2016 Coastal Texas NAIP Digital Ortho Photo Imagery

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

Digital imagery was collected at a nominal GSD of 80cm

or 40cm using nine Cessna 441 aircraft flying at

an average flight height of 8400m AGL for 80cm acquistion

and 4400m AGL for 40cm acquisition. Aircraft flew with

Leica Geosystem's ADS100/SH100 digital sensors with

firmware 4.54 or ADS100/SH120 digital sensors with

firmware 4.54. Each sensor collected 12 image bands

Red,Green,Blue and Near-infrared at each of three

look angles; Backward 19 degrees, Forward 26 degrees

and Nadir for the SH100. Backward 10 degrees, Forward

14 degrees, and Nadir for the SH120. The Nadir Green

band was collected in high resolution mode effectively

doubling the resolution for that band. The ADS100

spectral ranges are; Red 619-651nm,Green 525-585nm, Blue

435-495nm and Near-infrared at 808-882nm. The CCD arrays

have a pixel size of 5.0 microns in a 20000x1 format at

nadir; a 18000x1 format at the backward look angle

and a 16000x1 format at the forward look angle.

The CCD's have a dynamic range of 72db and the A/D

converters have a resolution of 14bits. The ADS is

a push-broom sensor the ground footprint of the imagery

is approximately 8km wide at a nominal 40cm GSD and 16km

wide at a nominal 80cm GSD by the length flightline.

The maximum flightline length is limited to approximately

240km. The factory calibrations and IMU alignments for

each sensor (Serial Numbers: 10511,10512,10514,10522,

10527,10530,10531,10534,10540,10554,12502 ) were tested

and verified by in-situ test flights before the start

of the project. The Leica MissionPro Flight Planning

Software is used to develop the flight acquisition plans.

Flight acquisition sub blocks are designed first to

define the GNSS base station logistics, and to break

the project up into manageable acquisition units. The

flight acquisition sub blocks are designed based on

the specified acquisition season, native UTM zone of

the DOQQs, flight line length limitations (to ensure

sufficient performance of the IMU solution) as well

as air traffic restrictions in the area. Once the sub

blocks have been delineated they are brought into

MissionPro for flight line design. The design

parameters used in MissionPro will be 30% lateral

overlap and 40cm or 80cm resolution. The flight lines

have been designed with a north/south orientation.

The design takes into account the latitude of the

state, which affects line spacing due to convergence

as well as the terrain. SRTM elevation data is

used in the MissionPro design to ensure the 50cm

GSD is achieved over all types of terrain. The raw

data was downloaded from the sensors after each

flight using Leica XPro software. The imagery was

then georeferenced using the 200Hz GPS/INS data

creating an exterior orientation for each scan line

(x/y/z/o/p/k). Leica Xpro APM software was used to

automatically generate tiepoint measurements between

the foward, nadir and backward look angles for each line

and to tie all flight lines together. The resulting point

data and exterior orientation data were used to perform

a full bundle adjustment using ORIMA software. Blunders

were removed, and additional tie points measured in weak

areas to ensure a robust solution. Once the point data

was clean and point coverage was acceptable,

photo-identifiable GPS-surveyed ground control points

were introduced into the block adjustment. The bundle

adjustment process produces revised exterior orientation

data for the sensor with GPS/INS, datum, and sensor

calibration errors modeled and removed. Using the

revised exterior orientation from the bundle adjustment,

orthorectified image strips were created with Xpro

software and the June 2014 USGS 10m NED DEM. The Xpro

orthorectification software applies an atmospheric-BRDF

radiometric correction to the imagery. This correction

compensates for atmospheric absorption, solar

illumination angle and bi-directional reflectance. The

orthorectified strips were then overlaid with each other

and the ground control to check accuracy. Once the accuracy

of the orthorectified image strips were validated the

strips were then imported into Inpho's OrthoVista 7.0

package which was used for the final radiometric

balance, mosaic, and DOQQ sheet creation. The final

DOQQ sheets, with a 300m buffer and a ground pixel

resolution of 1m or 60cm were then combined and compressed

to create the county wide CCMs.