Process_Description:
DOQQ Production Process Description;
USDA FSA APFO NAIP Program 2019;
The imagery was collected using the following digital sensors:
Leica ADS-100 (Serial Number 10530),
Leica ADS-100 (Serial Number 10510),
Leica ADS-100 (Serial Number 10515),
Leica ADS-100 (Serial Number 10522),
Leica ADS-100 (Serial Number 10552)
with Flight and Sensor Control Management
System (FCMS) firmware:
v4.57,
Cameras are calibrated radiometrically and geometrically
by the manufacturer and are all certified by the USGS.
Collection was performed using a combination of the
following twin-engine aircraft with turbines flying
at 27,100 ft above mean terrain.
Plane types:
C441, C414
Tail numbers:
N441EH,
N414EH,
N440EH,
N441FS,
N2NQ,
With these flying heights, there is a 27% sidelap,
giving the collected data nominal ground sampling distance
of 0.60 meters.
Based-upon the CCD Array configuration present in
the ADS digital sensor, imagery for each flight
line is 20,000-pixels in width. Red, Green, Blue,
Near-Infrared and Panchromatic image bands were collected.
The ADS 100 has the following band specifications:
Red 619-651,
Green 525-585,
Blue 435-495,
Near Infrared 808-882,
all values are in nanometers.
Flight planning was performed in Leica MissionPro over a
buffered boundary covering DOQQ extents provided by the USDA.
A 500m reduced resolution DEM file was used to determine
ground heights. A targeted flight altitude of approximately
27,000 feet above ground level for native 60cm image
acquisition with sidelap of 27% was used
for flight planning parameters. Four Cessna Conquests were utilized
for acquisition, the seamline
shapefile clarifies which aircraft were used for a given area.
All aircraft were equipped with Leica
ADS100 systems where utilized for data
capture. The Leica ADS100 pushbroom sensor
has been calibrated by the manufacturer as well as validated
against a local calibration range. The calibration includes
measuring the radiometric and geometric properties of the
camera. These data are used in the Post Processing Software
to eliminate the radiometric and geometric distortion.
All aerial imagery was collected with associated GPS/IMU
data. ADS collection requires high quality IMU data for
processing and was critical for early access hosting of digital
data to the web for USDA interim access and review.
After early access web delivery was complete, all
imagery was triangulated using Leica XPro in which
the airborne GPS data was constrained to expected limits.
To validate the accuracy of the block adjustment derived from
GPS/IMU, sensor parameters and conjugate point measurements,
photo identifiable ground control points were field surveyed within
each State. These points were surveyed using GPS techniques to
produce coordinates that are accurate to +/- 0.25 meters RMSE in XYZ.
The GPS surveying techniques utilized assured that the coordinates
are derived in the required project datum and relative to an approved
National Reference System. If the block does not fit the
control points within specifications the pass and tie
points were reviewed for blunders and weak areas. If,
after these corrections were made, the block still
does not fit the control well the GPS and IMU processing were
reviewed. Once the block has proper statistics and fits the
control to specifications, the final bundle adjustment was
made. As AT points are frequently on man-made and other
vertical features not included in the DEM, these ortho
points can only be used to indicate regions of error by the
clusters of points that predict excessive horizontal displacement.
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. Surdex Grouping Tool provides real-time updates
of the USDA APFO Image Metrics. The image technician adjusts
image correction parameters to bring the radiometric
characteristics of large groups of images within the Image
Metrics ranges. For each project area the highest resolution
DEM or LiDAR was obtained and utilized for rectification of captured
imagery.
A visual inspection of the final DEM using color cycled
classification by elevation and a shaded relief was performed
to check for gaps, corruption and gross errors.
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 specifications. Any imagery errors
introduced by source DEM required patching from an alternate
perspective or strip of photography.
Processing hardware used included various brands of survey grade
GPS receivers, various brands and models of computers,
RAID6 storage, calibrated monitors, various brands of monitor
calibration colorimeters. Leica XPro was used for post
processing of ADS pushbroom data, triangulation and
orthorectification. SURDEX software was used to color correct
and remove bidirectional reflectance, vignetting and other
illumination trends. USDA APFO Image Metrics are measured and
images corrected to conform to the Image Metrics using
SURDEX software. GPS/IMU data was reduced to projected
coordinates in the appropriate UTM zone using
Inertial Explorer software from Novatel. Aerial Triangulation
and orthorectification was performed using Leica XPro. SURDEX
software was used to adjust for minor radiometric
variation between adjacent images. SURDEX software was used
to calculate the optimal seam path, check seam topology and
create master tiles. SURDEX ortho software generates
occlusion/smear polygons used during seam review
of steep terrain. SURDEX software was used to
visually inspect master tiles for seam and image defects.
SURDEX software was used to project and cut final DOQQ image
files from masters. SURDEX software was used to create CCM
metadata. Lizardtech GeoExpress version 10.0.0.511 was used
to create the CCM image file. SURDEX software was
used to perform final formatting, QC and naming of the DOQQ.
USGS metadata parser software was used to validate the metadata.
Various versions of Microsoft Windows were used in all phases of
production. Grouping Tool was used again after DOQQ and CCM
production to provide a quality assurance check. Individual
DOQQ and CCM may not meet the USDA APFO Image Metrics ranges
due to land cover. The goal is to have the state as a
whole meet the Image Metrics. All products are reviewed
by independent personnel prior to delivery.
The delivery is checked for omissions, commissions,
naming, formatting, specification compliance and data integrity.