performed using industry-accepted procedures on approved softcopy workstation to support the horizontal accuracy requirements of the digital orthophotography-Root Mean Square Error (RMSE) of known ground points does not exceed 1 foot in x, y, or z. Digital Elevation Models (DEMs) were constructed using industry-accepted procedures with sufficient density of points to support production of digital orthophotography according to the required specifications. Digital orthophotography was created using industry accepted procedures. The most nadir part of every image was used during Digital Orthorectification. Mosaic seam lines were 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 were placed to avoid obscuring or artificially creating centerlines, curbs, and sidewalks.
809 Copper Ave. NW
Bohannan Huston Inc.
All mosaicked digital orthophoto tiles were inspected in regard to: Positional accuracy, Surface accuracy, and Radiometric quality.
Compliance with the accuracy standard was ensured by the placement of photo identifiable ground control points and the collection of airborne GPS and IMU data.
Meets National Map Accuracy Standards at 1" = 200' (1 :2,400); Meets American Society of Remote Sensing and Photogrammetry (ASPRS) Class 1 Standards for Large-Scale Maps (horizontal); All ground control adhered to the "Geometric Geodetic Accuracy Standards and Specifications for Using Relative Positioning Techniques", FGDC Version 5.0, of August 1, 1989, published by the Federal Geodetic Control Subcommittee (FGCS)
A combined XY RMS value was calculated based on the imagery utilized in the east AT block. This value represents an estimate of the accuracy of the horizontal control coordinate measurements expressed in feet.
A combined XY RMS value was calculated based on the imagery utilized in the Albuquerque metro area. This value represents an estimate of the accuracy of the horizontal control coordinate measurements expressed in feet.
The digital imagery mission was composed of a total of 78 flight lines.
Bohannan Huston Inc. established ground control to support the aerotriangulation process. A total of 66 surveyed points were paneled to support the AT process.
Bernalillo County 1999 LiDAR derived digital terrain model LiDAR surface data were provided by MRCOG to support the production process by providing ground elevations for the orthorectification process. Sandoval County 2003 DEMs were provided by MRCOG. Various autocorrelated areas from the MRCOG 2004 project and newly (2006 flight) autocorrelated elevation models were incorporated as needed.
DMC data and accompanying GPS and IMU data were downloaded from hard disks and checked to verify that no files were corrupted and that all data could be downloaded. Digital aerial imagery that was used for this project included three-band (Red, Green, and Blue) images. The 12-bit image frames were inspected in an uncorrected state to verify the integrity of each flight line. Side lap issues were found in the eastern portions of Bernalillo County and Sandoval County. This made necessary a reflight mission to correct this problem.
Aerotriangulation for the project was accomplished using multiple AT blocks where the horizontal and vertical positions of all ground control points in each block were observed on the 12-bit imagery. Ground control, GPS and IMU information were ingested and tie points between flight lines were identified. ISAT produced the bundle adjustment. The results of the adjustment were verified for nominal accuracies to within 1 US Survey Foot. An ASPRS certified photogrammetrist inspected the aerotriangulation process for quality.
The various digital elevation models supplied and created were used to create orthorectified tiles. The data were inventoried and ingested into a PostgreSQL database which is integrated into the workflow for the differential rectification of the digital orthophotography.
Consistent project lookup tables (LUTs) for the 12-bit data were created using a gamma function and applied to each frame of photography. LUT applied frame data were then resampled from 12-bit to 8-bit format prior to orthorectification.
Each frame of digital imagery was differentially rectified to produce 8-bit digital orthophotos in natural color at a resolution of 0.5' per pixel. Orthophotos were inspected for accuracy related to radiometric quality.
Master color balancing was conducted across large areas of the project to create consistent tonal and color balance among adjacent image frames yielding a uniform overall appearance. Using master color balancing metadata, several mosaic blocks were submitted to the mosaicking and tiling process. Final 24-bit natural color tiled output was inspected for data voids and radiometric integrity.
The completed digital orthophoto tiles were checked for image quality. Quality control included assessment of every final tile in regard to positional accuracy, surface accuracy, and radiometric quality. Tiles were inspected against seam line placement to ensure that no hard detail was cut. Minor artifacts and adjustments were corrected using Adobe Photoshop in an interactive editing session.
Deliverable tiles were clipped and named according to output delivery requirements and packaged on portable hard drives.
Project level metadata describing the orthophoto production process was developed in xml format.
Any resale of this data is strictly prohibited without written authorization of the cooperating parties.
7500 Jefferson St. NE