LiDAR Elevation, Twin Cities Metro Region, Minnesota, 2011

This page last updated: 04/28/2014
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 Fugro Horizons, Inc. and the Minnesota Department of Natural Resources
Title LiDAR Elevation, Twin Cities Metro Region, Minnesota, 2011
Abstract Fugro Horizons Inc. acquired highly accurate Light Detection and Ranging (LiDAR) elevation data for the Twin Cities metropolitan region in east-central Minnesota in Spring and Fall 2011, with some reflights in Spring 2012. The data cover Anoka, Benton, Carver, Dakota, Goodhue, Hennepin, Isanti, Kanabec, Meeker, Mille Lacs, Morrison, Ramsey, Scott, Sherburne and Washington counties.

Most of the data was collected at 1.5 points/square meter. Smaller areas were collected with 2 points/square meter and with 8 points/square meter:
1. 1.5 points/square meter covers Morrison, Mille Lacs, Benton, Isanti, Sherburne, Anoka, Meeker, Hennepin, Washington, Carver, Scott, and Goodhue counties.
2. 2 points/square meter covers the Dakota Block (southern 2/3 of Dakota County)
3. 8 points/square meter covers portions of Minneapolis/St. Paul and the City of Maple Grove
See map of block boundaries: lidar.dnr.state.mn.us/documentation/status/metro_data_delivery_dates.pdf

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 quality-checked the data and created three additional products: two-foot contours, building outlines and hillshades.

Note: This metadata record was created at the Minnesota Geospatial Information Office using information supplied by the vendor and by 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 primarily funded by the Clean Water Fund of the Clean Water, Land and Legacy Amendment.

For more about the Project, see: www.mngeo.state.mn.us/committee/elevation/mn_elev_mapping.html
Time Period of Content Date 2011
Currentness Reference Spring and Fall 2011 and Spring 2012.

Dates for specific blocks (map of block boundaries: lidar.dnr.state.mn.us/documentation/status/metro_data_delivery_dates.pdf )

Block A: 5-11-11 to 5-15-11
Block B: 5-11-11 to 5-15-11
Block C: 5-10-11
Block D: 4-29-11 to 5-8-11
Block E: 4-25-11
Block F: 11-13-11 to 11-17-11, reflight 3-25-12
Block G: 11-11-11 to 11-12-11, reflight 3-24-12
Block H: 11-12-11 to 11-13-11, reflight 3-28-12
Block X (a section that had to be reflown because of inadequate overlap of flight lines): 4-25-11 and 11-15-11, reflight 3-24-12 to 3-28-12

Dakota Block: 11-12-11 to 11-15-11
Metro Block and Maple Grove Block: 11-02-11 to 11-15-11
Progress Complete
Maintenance and Update Frequency As needed
Spatial Extent of Data Twin Cities metropolitan region, Minnesota
Bounding Coordinates 94.714600
92.120234
46.395540
44.211950
Place Keywords Minnesota, MN, Anoka, Benton, Carver, Dakota, Goodhue, Hennepin, Isanti, Kanabec, Meeker, Mille Lacs, Morrison, Ramsey, Scott, Sherburne, Washington counties
Theme Keywords elevation, LiDAR, DEM, digital elevation model, contour, topographic, topo, DTM, LAS, breakline
Theme Keyword Thesaurus ISO 19115
Access Constraints All data is in the public domain and there are no access constraints.
Use Constraints See Disclaimer field for complete use conditions.
Contact Person Information Tim Loesch, GIS Section Manager
Minnesota Department of Natural Resources
500 Lafayette Rd
St. Paul, MN  551554011
Phone: 651-259-5475
Email: tim.loesch@state.mn.us
Browse Graphic None available
Associated Data Sets For more information about elevation data for Minnesota, see: www.mngeo.state.mn.us/chouse/elevation/index.html

Section 2 Data Quality
Attribute Accuracy GPS phase data was post processed with continuous kinematic survey techniques using "On the Fly" (OTF) integer ambiguity resolution. The GPS data was processed with forward and reverse processing algorithms. The results from each process, using the data collected at the airport and in project area, were combined to yield a single fixed integer phase differential solution of the aircraft trajectory. The differences between the forward to reverse solution within the project area were within project specifications, indicating a valid and accurate solution. An IMU was used to record precise changes in position and orientation of the LIDAR scanner at a rate of 200 Hz. All IMU data was processed post flight with a filter to integrate inertial measurements and precise phase differential GPS positions. The resulting solution contains geodetic position, omega, phi, kappa, and time for subsequent merging with the laser ranging information.
Logical Consistency All deliverables were quality checked by MN DNR and passed inspection.
Completeness Complete
Horizontal Positional Accuracy Meets or exceeds horizontal accuracy of 0.6m RMSE. The NAD83 (HARN) datum was used.
Vertical Positional Accuracy The NAVD88 (Geoid09) vertical datum was used.

REPORT FROM THE VENDOR:

Vertical accuracy of the LiDAR data will be assessed and reported in accordance with the guidelines developed by the NDEP (National Digital Elevation Program) and subsequently adopted by the ASPRS (American Society for Photogrammetry and Remote Sensing). The complete guidelines may be found in Section 1.5 of the www.ndep.gov/NDEP_Elevation_Guidelines_Ver1_10May2004.pdf

Vertical accuracy requirements using the NDEP/ASPRS:

1. 1.5 points/square meter areas:
Sub-Project A 24.5cm ACCz, 95% (12.5cm RMSEz)

2. The higher density areas (Dakota Block, Metro Block and Maple Grove Block):
17.64cm ACCz 95% (9.0cm RMSEz)

REPORTS FROM MINNESOTA DNR:

True accuracy values:
Metro Block - 5 cm
Dakota Block - 10.8 cm
Maple Grove Block - 8.3 cm

See the complete Vertical Validation Reports in each folder on the data download FTP site; for example, the report for the Maple Grove Block is here: ftp.lmic.state.mn.us/pub/data/elevation/lidar/projects/metro/block_maple_grove/maple_grove_vertical_validation_report.pdf
Lineage VENDOR PROCESSING STEPS:

(See map of block boundaries: lidar.dnr.state.mn.us/documentation/status/metro_data_delivery_dates.pdf )

1. Specifications for Blocks A-H (1.5 points/square meter):

The settings for the Leica sensor ALS50-II MPiA included acquisition at 6,600' AMT, 130 knots, pulse rate 99,500Hz, scan rate 27.28Hz, 40 degree field of view, 4,805ft swath width, maximum along track spacing (occurs at FOV edge) of 2.45m in overlap areas, maximum cross track spacing (occurs at Nadir) 1.24m, 3sigma post spacing of 1.4m and 3sigma point density of 0.65 points per square meter. This sensor was also equipped with IPAS inertial measuring unit (IMU) and a dual frequency airborne GPS receiver. These settings were used to meet or exceed the following accuracy specification in flat areas with minimal vegetation. 24.5cm ACCz, 95% (12.5cm RMSEz) 29.4cm ACCz, 95% (15.0cm RMSEz) 29.4cm ACCz 95% (15.0cm RMSEz).

2. Specifications for the Dakota Block (2 points/square meter):

The settings for the FLI-MAP sensor included acquisition at 2,700' AMT, 145 knots, 30% sidelap, 150kHz, 60% degree field of View, 3,116ft swath to attain an approximate 8 points per square meter. This sensor was also equipped with an inertial measuring unit (IMU) and a dual frequency airborne GPS receiver. These settings were used to meet or exceed the following accuracy specification in flat areas with minimal vegetation. 17.64cm ACCz 95% (9.0cm RMSEz) 24.5cm ACCz 95% (12.5cm RMSEz) 24.5cm ACCz 95% (12.5cm RMSEz).

3. Specifications for the Metro Block and the Maple Grove Block (8 points/square meter):

The settings for the FLI-MAP sensor included acquisition at 2,100' AMT, 130 knots, 60% sidelap, 200kHz, 60% degree field of View, 2,424ft swath to attain an approximate 8 points per square meter. This sensor was also equipped with an inertial measuring unit (IMU) and a dual frequency airborne GPS receiver. These settings were used to meet or exceed the following accuracy specification in flat areas with minimal vegetation 17.64cm ACCz 95% (9.0cm RMSEz) 24.5cm ACCz 95% (12.5cm RMSEz) 24.5cm ACCz 95% (12.5cm RMSEz).


The data set for each flight line was checked for project area coverage, data gaps between overlapping flight lines, and tension/compression areas (areas where data points are more or less dense that the average project specified post spacing). Using an iterative process that involves analyzing raster difference calculations the omega, phi, kappa angle corrections for the LiDAR instrument were determined. Corrections were applied to the LiDAR data set. Extensive comparisons were made of vertical and horizontal positional differences between points common to two or more LiDAR flight lines. An intensity raster for each flight line was generated and verified that intensity was recorded for each LiDAR point. LiDAR ground points were compared to independently surveyed and positioned ground control points in the project area. Based on the results of these comparisons, the LiDAR data was vertically biased to the ground.

PRE-PROCESSING STAGE LiDAR, GPS and IMU data are processed together using LiDAR processing software. The LiDAR data set for each flight line is checked for project area coverage and LiDAR post spacing is checked to ensure it meets project specifications. The LiDAR collected at the calibration area is used to correct the rotational, atmospheric, and vertical elevation differences that are inherent to LiDAR data. Intensity raster is generated to verify that intensity was recorded for each LiDAR point. LiDAR data is transformed to the specified project coordinate system. By utilizing the ground survey data collected at the calibration site and project area, the LiDAR data is vertically biased to the ground. Comparisons between the biased LiDAR data and ground survey data within the project area are evaluated and a final RMSE value is generated to ensure the data meets project specifications.

VENDOR DELIVERABLES

Deliverables for the LiDAR are in UTM15N NAD83 (HARN), NAVD88 Geiod09, meters.

Each geodatabase is named for its respective USGS quarter-quarter quad name; there is a tiling scheme feature class in the elevation_data file geodatabase.

Every geodatabase contains a feature dataset called "terrain_data". The terrain_data feature dataset contains up to two feature classes: Bare_Earth_Points and Hydro_Breaklines (when applicable). The Bare-Earth_Points feature class is comprised of MultipointZ shapefiles extracted from the Ground and KeyPoint LAS files. Both the Bare_Earth_Points and Hydro-Breaklines have been clipped to the USGS quarter-quarter quad extent.

Each geodatabase also contains a DEM. The DEM was created from a terrain using bare-earth multipoint PointZ and hydro-breaklines. The Terrain was then converted to a Raster DEM using a 1-meter cell-size, then clipped to an adjusted, quarter-quarter quad minimum-bounding rectangle and buffered an additional 50 meters. The naming convention for all DEMs is "DEM01".

LAS files are clipped to the provided USGS quarter-quarter quad. For the higher density blocks (Dakota Block; Metro Block; Maple Grove Block), the vendor tiled the las files further, breaking each standard tile into 16 additional tiles. They are simply appended an A,B,C, or D starting in the upper left and proceeding in a clockwise direction. A sample image ( www.mngeo.state.mn.us/chouse/elevation/16tile_naming_convention.jpg ) taken from the tile index map that is on the FTP site, shows a single tile with the sub-block lettering scheme. A sample tile name would be: 4243-02-30_a_a.laz

Water edges were created using proprietary processes to create an accurate 3D representation of water features. Further hands-on evaluations are performed to ensure compliance with USGS V13 regarding Hydro-Flattening. Once the waterbodies are finalized, LAS bare-earth points within the extents of the water polygons are classified to Class 9 (Water). Bare-earth points within 1-meter of the water polygons are re-classified to Class 10 (Ignored Class).


ADDITIONAL PRODUCTS GENERATED BY MINNESOTA DNR STAFF:

These products 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 1. LAS data were classified using the following standard ASPRS categories:

1 Unclassified
2 Ground (Bare Earth)
3 Low Vegetation (less than 1.1 meters)
4 Medium Vegetation (1.11 - 2.4 meters)
5 High Vegetation (2.41 - 200m)
6 Buildings
7 Noise
8 Model Keypoint
9 Water
10 Water Edge (withheld / ignored ground) (Bare-earth points within 1-meter of the water polygons are re-classified to Class 10)
11 Scan Edge (unreliable points near the extreme edge of swath)
12 Overlap (not used)
14 Bridge Decks


2. Contours

Elevation: Integer value of elevation at contour
Contour_type:
- Index (10-foot contours)
- Index Depression
- Intermediate
- Depression


3. Edge of Water Breaklines Type

- Island: Island in a lake feature greater than 2 acres
- Island Stream: Island in a stream feature greater than 2 acres
- Lake: Lake feature greater than 2 acres
- Stream: Riverine feature greater than 100 feet wide
Detailed Citation
Table Detail:

Section 6 Distribution
Publisher Minnesota Department of Natural Resources
Publication Date 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 Twin Cities Metro LiDAR 2011
Distribution Liability 1. The 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 (or click the link below in the Online Linkage field)

- 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/
The county mosaics are named elevation_data.gdb.zip For details of their 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/

c. In folders divided by block at: ftp.lmic.state.mn.us/pub/data/elevation/lidar/projects/metro/
The boundaries for the blocks are shown on this map: lidar.dnr.state.mn.us/documentation/status/metro_data_delivery_dates.pdf


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 04/28/2014
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: 04/28/2014
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