LiDAR Elevation, Blue Earth County, Minnesota, 2012

This page last updated: 03/13/2014
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 AeroMetric, Inc. and Minnesota Department of Natural Resources
Title LiDAR Elevation, Blue Earth County, Minnesota, 2012
Abstract The project vendor, AeroMetric, Inc., acquired highly accurate Light Detection and Ranging (LiDAR) elevation data for Blue Earth County in south central Minnesota in Spring 2012. The project area consists of approximately 2,260 square kilometers (862 square miles). LiDAR data are in the UTM Zone 15 coordinate system, NAD83 (HARN) NAVD88 (Geoid09), meters. The tiling scheme is 16th USGS 1:24,000 quadrangle tiles.

The vendor delivered the data to the Minnesota Department of Natural Resources (DNR) in several formats:

1) One-meter digital elevation model
2) Edge-of-water breaklines
3) Classified LAS formatted point cloud data

DNR staff created two additional products: two-foot contours and building outlines.

Note: This metadata record was created at the Minnesota Geospatial Information Office by combining information supplied by AeroMetric and DNR.
Purpose The Minnesota Elevation Mapping Project was initiated to support the development of high accuracy land surface information for the purposes of improving water quality, flood emergency preparedness and response, floodplain mapping, transportation planning and design, recreational planning and design, urban planning and to provide more efficient and effective project planning and execution. This project was funded by the Clean Water Fund of the Clean Water, Land and Legacy Amendment.

The project consisted of acquisition, post-processing, and classification of LiDAR data and creation of products derived from the acquired data.
Time Period of Content Date 04/06/2012
Currentness Reference Date LiDAR data was collected.
Progress Complete
Maintenance and Update Frequency Unknown
Spatial Extent of Data Blue Earth County in south central Minnesota
Bounding Coordinates -94.382
-93.763
44.267
43.845
Place Keywords Blue Earth County, Minnesota
Theme Keywords elevation, LiDAR, DEM, digital elevation model, contour, topographic, topo, DTM, LAS, breakline
Theme Keyword Thesaurus ISO 19115
Access Constraints None
Use Constraints 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. Acknowledgment of the Minnesota Department of Natural Resources would be appropriate for products derived from these data.

See Disclaimer field for complete use conditions.
Contact Person Information Rob Merry,
AeroMetric, Inc.
4020 Technology Parkway
Sheboygan, WI  53083
Phone: 920-457-3631
Fax: 920-457-0410
Email: rmerry@aerometric.com
Browse Graphic None available
Associated Data Sets 1. Blue Earth County LiDAR Elevation 2005: www.mngeo.state.mn.us/chouse/metadata/lidar_blueearth2005.html

2. For more information about elevation data for Minnesota, see: www.mngeo.state.mn.us/chouse/elevation/index.html

Section 2 Data Quality
Attribute Accuracy See Vertical Positional Accuracy field
Logical Consistency None
Completeness Complete
Horizontal Positional Accuracy Airborne data has been compared with ground survey check points to determine positional accuracy. The dataset was acquired in four missions covering approximately 2,260 square kilometers (862 square miles) from an altitude of 2400 meters above ground level (AGL) and has a horizontal accuracy of 0.44 meters (per manufacturers system specifications).

Horizontal datum: NAD83 (HARN)
Vertical Positional Accuracy The Fundamental Vertical Accuracy (FVA) of the Classified Bare Earth for the Blue Earth data set achieved 11.4 cm (at 95% confidence level) in the "Open Terrain" land cover category. 26 control points were used in this evaluation.

Vertical accuracy was to achieve a RMSE Z of 12.5 cm (95% confidence level of less than 24.5 cm) or better in the "Open Terrain" land cover category for all areas in accordance with NDEP and ASPRS methodologies. Accuracy statement is based on areas of moderate to flat terrain. Diminished accuracies are to be expected in areas in dense vegetation. The accuracy of the LiDAR data as tested met or exceeded the vertical accuracy requirements, however, derived products may be less accurate in areas of dense vegetation due to a lesser number of points defining the bare-earth in such areas.

Minnesota Dept. of Natural Resources staff tested the vertical accuracy and concluded: "While the consolidated RMSE for this project area exceeds project standards by a small degree the data was approved due to the fact that the most egregious errors are in the forested category. Based on comparisons with aerial photography it was noted that the points most in error are in heavily forested areas. The lack of pictures of ground cover for the validation points makes it difficult to impose contract limitations. USGS specifications state that the forestry category is negotiable. Based on the quality of the other categories it was deemed acceptable." The full report is online: ftp.lmic.state.mn.us/pub/data/elevation/lidar/county/blueearth/2012/blue_earth_county_validation_report.pdf

Vertical datum: NAVD88 (Geoid09)
Lineage LiDAR data and derivative products produced in compliance with this task order are part of the data to be obtained under Contract number E112-10821 with Minnesota Department of Natural Resources. Specifications listed below are based on National Digital Elevation Program (NDEP) and the American Society for Photogrammetry and Remote Sensing (ASPRS) and Other High Quality Digital Topography.

AEROMETRIC, INC. PROCESSING INFORMATION:

This LiDAR data set consists of approximately 2,260 square kilometers (862 square miles). The airborne GPS and IMU data were processed immediately following each mission. In addition, a sample of the LIDAR data was post-processed at the completion of each mission and the data was reviewed to ensure planned data quality and coverage.

The LiDAR data was captured using a twin engine fixed wing aircraft equipped with a LiDAR system. The LiDAR system includes a differential GPS unit and inertial measurement system to provide highly accurate positioning.

Acquisition parameters:
1. Scanner - Leica ALS70
2. Flight Height - 2400 meters above ground level
3. Swath Width - 40 degrees
4. Sidelap - 30 percent
5. Nominal Point Spacing - 1.4 meters

GPS and IMU processing parameters:
1. Processing Programs and version - TerraTec TerraPOS, TPAS TC GNSS/INS Processor version 3.10, IPAS Pro version 2.01.02
2. IMU processing monitored for consistency and smoothness - Yes

Point Cloud Processing:
1. Program and version - ALS Post Processor version 2.74 build#9
2. Horizontal Datum - NAD83 HARN
3. Horizontal Coordinates - UTM zone 15N, in meters
4. Vertical Datum - NAVD88 (Geoid09)
5. Geoid Model used to reduce satellite derived elevations to orthometric heights - Geoid09 (Meters)

LIDAR Processing:
1. Processing Programs and versions - ALS Post Processor version 2.74 build#9, TerraSolid TerraScan (version 012.010), TerraModeler (version 012.005 and TerraMatch (version 012.004) and Intergraph MicroStation (version.08.05.02.70).
2. Point Cloud data was imported to TerraScan in a Microstation V8 (V) CAD environment on a specified tiling scheme based on the US National Grid Square.
3. Analyzed the data for overall completeness and consistency. This was to ensure that there were no voids in the data collection.
4. QC (Quality Control) for calibration errors in the dataset. This was accomplished by sampling the data collected across all flight lines and classifying the individual lines to ground. The software used the ground-classified lines to compute corrections (Heading, Pitch, Roll, and Scale).
5. Orientation corrections (i.e. Calibration corrections) were then applied (if needed) to the entire dataset.
6. Automatic ground classification was performed using algorithms with customized parameters to best fit the project area. Several areas of varying relief and planimetric features were inspected to verify the final ground surface.
7. AeroMetric, Inc. provided Quality Assurance and Quality Control (QAQC) data for this project. AeroMetric processed QA/QC points in 'open terrain' land cover category that were used to test the accuracy of the LiDAR ground surface. TerraScan's Output Control Report (OCR) tool was used to compare the QAQC data to the LIDAR data. This routine searches the LIDAR dataset by X and Y coordinate, finds the closest LIDAR point and compares the vertical (Z) values to the known data collected in the field. Based on the QAQC data, a bias adjustment was determined, and the results were applied to the LIDAR data. A final OCR was performed on the entire data set to assess any adjustment and ensure that data was accurately positioned.
8. Once the automatic processing and testing of LiDAR was complete, Aerometric meticulously reviewed the generated bare-earth surface data to insure that proper classification was achieved. Each tile was reviewed for accuracy and consistency of the macro ground classification. Also during this phase, MicroStation was used to generate linework representing water bodies and rivers. Separate linework was also placed in instances where overpasses had blocked enough valid ground returns or water gave too few ground returns to reasonably portray the ground surface. A proprietary in-house software program was then run to drape the river linework in a flowing fashion. Contours were generated on the river breaklines to review monotonicity of the draped linework.
9. After the LiDAR data was finalized for vertical placement, a macro was run via TerraScan to output a dataset generated on a per swath basis as part of the final deliverables. All points of the swath were reclassified to class 0 during this step.
10. Final deliverables were generated and output to a client-specified tiling scheme set of geodatabases.

DEM Processing:
1. After review of bare-earth surface data and breakline generation was completed, final DEMs were produced to a client-specified tiling scheme.
2. Using TerraModeler, DEMs were generated in an ASCII format on a per tile basis. These DEM were reviewed using GlobalMapper for adherence and completeness to the data and tile layout used during the creation process.
3. Following review acceptance, the ASCII files were processed into a FLOAT format. These files were converted using ArcMap to the delivered IMG format.


DNR PROCESSING INFORMATION

Additional products generated by Minnesota DNR staff are in the geodatabase for each of the tiles:

1. Two-foot contours were created by resampling the 1-meter DEM to 3 meters, then smoothing the 3-meter grid using a neighborhood average routine, and then creating contours from this surface using standard ArcGIS processing tools.

2. Building outlines were created by extracting from the LAS files those points with Classification 6 (buildings), then grouping those points within 3 meters of each other into a single cluster and then creating an outline around those points. This was done using standard ArcMap tools.

3. Hillshades were created from the one- and three-meter DEMs using standard ArcMap tools. Azimuth value = 215, Altitude = 45, Z-Factor = 1

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

Section 5 Attributes
Overview
Detailed Citation
Table Detail:

Section 6 Distribution
Publisher Minnesota Department of Natural Resources
Publication Date 12/10/2012
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 Blue Earth LiDAR 2012
Distribution Liability 1. Minnesota Department of Natural Resources General Geographic Data License Agreement is online: www.dnr.state.mn.us/sitetools/data_software_license.html

2. MnGeo's data disclaimer is online: www.mngeo.state.mn.us/chouse/disclaimer.html
Ordering Instructions The LiDAR data provided by DNR may be viewed online or downloaded in several ways:

1. MnTOPO website: www.dnr.state.mn.us/maps/mntopo/index.html

- view data online
- download data in Esri and open formats (tiles for most data formats will be mosaicked together during download)
- see the help file for details: files.dnr.state.mn.us/aboutdnr/gis/mntopo/mntopo_help_document.pdf


2. MnGeo's FTP site
Use the tile_index.pdf maps to locate the tiles you need. Except for the county file, tiles will not be mosaicked.

a. From the county folder: ftp.lmic.state.mn.us/pub/data/elevation/lidar/county/blueearth/
The county mosaic is named elevation_data.gdb.zip It is more than 7 gigabytes. For details of its contents and size, see this table: geoint.lmic.state.mn.us/lidar.php

b. In the 250k tiles folder: ftp.lmic.state.mn.us/pub/data/elevation/lidar/q250k/


For more help with Minnesota's LiDAR data, see www.mngeo.state.mn.us/chouse/elevation/lidar.html
Online Linkage I AGREE to the notice in "Distribution Liability" above. Clicking to agree will either begin the download process or link to download information. See "Ordering Instructions" above for details.

Section 7 Metadata Reference
Metadata Date 03/13/2014
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
Metadata Standard Name Minnesota Geographic Metadata Guidelines
Metadata Standard Version 1.2
Metadata Standard Online Linkage http://www.mngeo.state.mn.us/committee/standards/mgmg/metadata.htm


This page last updated: 03/13/2014
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