High Resolution Orthoimagery, Washington County, MN, Spring, 2013

This page last updated: 03/19/2015
Metadata created using Minnesota Geographic Metadata Guidelines

Go to Section:
1. Overview
2. Data Quality
3. Data Organization
4. Coordinate System
5. Attributes
6. Distribution - Get Data
7. Metadata Reference

Section 1 Overview
Originator Washington County
Title High Resolution Orthoimagery, Washington County, MN, Spring, 2013
Abstract This dataset consists of 0.15-meter (approximately 0.5-foot) natural color orthoimages covering Washington County. Data were collected by Aero-Metric, Inc. (now Quantum Spatial).
Purpose The purpose of this project was to collect high resolution, orthorectified images of Washington County.
Time Period of Content Date 05/2013
Currentness Reference ground condition; range of dates from 05/10/2013 to 05/23/2013
Progress Complete
Maintenance and Update Frequency Irregular
Spatial Extent of Data Washington County
Bounding Coordinates -93.048219
Place Keywords Minnesota, MN, Washington County
Theme Keywords imageryBaseMapsEarthCover, orthoimage, rectified photograph, rectified image, orthophoto, natural color orthophoto, image map, aerial photography, air photo
Theme Keyword Thesaurus ISO 19115 Topic Category
Access Constraints None
Use Constraints None. However, users should be aware that temporal changes may have occurred since this data set was collected and that some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations.
Contact Person Information John Baer,
Washington County Public Works
14949 62nd Street North
Stillwater, MN  55082
Phone: 651-430-6883
Email: john.baer@co.washington.mn.us
Browse Graphic None available
Associated Data Sets For information on other air photos available for Minnesota, see: https://www.mngeo.state.mn.us/chouse/airphoto/

Section 2 Data Quality
Attribute Accuracy Radiometry is verified by visual inspection of the digital orthophoto. Slight systematic radiometric differences may exist between adjacent orthoimage files; these are due primarily to differences in source image capture dates and sun angles along flight lines. These differences can be observed in an image's general lightness or darkness when it is compared to adjacent orthoimage file coverages. Tonal balancing may be performed over a group of images during the mosaicking process which may serve to lighten or darken adjacent images for better color tone matching.
Logical Consistency Orthophotos conform to the specifications set forth by Washington County.
Completeness Orthoimages are visually inspected for completeness to ensure that no gaps or image misplacements exist within and between adjacent images. These images are derived by mosaicking multiple images to ensure complete coverage. Source imagery is cloud free.
Horizontal Positional Accuracy Orthophotos meet or exceed the standard for horizontal (X,Y) position as Root Mean Square Error = Flying Height (5000 ft) / 10,000 = 0.56 feet, with a maximum horizontal deviation of (3 x RMSE) or +/- 1.5 feet. The horizontal positional accuracy value was 0.44 feet.

The horizontal accuracy of the orthorectified images is mainly determined by the quality of the DEM. The elevation data was existing LiDAR data provided by the state of Minnesota website. Airborne GPS/IMU data was used. All photo identifiable checkpoints were measured and compared to the surveyed checkpoints to determine the RMSE. All rectified chip overlap was checked for mismatch. Final imagery was cut into client supplied tiles for delivery.
Vertical Positional Accuracy None
Lineage Sources:

1. Minnesota LiDAR data, State of Minnesota: Used to provide ground elevations for orthorectification process. https://gisdata.mn.gov/dataset/elev-lidar-metro2011

2. Washington County Area Aerotriangulation, 8/2013, Aero-Metric, Inc.: Used to provide photo exterior orientations for orthorectification process.

Processing Steps (Aero-Metric)

The Zeiss DMC (Digital Mapping Camera) images were aerotriangulated to support digital ortho image production for the Washington County, MN project area. Ground check point data was provided by Washington County. The project was referenced to the North American Datum of 1983 (NAD83/96), in the Washington County projection horizontally and to the North American Vertical Datum of 1988 (NAVD88) vertically. Units were in US Survey Feet.

The imagery for this project was flown at a nominal acquisition altitude (AGL) of 4,800 feet. Differential baseline lengths were kept to a minimum by the use of the nearest available CORS stations to the project area. GPS coordinates were referenced to the National Spatial Reference System (NSRS) through connections to active CORS and/or passive monumented control stations. Digital camera(s) were calibrated by the manufacturer and the camera parameters refined through in-situ proprietary procedures.

The images, ABGPS/IMU data, and ground check point data were used as inputs to the INPHO Match-AT softcopy program. Match-AT correlated image points and aerotriangulated the block of images to create exposure station exterior orientations. All ground points were manually measured on the imagery. These points were included in the aerotriangulation adjustments for absolute ground location verification.

The scale of the aerial photos was 1 inch = 1016 feet. The photography was exposed on 5/10/13, 5/12/13, and 5/23/13.

Rectification was done in INPHO OrthoMaster using the aerotriangulation data, raw images, and existing LiDAR DEM data which was reviewed and edited by Aero-Metric. These rectified images were used to automatically generate seamlines which were then fully reviewed and edited. The rectified images were mosaicked, balanced, and cut into final image tiles. The final tiles were reviewed 100% and artifacts were removed as well as other edits performed. ECW compressed imagery was also generated per tile, township (40:1 compression), and county (70:1 compression) for delivery.

Software versions used: INPHO OrthoMASTER 5.5, INPHO Match-T 5.5, IRAS C ver 10.0, Photoshop ver CS5, Windows XP and Windows 7, INPHO OrthoVista 5.5, Global Mapper 13, Bentley MicroStation 7 and 8

Processing Steps (MnGeo)

The county provided the imagery to the Minnesota Geospatial Information Office. MnGeo staff reprojected the imagery from Washington County coordinates with 6-inch resolution to UTM Zone 15 coordinates with .15-meter resolution and created a WMS service to distribute the imagery.

This metadata record was compiled by MnGeo using information supplied by Aero-Metric and Washington County.

Section 3 Spatial Data Organization (not used in this metadata)

Section 4 Coordinate System
Horizontal Coordinate Scheme Universal Transverse Mercator
UTM Zone Number 15
Horizontal Datum NAD83
Horizontal Units meters
Cell Width .15
Cell Height .15

Section 5 Attributes
Overview Natural color orthoimagery is organized in three color bands or channels which represent the red, green, and blue portions of the spectrum. Each image pixel is assigned a triplet of numeric values, one for each color band. Numeric values range from 0 to 255. Areas where data is incomplete due to lack of full image coverage are represented with the numeric value of 0.
Detailed Citation U.S. Department of the Interior, U.S. Geological Survey, 1996, Standards for Digital Orthophotos: Reston, VA.
Table Detail:

Section 6 Distribution
Publisher Washington County, Minnesota
Publication Date 2013
Contact Person Information Nancy Rader, GIS Data Coordinator
Minnesota Geospatial Information Office (MnGeo)
658 Cedar Street, Room 300
St. Paul, MN  55155
Phone: 651-201-2489
Fax: 651-296-6398
Email: gisinfo.mngeo@state.mn.us
Distributor's Data Set Identifier Washington County 2013 Orthoimages
Distribution Liability MnGeo's full disclaimer is here: https://www.mngeo.state.mn.us/chouse/disclaimer.html
Ordering Instructions The imagery is available to view via WMS (Web Mapping Service) from MnGeo's Geospatial Image Server. The Minnesota Geospatial Image Service web pages provide the url to connect to the Geospatial Image Server as well as information about how to use WMS services. Due to file size there is currently no option to download the photos.

Access via the Minnesota Geospatial Commons by clicking on the 'Online Linkage" field below.
Online Linkage I AGREE to the notice in "Distribution Liability" above. Clicking to agree will either begin the download process, link to a service, or provide more instructions. See "Ordering Instructions" above for details.

Section 7 Metadata Reference
Metadata Date 03/19/2015
Contact Person Information Hollie Auchterlonie, Student Worker
Minnesota Geospatial Information Office (MnGeo)
658 Cedar Street, Room 300
St. Paul, MN  55155
Phone: 651-201-2496
Email: hollie.auchterlonie@state.mn.us
Metadata Standard Name Minnesota Geographic Metadata Guidelines
Metadata Standard Version 1.2
Metadata Standard Online Linkage https://www.mngeo.state.mn.us/committee/standards/mgmg/metadata.htm

This page last updated: 03/19/2015
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