Digital Orthoimagery, Twin Cities, Minnesota, Spring 2020, 1-ft Resolution
Go to Section:- Overview
- Data Quality
- Data Organization
- Coordinate System
- Attributes
- Distribution - Get Data
- Metadata Reference
Section 1: Overview
Originator:Metropolitan Council, Surdex Corporation
Title:
Digital Orthoimagery, Twin Cities, Minnesota, Spring 2020, 1-ft Resolution
Abstract:
This dataset contains leaf-off, 4-band (red, green, blue, near-infrared (RGBI)) digital orthophoto imagery of the Twin Cities metropolitan area in east-central Minnesota. 268 digital orthophoto quarter quadrangle (DOQQ) tiles were produced at 30-cm (1-foot) resolution from new aerial photography captured in the spring of 2020. DOQQ tiles covering Ramsey County were created from 15-cm imagery and resampled using Surdex proprietary up to 30-cm GSD data. The counties of Anoka, Carver, Dakota, Hennepin, Scott and Washington were captured at 30-cm resolution for Ortho production.
Project partners include Metropolitan Council, Minnesota Geospatial Information Office (MnGeo), Metropolitan Mosquito Control District and Ramsey County. This dataset is available for direct use via the MnGeo Geospatial Image Service (Twin Cities metro layer). More information at http://www.mngeo.state.mn.us/chouse/wms/geo_image_server.html.
This metadata record was created by Metropolitan Council using information supplied by Surdex Corporation, MnGeo and the Minnesota Department of Transportation.
Purpose:
To produce four-band, leaf-off digital ortho-rectified aerial photography acquired in the spring of 2020 for the purpose of updating generalized land use data for the Twin Cities metropolitan area as well as for many other mapping and analysis functions.
Time Period of Content Date:
04/01/2020
Currentness Reference:
Ground condition. Image acquisition dates: April 4, 5 and 10, 2020.
Progress:
Complete
Maintenance and Update Frequency:
The Metropolitan Council is required to collect Generalized Land Use data at the same time as the Census. The Metropolitan Council plans to acquire aerial imagery again in 2025.
Spatial Extent of Data:
7-county Twin Cities metro: Anoka, Carver, Dakota, Hennepin, Ramsey, Scott and Washington counties, Minnesota
Bounding Coordinates:
-94.34
-92.62
45.75
44.43
Place Keywords:
Minnesota, MN, Anoka, Carver, Dakota, Hennepin, Ramsey, Scott, Washington, Twin Cities
Theme Keywords:
imageryBaseMapsEarthCover, Orthophotography, Digital Orthophotography, Ortho, Orthophotos, Digital Orthorectified Images, Digital Orthophotos, DOQ, DOQQ, Imagery, Images, Aerial Photography, Aerial Photos, Digital Aerial Photography, Air Photo, Color Infrared, Four Band Imagery
Theme Keyword Thesaurus:
ISO 19115 Topic Category
Access Constraints:
None. This dataset is public domain under the Minnesota Government Data Practices Act (Minnesota Statutes Chapter 13). If the dataset is not available from the Online Linkage in Section 6, please contact the Distribution Contact Person.
Use Constraints:
None. This dataset is public domain under the Minnesota Government Data Practices Act (Minnesota Statutes Chapter 13).
Contact Person Information:
Tanya Mayer,
GIS Specialist
Metropolitan Council
390 Robert Street North
St. Paul,
MN
55101-1805
Phone: 651.602.1604
Email: tanya.mayer@metc.state.mn.us
Section 2: Data Quality
Attribute Accuracy:
N/A
Logical Consistency:
N/A
Completeness:
Created using native 30-cm GSD and resampled 15-cm GSD for a complete 30-cm resolution data set over 7 counties in the metropolitan Minneapolis/St. Paul area. The counties of Anoka, Carver, Dakota and Scott were originally collected at a 15-cm GSD and resampled to 30-cm. Imagery for Hennepin, Ramsey and Washington counties were originally collected at a 30-cm GSD.
Horizontal Positional Accuracy:
Meets the ASPRS horizontal accuracy standard for 30-cm GSD at Standard Mapping Accuracy of 60-cm adhering to NSSDA guidelines and specifications. Surdex collected new survey control in UTM NAD 1983(2011) Zone 15N, meters with Geoid model 12b, along with existing County Survey and Airborne GPS data at the time of image acquisition and was used exclusively to control the product to ground coordinates.
Surdex reported the horizontal positional accuracy, calculated using 58 control points, yielded an RMSE of 30.9-cm (1.01 feet). Those data were also tested for horizontal positional accuracy by MnDOT's Office of Land Management Survey and Mapping Section staff. A project area accuracy measure was calculated using 255 independent survey control points, yielding an RMSE of 42.97-cm (1.41 feet), meeting the ASPRS-specified threshold for Standard Mapping and GIS work of <=60-cm (1.97-feet).
Vertical Positional Accuracy:
None - this is a horizontal-only product.
Lineage:
Aircraft were deployed to the Twin Cities area in April 2020 for digital image acquisition during the requested time frame. Four Cessna Conquests equipped with a Leica ADS100 (Digital Mapping Camera) captured 4-band imagery over the entire project area of interest. Imagery was captured in a north-south direction at an altitude of 12,300' above mean terrain, at a sidelap of 30% for the bulk of the project area but sidelap was increased to 40% within the Developed Area defined by the Highway 494-694 loop. Sidelap was also increased to 60% over the Minneapolis and St. Paul Downtown Areas. Non north-south flight lines were added and acquired in-line with streets within and near the Downtown Areas. These lines were acquired very near to the peak sun angle for that day. A small amount of imagery was collected after a brief snow fall episode so lingering snow does exist in a few limited areas. The early spring conditions are evident with wet fields and minor high water in streams and rivers. The dates of image acquisition were 4/4/2020, 4/5/2020 and 4/10/2020.
Imagery for Anoka, Carver, Dakota, Hennepin, Scott and Washington counties were collected at a 30-cm GSD. Ramsey County was collected at a 15-cm resolution and resampled to 30-cm to complete the 7-county wide 30cm dataset.
Four bands (RGBI, natural color plus near infrared) of raw camera data were processed by Surdex using Leica X Pro software coupled with Surdex proprietary image handling software for color correction and dodging. Post processing of Airborne and Ground GPS data was performed with Waypoint Consulting's GrafNav software. Aerial Triangulation was completed in UTM NAD 1983 (2011) Zone 15N, using Leica X Pro Automatic Triangulation and rectification of imagery to the client supplied DEM was completed using Surdex proprietary software with LiDAR DEM provided by Minnesota IT Services. Image mosaicking, QC and final DOQQ tiled products were produced using proprietary Surdex software.
Shortly after orthoimagery production began Surdex provided two representative sample areas of data to project stakeholders for processing evaluation and standardization. This quality control pilot project allowed all subsequent processing to be controlled by client-established color balance parameters.
All post processed orthoimagery was systematically reviewed by stakeholders via Surdex's web-based Client Product Acceptance Tool (CPAT) which allowed edit calls to be communicated to the vendor online. Approximately 175 user edit calls were addressed. Upon repair and reexamination of all stakeholder edit calls, Surdex physically delivered the orthoimagery data on hard drive.
Surdex reported the horizontal positional accuracy, calculated using 58 control points, yielded an RMSE of 30.9-cm (1.01 feet). Those data were also tested for horizontal positional accuracy by MnDOT's Office of Land Management Survey and Mapping Section staff. A project area accuracy measure was calculated using 255 independent survey control points, yielding an RMSE of 42.97-cm (1.41 feet), meeting the ASPRS-specified threshold for Standard Mapping and GIS work of <=60-cm (1.97-feet).
The final data is in UTM NAD83 (2011) Zone 15 projection.
The original data was delivered in GeoTIFF format only.
The imagery is available to the general public only as a web map service (WMS) on MnGeo's Geospatial Image Service (see ordering instructions below).
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
Vertical Datum:
Vertical Units:
Depth Datum:
Depth Units:
Cell Width:
0.3
Cell Height:
0.3
Section 5: Attributes
Overview:
Imagery in 4 Bands with the order of Red, Green, Blue and Near Infrared.
Detailed Citation:
Table Detail:
Section 6: Distribution
Publisher:
Minnesota Geospatial Information Center (MnGeo)
Publication Date:
Contact Person Information:
Tanya Mayer,
GIS Specialist
Metropolitan Council
390 Robert Street North
St. Paul,
MN
55101-1805
Phone: 651.602.1604
Email: tanya.mayer@metc.state.mn.us
Distributor's Data Set Identifier:
base_metro_orthos_2020
Ordering Instructions:
These ortho images are very large and thus are not provided online for download. Instead, they are available to view as a web map service (WMS), part of MnGeo's Geospatial Image Service. Click on the link below for more information about the Geospatial Image Service and how to use web map services.
Section 7: Metadata Reference
Metadata Date:
12/01/2020
Contact Person Information:
Tanya Mayer,
GIS Specialist
Metropolitan Council
390 Robert Street North
St. Paul,
MN
55101-1805
Phone: 651.602.1604
Email: tanya.mayer@metc.state.mn.us
Metadata Standard Name:
Minnesota Geographic Metadata Guidelines
Metadata Standard Version:
1.2
