City of Helena
Infotech Enterprises America (formerly VARGIS, LLC)
20070612
2006 Color Orthophotographs of Helena, Montana
remote-sensing image
Helena, MT
Montana State Library
http://apps.msl.mt.gov/Geographic_Information/Data/Aerial_Photos/helena_hrcolor_2006.aspx
Color orthophotographs of the City of Helena, photogrammetrically compiled from aerial photography flown in April 20, 2006.
Digital Orthophotographs serve a variety of purposes, from interim maps to field references for earth science investigations and analysis. The orthophotograph is useful as a layer of a geographic information system and as a tool for revising digital line graphs and topographic maps. City of Helena intends to utilize the orthophotographs to support their current planning and future development needs.
The project encompasses approximately 44 squares miles of the urban area in and around the City of Helena. The scale of the aerial photography negative was 1"=660' exposed at a flight height of 3,500 feet above mean ground level. The resolution for this orthophotograph is 0.0150 meter, or approximately 6 inches.
20060420
ground condition
As needed
-112.107746
-111.952715
46.648483
46.540116
ISO 19115 Topic Category
imageryBaseMapsEarthCover
City of Helena
Orthoimagery
Color
Aerial Photography
Imagery
Digital Image Map
True Orthophotographs
City of Helena
Montana
US
USA
None
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.
City of Helena
mailing and physical address
316 N. Park Ave.
Helena
Montana
59624
406-447-8389
espangenberg@co.lewis-clark.mt.us
During photographic reproduction of the source photographs, limited analog dodging is performed to improve image quality. Analog dodging consists of holding back light from certain areas of the sensitized photographic material to avoid overexposure. The diapositive is inspected to ensure clarity and radiometric uniformity. Diapositive image brightness values are collected with a minimum of image quality manipulation. Image brightness values may deviate from the brightness values of the original images because of image value interpolation during the scanning and rectification processes. Radiometry is verified by visual inspection of the digitalorthophoto quadrangle with the original unrectified image to determine if the digital orthophoto has the same or better image quality as the original unrectified input image. Slight systematic radiometric differences can be detected between adjacent DO files; these are due primarily to differences in source photograph capture dates and sun angles along flight lines when the aerial photographs were taken. These differences can be observed in an image's general lightness or darkness when it is compared to adjacent DO file coverages.
All Digital Orthophotograph (DO) header data and image file sizes are validated using USGS software before being archived. This validation procedure ensures correct physical format and field values for header elements. Logical relationships between header elements are tested.
DO images are visually inspected for completeness to ensure that no gaps or image misplacements exist. DO's are cloud free within the image area. Some clouds may, very infrequently, appear in the overedge coverage.
The City of Helena area horizontal positional accuracy and the assurance of that accuracy depend, in part, on the accuracy of the data inputs to the rectification process. These inputs consist of the digital elevation model (DEM),aerotriangulation control and methods, the photo source camera calibration, scanner calibration, and aerial photographs that meet National Aerial Photography Program (NAPP) standards.
The vertical accuracy of the verified DEM is equivalent to or better than 1" = 100', with a root mean square error (RMSE) of no greater than 1/10000 of the flying heigth. Field control is acquired by second order class 1 or better survey methods sufficiently spaced to meet National Map Accuracy Staandards (NMAS) for 1:1,000-scale products.
The production procedures, instrumentation, hardware and software described here are specific to the production of the City of Helena area referenced in this document. The rectification process requires, as input, a user parameter file to control the rectification process, a digital elevation model (DEM) gridded to user specified bounds, projection, zone, datum and X-Y units, a scanned digital image file (PHOTO) covering the same area as the DEM, ground X-Y-Z point values (CONTROL) and their conjugate photo coordinates in the camera coordinate system, and measurements of the fiducial marks (CAMERA) in the digitized image.
The camera calibration report (CAMERA) provides the focal length of the camera and the distances in millimeters from the camera's optical enter to the camera's 8 fiducial marks. These marks define the frame of reference for spatial measurements made from the photograph.
Ground control points (CONTROL) supplemented with ABGPS and developed in a triangulation, are second order class 1, and meet National Map Accuracy Standard (NMAS) for 1:1,000-scale. Ground control points are in the City of Helena specified projection / datum / unit of measure. Horizontal and vertical residuals of aerotriangulated tie-points are equal or less than 1/10000 of the flying height.
Standard aerotriangulation passpoint configuration consists of 32 ground control points, one near each corner, one at the center near each side and 1 near the center of the photograph, are used. The conjugate positions of the ground control points on the photograph are measured and recorded in camera coordinates.
The raster image file (PHOTO) is created by scanning an aerial photograph film diapositive with a precision image scanner (ZEISS scanner). An aperture of 14 microns is used. The elevation data source (DEM) is derived from the photography (PHOTO) using softcopy stereoplotter workstations. All DEM data is equivalent to or better than 1" = 100'.
A DEM covering the extent of the photograph is used for the rectification. The DEM is traversed from user-selected minimum to maximum X-Y values add the DEM X-Y-Z values are used to find pixel coordinates in the digitized photograph using transformations mentioned above. For each raster image cell subdivision, a brightness value is obtained using nearest neighbor, bilinear, or cubic convolution resampling of the scanned image. The pixel processing algorithm is indicated in the header file. An inverse transformation relates the image coordinates referenced to the fiducial coordinate space back to scanner coordinate space.
Rectification Process:
The photo control points and focal length are interactively fitted to their conjugate ground control points using a single photo space resection equation using Instantaneous Simultaneous Bundle Block Adjustment (ISBBA). From this mathematical fit is obtained a rotation matrix of constants about the three axes of the camera. This rotation matrix can then be used to find the photograph or camera coordinates of any other ground X-Y-Z point. Next a two dimensional fit is made between the measured fiducial marks on the digitized photograph and their conjugate camera coordinates. Transformation constants are developed from the fit and the camera or photo coordinates are used in reverse to find their conjugate pixel coordinates on the digitized photograph.
Quality Control:
All data is inspected according to a quality control plan submitted by Infotech Enterprises America; formerly VARGIS, LLC and approved.
Raster
Pixel
77827
76680
1
State Plane Coordinate System
2500
45.000000
49.000000
-109.500000
44.250000
600000.000000
0.000000
row and column
0.150000
0.150000
meters
D_North_American_1983_HARN
Geodetic Reference System 80
6378137.000000
298.257222
Montana State Library
mailing address
PO Box 201800
Helena
MT
59620-1800
406-444-5354
406-444-4799
406-444-0266
geoinfo@mt.gov
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.
Downloadable Data
MrSID
http://apps.msl.mt.gov/Geographic_Information/Data/Aerial_Photos/helena_hrcolor_2006.aspx
20140106
20130719
20130417
20070611
City of Helena
mailing and physical address
316 N. Park Ave.
Helena
Montana
59624
406-447-8389
espangenberg@co.lewis-clark.mt.us
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998
{97E297AB-F65B-4016-9C21-EDF01ADC8313}