Metadata for Lower Gallatin Valley Color Infrared Orthophotos, 2001
Identification Information:
Citation:
Originator: Gallatin Local Water Quality District
Publication date: 06/12/2006
Title: Lower Gallatin Valley Color Infrared Orthophotos, 2001
Publication place: Helena, Montana
Publisher: Montana State Library
Online linkage: http://apps.msl.mt.gov/Geographic_Information/Data/Aerial_Photos/gallatin_colinf_2001.aspx
Larger Work Citation:
Originator: Gallatin Local Water Quality District
Publication date: 06/2004
Title: Wetland and Riparian Assessment of the Gallatin Valley
Publication place: Bozeman, MT
Publisher: Gallatin Local Water Quality District
Online linkage: http://www.gallatin.mt.gov/Public_Documents/GallatinCoMT_WQDReports

Abstract:
These data are digital aerial photos, taken on September 9, 2001. They consist of 41 tiles that cover the lower Gallatin Valley in Montana. They are orthorectified color infrared MrSID images with a ground resolution of 2 feet, and they are registered to the Montana State Plane coordinate system, NAD83, units meters.

These images were produced for the Gallatin Local Water Quality District. The photography was flown by Montana Aerial Photography of Missoula, the photographs were scanned by Michael Baker Jr., Inc of Beaver, PA, and the orthophotos were produced by GISPix of Bozeman.
Purpose:
These aerial photographs were captured to support the Wetland and Riparian Assessment of the Gallatin Valley, to show the status of wetlands in the Gallatin Valley in 2001.

Time period of content:
Calendar date: 09/09/2001
Currentness reference: ground condition
Status:
Progress: Complete
Maintenance and update frequency: None planned
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.
Point of contact:
Montana State Library
PO Box 201800
Helena, MT 59620-1800


Telephone: 406-444-5354
TDD/TTY telephone: 406-444-4799
Fax: 406-444-0266
E-Mail: geoinfo@mt.gov


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Data Quality Information:
Horizontal Positional Accuracy Report:
Ground control came entirely from points on USGS digital orthophoto quadrangles (DOQs). The horizontal accuracy of a DOQ, following the National Map Accuracy Specifications, is that 90% of the points within the image are within 40 feet of true position. A total of 1082 ground control points were used for the project area, providing an even distribution of control throughout the project area.

The root mean square value (RMS) for the project area was 1.27 meters in the X direction and 1.28 meters in the Y direction. The highest RMS value for a ground control point accepted in the model was 5 meters, (in a few locations where there was a large discrepancy in accuracy between overlapping DOQs). 1075 tie points were collected between the images to cross-rectify them, to help the computer recognize where the photos overlap, and to provide another point of reference used in the math model. The RMS score for the tie points scored as 0.10 meters in the X direction and 0.07 meters in the Y direction. As a quality assurance measure, after every three flight lines, the residual report generated by the model was examined, points with an RMS value greater than 5 meters were either relocated or deleted.

Lineage:
Source information:
Originator: Montana Aerial Photography
Publication date: Unpublished Material
Title: Aerial Photography
Other citation details:
These were 9-inch by 9-inch color infrared photographs taken on September 9, 2001, printed at a scale of 1:24,000.
Source scale denominator: 24000
Source contribution: These are the raw images the orthophotos were created from
Calendar date: 2005

Process step:
The photographs were scanned with a high-resolution photogrammetric scanner at 907 dots per inch.
Process contact:
Michael Baker Jr., Inc.
4301 Dutch Ridge Road
Beaver, PA 15009


Telephone: 724-495-7711


Process step:
The type of digital photogrammetry used to orthorectify the imagery is referred to as aerotriangulation. The math model used in the correction uses the principles of triangulation to correct the photography in the x and y direction and incorporates the use of a digital elevation model (DEM) for the vertical (z) direction. With PCI Geomatics' OrthoEngine, a block bundle adjustment in the math model is used to "bridge" the control points used on surrounding photos together as if they are one large image.

The first step in aerotriangulation is to create an interior orientation by registering the fiducial marks of the photograph. At the start of the project a camera calibration report (a very accurate description of the different types of distortion associated with the camera used to take the pictures) is entered into the system. The computer then uses the measurements taken from the fiducial marks and computes them against the camera calibration report to create the "interior orientation" of the block model. For each image an interior orientation is calibrated, with all of the RMS values scoring a similar value, as the photogrammetric scanner used to scan the photography is a precise instrument preserving positional accuracy.

The majority of time spent on the project is spent obtaining ground control and tie points used to calculate the exterior orientation of the model. The ground control came entirely from points on USGS digital ortho-quadrangles (DOQs). I used a total of 1082 ground control points for the project area, providing an even distribution of control throughout the project area. I have learned after the fact that I did not need to collect such a large number of ground control points (GCPs) because of the "bridging" characteristic of the block bundle adjustment. The highest root-mean-square (RMS) error value for a GCP I accepted in the model was 5 meters, (in a few locations where there was a large discrepancy in accuracy between overlapping DOQs). The other labor intensive step was to obtain tie points between the images, for which I collected a total of 1075. Tie points also help the computer recognize where the photos overlap and provide another point of reference used in the math model. As a quality assurance measure, after every three flight lines I would look at the residual report generated by the model and either relocate or delete points with an RMS value greater than 5 meters. After GCPs and tie points were collected, the model is ready to generate ortho-photos.

The orthogeneration process creates a single image at a time representing a subsetted area of each individual scanned image. The image created is a subset of the entire scanned photo so as to use only the most accurate portion of an aerial photograph (which is a towards the center) and so as not to include the periphery features as fiducial marks in the image. It was possible to subset considerably as there was an average of 60% endlap and 30% sidelap for the photographs, with just two exceptions in the lower mountain regions. I chose to use a nearest neighbor resampling method as to most accurately preserve the value associated with the pixel. The drawback of using the nearest neighbor method is a slightly jagged appearance that linear features can have after the resampling, however after examining the results of the other two resampling methods, I deemed the nearest neighbor method most appropriate for this project. The digital elevation model (DEM) used in the model for the vertical positioning came from the USGS NED-DEM data site and had a 30 meter pixel resolution. The DEM is used in the math model to adjust the horizontal position geometrically, adjusting the position for the topographic displacement. As a quality control measure for the project, each individual image created was swiped with a DOQ covering the area to examine for inconsistencies in the images. The most common source of error came from points that were sharing overlapping positions on DOQs.

After the individual photos were created the images were mosaiced to create an image for each USGS 7.5-minute quadrangle that covers the project area. The mosaicing is generally an automated process where I chose the images to be used and the computer would perform the difficult task of choosing the best possible cutlines in the overlapping images to most effectively produce a "seamless" appearance to the mosaiced image. The computer would also effectively choose a portion in overlapping photos that would have a higher value, eliminating shadows where possible and choosing the brighter values.
Process contact:
David Moody
GISPix
1426 Ash Drive
Bozeman, MT 59715-5901


Telephone: 406-581-4539
E-Mail: dmoody@gispix.com


Process step:
The orthophoto quadrangles provided by GISPix were converted from UTM zone 12 coordinates, compressed to MrSID format, and were clipped and mosaiced to form 41 smaller tiles, each approximately 7750 by 6500 meters.
Process date: 06/09/2006
Process contact:
Montana State Library
PO Box 201800
Helena, MT 59620-1800


Telephone: 406-444-5354
TDD/TTY telephone: 406-444-4799
Fax: 406-444-0266
E-Mail: geoinfo@mt.gov


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Spatial Data Organization Information:
Raster object information:
Raster object type: Pixel
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Spatial Reference Information:
Horizontal coordinate system definition:
Grid coordinate system name: State Plane Coordinate System 1983
SPCS zone identifier: 2500
Lambert conformal conic:
Standard parallel: 45
Standard parallel: 49
Longitude of central meridian: -109.5
Latitude of projection origin: 44.25
False easting: 600000.00000
False northing: 0.00000
Planar distance units: meters
Geodetic model:
Horizontal datum name: North American Datum of 1983
Ellipsoid name: Geodetic Reference System 80
Semi-major axis: 6378137
Denominator of flattening ratio: 298.257
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Entity and Attribute Information:
Entity and attribute overview:
24-bit pixels, 3 band color (RGB) represent brightness values 0 - 255
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Distribution Information:
Distributor:
Montana State Library
PO Box 201800
Helena, MT 59620-1800


Telephone: 406-444-5354
TDD/TTY telephone: 406-444-4799
Fax: 406-444-0266
E-Mail: geoinfo@mt.gov


Resource description: Downloadable Data


Distribution liability:
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.

Standard order process:
Digital form:
Format name: MrSID Generation 2
Online option:
http://apps.msl.mt.gov/Geographic_Information/Data/Aerial_Photos/gallatin_colinf_2001.aspx
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Metadata Reference Information:
Metadata date: 07/19/2013
Metadata review date: 04/17/2013
Metadata review date: 06/12/2006
Metadata contact:
Montana State Library
PO Box 201800
Helena, Montana 59620-1800


Telephone: 406-444-5354
TDD/TTY telephone: 406-444-4799
Fax: 406-444-0266
E-Mail: geoinfo@mt.gov


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