This data set contains imagery from the National Agriculture Imagery
Program (NAIP). These data are digital aerial photos of the entire state of
Montana, taken in the year 2011. The spatial resolution of the images is 1
meter.
The State Library provides the data through several
avenues:
- Online viewing as either natural-color or false-color
infrared images at
http://montana.maps.arcgis.com/home/webmap/viewer.html?webmap=437353b569ea46319fb657e1c122b3d1
- A 4-band (infrared, red, green, blue) map service at
https://gisservice.mt.gov/ArcGIS/rest/services/MSDI_Framework/NAIP_2011/ImageServer
- For download as natural-color compressed 24-kilometer tiles in MrSID format
at
http://mslapps.mt.gov/Geographic_Information/Data/Aerial_Photos/naip_2011_default.aspx.
These images are in Montana State Plane coordinates, NAD1983, units meters.
The state is covered by 2,732 images with a total size of 55
gigabytes.
- As 4-band GeoTIFF images. The state is covered by 6,022
images, each of about 370 megabytes. The images are in Montana State Plane
coordinates and each of covers an area slightly over 5 miles square. To order
GeoTIFF images from the State Library, select the quadrangles you want from
the tiff index shapefile at
ftp://ftp.geoinfo.msl.mt.gov/Data/Spatial/MSDI/Imagery/2011_NAIP/naip_2011_tif_index.zip
and send them to the Library, along with a storage device of sufficient size
to hold them and return postage for the device.
An ESRI shapefile index
showing the dates and times the images were acquired is available at
ftp://ftp.geoinfo.msl.mt.gov/Data/Spatial/MSDI/Imagery/2011_NAIP/24_km_tiles/00_NAIP_2011_Dates.zip.
Time period of content:
Beginning date: 07/15/2011
Ending date: 09/21/2011
Currentness reference: Ground
Condition
Access constraints: None
Use constraints:
The Montana State Library provides this product/service for informational
purposes only. The Library did not produce it for, nor is it suitable for
legal, engineering, or surveying purposes. Consumers of this information
should review or consult the primary data and information sources to ascertain
the viability of the information for their purposes. The Library provides
these data in good faith but does not represent or warrant its accuracy,
adequacy, or completeness. In no event shall the Library be liable for any
incorrect results or analysis; any direct, indirect, special, or consequential
damages to any party; or any lost profits arising out of or in connection with
the use or the inability to use the data or the services provided. The Library
makes these data and services available as a convenience to the public, and
for no other purpose. The Library reserves the right to change or revise
published data and/or services at any time.
Farm Services Agency Digital Orthophoto Specifications. The specified
accuracy for 1-meter imagery such as this is 5 meters.
Lineage:
Source information:
Originator: Aerial Photography Field
Office
Publication date: 2011
Title: Aerial Photography
Source scale denominator: 40000
Beginning date: 07/15/2011
Ending date: 09/21/2011
Process step:
Cessna Conquest aircraft were used for acquisition of the aerial images.
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
12 um. 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. The targeted flight altitude was approximately 30,000
feet above ground level. 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; Blue:
400-580 nm, Green: 500-650 nm, Red: 590-675 nm and Near infrared: 675-850
nm.
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 Spring2011. Thirty Meter NED was used in
all cases, and preferred over the available 10 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 higherquality 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 reviewed ortho seams in areas these
predicted errors indicated horizontal error in excess of the contract
specifications. Any imagery errors introduced by source NED required
patching from an alternate DEM or frame of photography with a different
perspective. Hardware used included the DMC, various brands of L1/L2 Survey
grade GPS receivers, various brands and models of computers, RAID5 storage,
solid state storage, NEC brand calibrated monitors, various brands of
monitor calibration colorimeters. Software included Intergraph Post
Processing Software (PPS) to handle camera raw images processed to virtual
frame panchromatic images and four band multispectral images. 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. SURDEX software was then used to fuse the high resolution pan
with the lower resolution multispectral image. This image was upsampled to
match the pan resolution using bilinear interpolation and converted to a
high resolution image via the Brovey Transform. GPS/IMU data was reduced to
projected coordinates in the appropriate UTM zone using the Applanix or IGI
office software. Aerial Triangulation was performed using Intergraph
ImageStation Automatic Triangulation (ISAT), ImageStation Digital
Mensuration (ISDM) and Photo-T bundle adjustment. SURDEX software was used
to determine the weak points in the AT construction point distribution.
SURDEX software was used to orthorectify the images.
SURDEX software
was used to compare overlapping orthoimages and correct 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 to cut in the best view of steep terrain. SURDEX software was
used to visually inspect master tiles for seam and image defects. For
Radiometry, SURDEX Grouping Tool was used to display large groups of images,
display individual and group histograms, and develop color correction
parameters to adjust image DN. 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 raw
images within the Image Metrics ranges. Grouping Tool was used again after
DOQQ to provide a quality assurance check.
Individual images may not
meet the USDA APFO Image Metrics ranges due to land cover. The goal was to
have the state as a whole meet the Image Metrics. To validate the accuracy
of the block adjustment derived from GPS, IMU, camera parameters and
conjugate point measurements photo identifiable ground control points will
be surveyed within each State. In Montana 2011, a total of 65 points were
utilized. These points will be surveyed by GPS techniques to produce
coordinates that are accurate to /- 0.25 meters RMSE in X,Y,Z. The GPS
surveying techniques utilized will assure that the coordinates are derived
in the required project datum and relative to an approved National Reference
System like OPUS. A report was generated to document the point locations,
their description, the final adjusted values and the derived positional
accuracy. The field surveying techniques may consist of static OPUS
observations, static GPS observations, real time differential GPS
observations and VRS observations. The control points were measured on
multiple photographs, initially solved as check points and the bundle was
rerun including all points as control. After the checkpoint run the
residual errors were reviewed to determine the quality of the solution with
only GPS and IMU based initial exterior orientation. 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. SURDEX
software was used to predict the horizontal error that results from DEM
error using AT construction points projected to the NED ground elevation.
As AT points are frequently on man-made and other vertical features not
includedin the DEM these ortho points can only be used to indicate regions
of error by the clusters of points that predict excessive horizontal
displacement. All products are reviewed by independent personnel prior to
delivery.
