2012 Coastal Virginia NAIP Digital Ortho Photo Imagery

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Digital Georectified Image. | Source Geospatial Form: remote-sensing image | Type of Source Media: UnKnown

Flight planning was performed in IGIPlan from IGI over a

buffered boundary covering DOQQ extents provided by the USDA.

A 500m reduced resolution NED DEM file was used to determine

ground heights. A targeted flight altitude of approximately

30,000 feet above ground level was used. A minimum forward

overlap of 60+ACU- and minimum side overlap of 30+ACU- were used.

No ground elevation in the project area resulted in source

pixel dimensions greater than 1.05m or less than 0.5m. Cessna

Conquest aircraft were used for acquisition. Multiple

Intergraph Digital Mapping Camera (DMC) systems where utilized

in the data capture. The DMC is a digital frame camera that

produces a central perspective image with a nominal

focal length of 120mm projecting an image on a virtual CCD

measuring 13,824 by 7,680 pixels. The pixels are 12um by 12um.

Images from four panchromatic cameras modules, each with a

120mm lens projecting an image on a 7,168 by 4,096 CCD,

are assembled to create the virtual frame. Images captured

simultaneously from four 3,072 by 2,048 pixel multispectral

(MS) cameras with 30mm lenses produce red, green, blue and

near infrared images. These MS images are matched to the Pan

virtual image using the Post Processing Software from

Intergraph. All DMC systems used for capture have been

calibrated by the manufacturer. The calibration includes

measuring the radiometric and geometric properties of each

camera. These data are used in the Post Processing Software

to eliminate the radiometric and geometric distortion. The raw

captured pixel resolution of the panchromatic virtual frame

ranges from 0.60m to 1.04m across the project area depending

on terrain height. Each pixel is assigned a 12 bit digital

number (DN) by the analog to digital conversion performed after

each exposure. Each pixel is resampled during

orthorectification to an output resolution of 1m at a bit depth

of 8 for each image band. Four bands of data were captured for

each image+ADs- Blue: 400-580 nm, Green: 500-650nm, Red: 590-675nm

and Near infrared: 675-850 nm. The final product may only

include the RGB data. All aerial imagery was collected with

associated GPS data. When possible most imagery will also

include IMU data collection. GPS/IMU data were captured with

either an Applanix POS 510 system or IGI AEROControl. The

GPS data was utilized to control the aerial triangulation

process. All imagery was processed through an aerial

triangulation in which the airborne GPS data was constrained to

expected limits. Analysis was performed to assure that all

image frames fit within a strip and between strips by

evaluating the image and airborne GPS residuals. The final

adjustments assure a high quality relative adjustment and a

high quality absolute adjustment limited to the airborne GPS

data accuracy. This process assures the final absolute accuracy

of all geopositioned imagery. Both signalized and photo

identified ground control were used to QC and control the

IMU/GPS based aerial triangulation bundle block solution.

For each project area the latest NED was downloaded from the

USGS National Map Seamless Server website in late Spring

2012. Thirty Meter NED was used in all cases, and preferred

over the available ten meter spacing to minimize image smearing

and distortions that are exacerbated by a finer, but not more

accurate DEM. A visual inspection of the NED using color cycled

classification by elevation and a shaded relief was performed

to check for gaps, corruption and gross errors. When available

the NED was compared to known higher quality elevation sources

to detect flaws. Between 20-60 construction points per frame

derived from conjugant image measurements performed during

aerial triangulation were projected to the NED. The predicted

horizontal error for each point was added as an attribute in

the SURDEX enterprise database. An operator reviews ortho seams

in areas these predicted errors indicate horizontal error in

excess of the contract spe