Metadata: High Resolution Orthoimagery, Beltrami County, Minnesota, Spring 2020

High Resolution Orthoimagery, Beltrami County, Minnesota, Spring 2020

This page last updated: 08/17/2021
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:Beltrami County and Quantum Spatial, Inc.

Title: High Resolution Orthoimagery, Beltrami County, Minnesota, Spring 2020

Abstract: This dataset contains leaf-off 4-band red, green, blue, infrared (RGBI) digital orthophoto imagery produced at 9-inch resolution from new aerial photography captured in Spring 2020. The imagery covers Beltrami County, in northern Minnesota, except for the Red Lake Nation and far northern areas of the county.

This metadata record was created using information supplied by Quantum Spatial, Inc.

Purpose: These data depict geographic features on the surface of the earth. The dataset was created to produce current imagery data for Minnesota.

Time Period of Content Date: 05/2021

Currentness Reference: Imagery was flown May 4 - 7, 2020.

Progress: Complete

Maintenance and Update Frequency: None Planned

Spatial Extent of Data: Beltrami County, except Red Lake Nation and far northern areas of the county

Bounding Coordinates: -95.6374307916

Place Keywords: Minnesota, MN, Beltrami County

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: Unrestricted

Use Constraints: None. However, users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of their limitations. Acknowledgement of the organization providing these data to the public would be appreciated for products derived from these data.

MnGeo Redistribution conditions: In obtaining this data from the Minnesota Geospatial Information Office (MnGeo), it is understood that you and/or your organization have the right to use it for any purpose. If you modify it, you are encouraged to apply responsible best practices by documenting those changes in a metadata record. If you transmit or provide the data to another user, it is your responsibility to provide appropriate content, limitation, warranty and liability information as you see fit.

Contact Person Information: Kevin Trappe, GIS Director
Beltrami County
701 Minnesota Ave NW Ste. 219
Bemidji, MN  56601
Phone: 218-333-8457

Browse Graphic: Click to view a data sample.
Overview showing areas of the county that are covered by the imagery

Associated Data Sets: For information on other air photos available for Minnesota, see:

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: All GeoTIFF tagged data and image file sizes are validated using commercial GIS software to ensure proper loading before being archived. This validation procedure ensures correct physical format and field values for tagged elements. Seamlines and tile edges are visually inspected. Seamline mismatches are corrected unless the overall displacement is less than one pixel.

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.

The imagery covers Beltrami County except for the Red Lake Nation and far northern areas of the county.

Horizontal Positional Accuracy: The project specifications require that only horizontal accuracy be computed for orthoimagery files. The required accuracy meets or exceeds ASPRS standards. The horizontal accuracy was tested with 16 checkpoints located throughout the project area. These checkpoints were not used in the calibration or post-processing of the imagery data. The checkpoints were distributed throughout the project area and were surveyed using GPS techniques. See survey report for additional survey methodologies. The x and y positions of where the checkpoints fell on the orthoimagery were collected. These values were then compared to the surveyed control point x and y values.

Tested 0.196596 meters (0.65 feet) RMSEx. The RMSEx of the imagery was calculated using 16 independent checkpoints.

Tested 0.0920496 meters (0.3 feet) RMSEy. The RMSEy of the imagery was calculated using 16 independent checkpoints.

Tested 0.2170176 meters (0.71 feet) RMSEr. The RMSEr of the imagery was calculated using 16 independent checkpoints.

Vertical Positional Accuracy: There is no vertical component for orthophotos.

Lineage: Sources:

GPS Photo Control Survey: Quantum Spatial performed a geodetic control survey in support of the digital orthophoto production project. A total of 16 points were used for QC testing. Please see the survey report for more information.

Georeferenced Single Frames: Aerial imagery was acquired using a UltraCam Eagle M3 camera with a flight design that included a total of 26 flight lines. Aerial imagery was supplemented with the simultaneous acquisition of airborne GPS/IMU data, which captured the ground coordinate for the nadir point of each photograph. Aerial imagery was exposed at an altitude of 16100 feet above mean terrain.

Aerotriangulation: Softcopy aerotriangulation was performed utilizing the airborne GPS/IMU data, GPS ground control and image coordinate measurements allowing the direct computation of the exterior orientation parameters for each image of the project.

DEM: A compilation of topographic land form elevation datasets developed using in-house LiDAR data and data from the National Elevation Dataset for use in developing digital ortho imagery.

Process Steps - Quantum Spatial, Inc.

Imagery Acquisition: Digital aerial imagery was obtained using a UltraCam Eagle M3 camera equipped with Airborne GPS/IMU. A total of 26 flight lines were collected in the spring 2020 in multi-spectral (RGB-IR) format. The 0.75 foot imagery was acquired at an altitude above mean terrain of 16100 feet to yield a pixel resolution suitable for photogrammetric mapping and orthophoto production. The imagery was collected under conditions free from clouds and cloud shadows, smoke, fog, haze, light streaks, snow, ice on water bodies, flooding, excessive soil moisture, and foliage. The imagery consisted of blue, green, red, and infrared bands. Imagery for the photogrammetric mapping and digital orthophotos was captured according to task order specifications regarding, snow, haze, and cloud cover.

Ground Conditions: Imagery was collected in spring 2020, while no snow was on the ground and rivers were at or below normal levels.

Ground Control Point Collection: A total of 16 control points were established throughout the project area using a combination of conventional and GPS survey methods in order to support softcopy aerotriangulation and photogrammetric mapping meeting the accuracies specified in this Scope of Work. Ground control collection followed requirements set forth in the task order specifications. Please see the survey report for more information.

Aerotriangulation: Softcopy aerotriangulation was performed on one large block of imagery. The airborne GPS/IMU data, GPS ground control, and image coordinate measurements were utilized to allow the direct computation of the exterior orientation parameters for each image frame to support the photogrammetric process and orthophoto production.

Surface Creation: This process involved the development of seamless topographic landform elevation dataset utilizing in-house LiDAR data and data from the National Elevation Dataset to support the production of digital orthophotography that meet or exceed required orthophoto horizontal accuracy. The topographic features included a grid of elevation points and may include break lines that define ridges, valleys, edge of water, transportation features and abrupt changes in elevation. The final DEM is suitable for orthophoto production only (not suitable for contour generation). The DEM is used to then generate a Triangulated Irregular Network (TIN) to support orthophoto production. The final DEM used for orthophoto production was delivered in countywide rasters in a file geodatabase.

Orthophoto Processing: Utilizing all four bands [blue (B), green (G), red (R), and infrared (IR)] digital orthorectification was performed using bilinear interpolation algorithms resulting in a spatial and radiometric transformation of the digital image from line/sample space into NAD 1983 HARN Adj MN Beltrami South Feet, Foot US. The interior and exterior orientation parameters from the aerotriangulation process were used to project each pixel into the ground coordinate system, while the ortho grade DEM was used to correct for relief displacement. Radiometric correction software and techniques were used to create orthophoto files that minimize the appearance of image seams and without loss of feature signature. Orthophotos are checked for geometric accuracy, image quality, and are tonally balanced to produce a uniform contrast and tone across the entire project. The individual overlapping orthophoto frames were mosaicked together. The ortho photos meet ASPRS horizontal accuracy standards.

The data were developed based on a horizontal projection/datum of NAD 1983 HARN Adj MN Beltrami South Feet, Foot US. Imagery data were delivered to Beltrami County as 0.75 foot 8-bit 4-band (RGB-IR) GeoTIFF tiles and 8-bit 4-band (RGB-IR) MrSID mosaics (20:1 compression ratio). Tiled deliverables contained 174 individual tiles.

Process Steps - MnGeo

Beltrami County provided the imagery tiles to MnGeo which then reprojected the imagery from State Plane Coordinates to UTM coordinates, Zone 15, NAD83 and added it as a layer to the Geospatial Image Service.

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: .2286

Cell Height: .2286

Section 5: Attributes

Overview: Three band orthoimagery is organized in three color bands or channels which represent the red, green, and blue (RGB) portions of the spectrum. Four band orthoimagery is organized in four color bands or channels which represent the red, green, blue (RGB), and near infrared (IR) portions of the spectrum. Each image pixel is assigned a triplet or quadruplet of numeric values, one for each color band. Numeric values range from 0 to 255.

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: Minnesota Geospatial Information Office (MnGeo)

Publication Date: 05/21/2021

Contact Person Information: Nancy Rader, GIS Data Specialist
Minnesota Geospatial Information Office (MnGeo)
658 Cedar Street, Room 300
St. Paul, MN  55155
Phone: 651-201-2489

Distributor's Data Set Identifier: Beltrami Imagery 2020

Distribution Liability: 1. Beltrami County's disclaimer: This data is furnished on an 'as is' basis with no guarantee or representation about the accuracy, currency, suitability, performance, merchantability, reliability, or fitness of the data for any particular purpose. Beltrami County, MN shall not be liable for any direct, indirect, special, incidental, compensatory, or consequential damages or third party claims resulting from the use of this data. This disclaimer is provided pursuant to Minnesota Statutes 466.03, Subd. 21.

2. MnGeo's disclaimer:

Ordering Instructions: The imagery is available to view via WMS (Web Mapping Service) from MnGeo's Geospatial Image Service. The Minnesota Geospatial Image Service web pages provide the url to connect to the service as well as information about how to use a WMS. 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: 08/17/2021

Contact Person Information: Nancy Rader, GIS Data Specialist
Minnesota Geospatial Information Office (MnGeo)
658 Cedar Street, Room 300
St. Paul, MN  55155
Phone: 651-201-2489

Metadata Standard Name: Minnesota Geographic Metadata Guidelines

Metadata Standard Version: 1.2

This page last updated: 08/17/2021
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