USDA NAIP 2007 Orthoimagery
Projection: UTM NAD83
Resolution: 1 or 2 Meter
This data set contains imagery from the National Agriculture
Imagery Program (NAIP). NAIP acquires digital ortho imagery
during the agricultural growing seasons in the continental U.S..
A primary goal of the NAIP program is to enable availability of
ortho imagery within one year of acquisition. NAIP provides four
main products: 1 meter ground sample distance (GSD) ortho
imagery rectified to a horizontal accuracy of within +/- 5
meters of reference digital ortho quarter quads (DOQQ's) from
the National Digital Ortho Program (NDOP); 2 meter GSD
ortho imagery rectified to within +/- 10 meters of reference
DOQQs; 1 meter GSD ortho imagery rectified to within +/- 6
meters to true ground; and, 2 meter GSD ortho imagery rectified
to within +/- 10 meters to true ground. The tiling format of NAIP
imagery is based on a 3.75' x 3.75' quarter quadrangle with a 300
meter buffer on all four sides. NAIP quarter quads are formatted
to the UTM coordinate system using NAD83. NAIP imagery may
contain as much as 10% cloud cover per tile. This file was
generated by compressing NAIP quarter quadrangle tiles that
cover a county. MrSID compression, with mosaic option, was
used. Target values for the compression ratio are (15:1)
and maximum number of compression levels are used.
NAIP imagery is available for distribution within 60 days
of the end of a flying season and is intended to provide current
information of agricultural conditions in support of USDA farm
programs. For USDA Farm Service Agency, the 1 meter GSD product
provides an ortho image base for Common Land Unit boundaries and
other data sets. The 1 meter NAIP imagery is generally acquired
in projects covering full states in cooperation with state
government and other federal agencies who use the imagery for a
variety of purposes including land use planning and natural
resource assessment. With an annual cycle, NAIP is also used for
disaster response often providing the most current pre-event
imagery. While suitable for a variety of uses the 2 meter
GSD NAIP imagery is primarily intended to assess crop condition
and compliance to USDA farm program conditions. The 2
meter imagery is generally acquired only for agricultural areas
within state projects.
Color Digital imagery was collected with a Leica ADS40 Digital Sensor.
The ADS40 CCD array includes 12,000 pixels across track at 6.5 microns.
The digital imagery was acquired with a minimum of 20% sidelap, then
processed using Leica software to produce geo-referenced raster swaths.
The ADS imagery is subsequently used in the Aerial Triangulation (AT)
process in preparation for orthorectification. The horizontal accuracy
of the orthorectified imagery is primarily determined by the quality of
the airborne GPS, Inertial Measurement Unit (IMU) data and the surface
model (digital elevation model or DEM). The AT process is initiated with
the population of ADS project files with ABGPS/IMU data, horizontal
control from USDA furnished mosaicked DOQQs (mDOQQs) and vertical
control picked from the USGS DTED2 DEM data. IMU rotational data is
checked by reading common points on the mosaicked DOQQs and on the
new imagery. As a final check, stereo models are analyzed for parallax.
The absolute orientations for each swath containing exterior orientation
parameters for scan line is then output for use in orthorectification.
Each DOQQ is inspected for relative horizontal accuracy with adjacent DOQQ
tiles. Each DOQQ is inspected for image quality. DOQQs are color and
radiometrically balanced over a block consisting of a large number
of images. A sample of DOQQs is selected and inspected for relative
horizontal accuracy with the USDA furnished mDOQQs. Completed and
approved DOQQs are assembled into a countywide MrSID file, using a
compression factor of 1:15.