LiDAR Elevation, Central Lakes Region, Minnesota, 2012

This page last updated: 11/04/2013
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 Minnesota Department of Natural Resources and Woolpert, Inc.
Title LiDAR Elevation, Central Lakes Region, Minnesota, 2012
Abstract The project vendor, Woolpert, Inc., acquired highly accurate Light Detection and Ranging (LiDAR) elevation data for the Central Lakes area of Minnesota in Spring 2012. The data cover Aitkin, Cass, Hubbard, Itasca, Todd and Wadena counties, along with a portion of Koochiching County. LiDAR data are in the UTM Zone 15 coordinate system, NAD83 96, 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 then quality checked the data and created two additional products: two-foot contours and building outlines.

This metadata record was created at the Minnesota Geospatial Information Office using information supplied by Woolpert 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 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 2012
Currentness Reference 2012 flight dates: April 5-6, 10-12, 14, 19, 20, 23-24, 26-28
Progress Complete
Maintenance and Update Frequency Unknown
Spatial Extent of Data Central Lakes region, Minnesota
Bounding Coordinates -95.312416
-93.000201
48.687949
45.709332
Place Keywords Minnesota, Aitkin, Cass, Hubbard, Itasca, Todd, Wadena, Koochiching
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 The LiDAR collected for this task order was tested to meet a vertical accuracy of 5.0 cm (0.16 ft) Root Mean Squared Error (RMSE).
Logical Consistency All formatted data are validated using commercial GIS software to ensure proper formatting and loading prior to delivery.
Completeness The LIDAR data is visually inspected for completeness to ensure that are no gaps between flight lines.
Horizontal Positional Accuracy The NAD83 96 datum was used.

Compiled to meet +/- 3.8ft horizontal accuracy at 95 percent confidence level.
Vertical Positional Accuracy 1. Woolpert: The LiDAR data vertical accuracy RMSE is 5.0 cm (0.16 ft). The data collected under this Task Order meets the National Standard for Spatial Database Accuracy (NSSDA) accuracy standards. The NSSDA standards specify that vertical accuracy be reported at the 95 percent confidence level for data tested by an independent source of higher accuracy. ( www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part3/index_html ).Tested 9.8cm (0.31ft) fundamental vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using (RMSE) x 1.96000 Tested against the TIN using independent check points.

2. Report from DNR: The LiDAR collected for this task order was tested using independent, locally provided validation points.

The vertical accuracy (Z-RMSE):
Block 1: 15.4 cm.
Block 2: 13.7 cm.
Block 3: 12.0 cm.
Block 4: 18.6 cm.
Block 5: 11.1 cm.

See detailed reports in each block folder, for example, for Block 1: ftp.lmic.state.mn.us/pub/data/elevation/lidar/projects/central_lakes/block_1/Central_Lakes_block_1_validation_report.pdf
Lineage Vendor Processing Steps:

Using Light Detection And Ranging (LiDAR) systems, 442 flight lines of high density data, at a nominal pulse spacing (NPS) of 1.5 meter, were collected over Minnesota counties of Aitkin, Cass, Hubbard, Itasca, Todd, Wadena and a portion of Koochiching (approximately 11,690 sq. miles), along with a 100 meter buffer beyond the project tile boundary. Multiple returns were recorded for each laser pulse along with an intensity value for each return. A total of thirty one (31) missions were flown from April 05, 2012 through April 28, 2012. A minimum of six (6) airborne global positioning system (GPS) base stations were used in support of the LiDAR data acquisition. All data for this task order is referenced to UTM 15N, NAD83, NAVD88, in meters. Airborne GPS data was differentially processed and integrated with the post processed IMU data to derive a smoothed best estimate of trajectory (SBET). The SBET was used to reduce the LiDAR slant range measurements to a raw reflective surface for each flight line. The coverage was classified to extract a bare earth digital elevation model (DEM) and separate last returns. In addition to the LAS deliverables, one layer of coverage was delivered in the ArcGrid binary format: bare-earth.
System Parameters for 1.5 NPs:

ALS60 Specifications
Post Spacing (Minimum): 4.92 ft / 1.5 m
AGL (Above Ground Level) average flying height: 7,800 ft / 2,377.4 m
MSL (Mean Sea Level) average flying height: 9,000 ft / 2712.7 m
Average Ground Speed: 150 knots / 172.6 mph
Field of View (full): 40 degrees
Pulse Rate: 99 kHz
Scan Rate: 38 Hz
Side Lap (Minimum): 25%

ALS70 Specifications
Post Spacing (Minimum): 4.92 ft / 1.5 m
AGL (Above Ground Level) average flying height: 7,800 ft / 2,377.4 m
MSL (Mean Sea Level) average flying height: 9,075 ft / 2766 m
Average Ground Speed: 150 knots / 172.6 mph
Field of View (full): 40 degrees
Pulse Rate: 115.3 kHz
Scan Rate: 25.1 Hz
Side Lap (Minimum): 25%

Optech ALTM Gemini Specifications
Post Spacing (Minimum): 4.92 ft / 1.5 m
AGL (Above Ground Level) average flying height: 6,800 ft / 2,072.6 m
MSL (Mean Sea Level) average flying height: 9,000 ft / 2712.7 m
Average Ground Speed: 150 knots / 172.6 mph
Field of View (full): 40 degrees
Pulse Rate: 99.1 kHz
Scan Rate: 38 Hz
Side Lap (Minimum): 25%

The ALS60, ALS70 and Optech Gemini calibration and system performance is verified on a periodic basis using Woolpert's calibration range. The calibration range consists of a large building and runway. The edges of the building and control points along the runway have been located using conventional survey methods. Inertial measurement unit (IMU) misalignment angles and horizontal accuracy are calculated by comparing the position of the building edges between opposing flight lines. The scanner scale factor and vertical accuracy is calculated through comparison of LiDAR data against control points along the runway. Field calibration is performed on all flight lines to refine the IMU misalignment angles. IMU misalignment angles are calculated from the relative displacement of features within the overlap region of adjacent (and opposing) flight lines. The raw LiDAR data is reduced using the refined misalignment angles.

Once the data acquisition and GPS processing phases are complete, the LiDAR data was processed immediately to verify the coverage had no voids. The GPS and IMU data was post processed using differential and Kalman filter algorithms to derive a best estimate of trajectory. The quality of the solution was verified to be consistent with the accuracy requirements of the project.

The individual flight lines were inspected to ensure the systematic and residual errors have been identified and removed. Then, the flight lines were compared to adjacent flight lines for any mismatches to obtain a homogenous coverage throughout the project area. The point cloud underwent a classification process to determine bare-earth points and non-ground points utilizing "first and only" as well as "last of many" LiDAR returns. This process determined The LiDAR LAS files for this task order have been classified into the Default (Class 1), Ground (Class 2), Low Vegetation (Class 3), Medium Vegetation (Class 4), High Vegetation (Class 5) Buildings (Class 6), Noise (Class 7), Model Keypoints (Class 8), Water (Class 9), Ignored Ground (Class 10), bridges (Class 14), and Overlap (Class 17) classifications. The bare-earth (Class 2 - Ground) LiDAR points underwent a manual QA/QC step to verify that artifacts have been removed from the bare-earth surface. The surveyed ground control points are used to perform the accuracy checks and statistical analysis of the LiDAR dataset.

Breaklines defining lakes, greater than two acres, and double-line streams, wider than 30.5 meters (100 feet), were compiled using digital photogrammetric techniques as part of the hydrographic flattening process and provided as ESRI Polygon Z shape files. Breaklines defining water bodies and streams were compiled for this task order. The breaklines were used to perform the hydrologic flattening of water bodies, and gradient hydrologic flattening of double line streams. Lakes, islands, reservoirs and ponds, at a nominal minimum size of two (2) acres or greater, were compiled as closed polygons. The closed water bodies were collected at a constant elevation. Rivers and streams, at a nominal minimum width of 30.5 meters (100 feet), were compiled in the direction of flow with both sides of the stream maintaining an equal gradient elevation.

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:

0 Unclassified
1 Unknown
2 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
14 Bridge Decks
17 Overlap


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 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: clearing.house@state.mn.us
Distributor's Data Set Identifier Central Lakes LiDAR 2012
Distribution Liability 1. Woolpert prepared the original data as set forth in the Scope of Services, in accordance with reasonable care and due diligence as set forth in this Agreement, however, due to the easily alterable nature of electronic media, files, documents, and other deliverables, Woolpert, Inc. makes no warranties, either expressed or implied, with respect to the accuracy, completeness, merchantability, or fitness for any particular purpose, including, but not limited to, use of any/all data as described within this metadata file, by any user of this data. Any use will be at the end-user's sole risk.

2. The Minnesota Department of Natural Resources General Geographic Data License Agreement is online: www.dnr.state.mn.us/sitetools/data_software_license.html

3. MnGeo's data disclaimer is online: www.mngeo.state.mn.us/chouse/disclaimer.html
Ordering Instructions The LiDAR data provided by DNR may be downloaded from MnGeo's FTP site by clicking on the link below, where the data is arranged in folders by county (aitkin, cass, hubbard, itasca, todd and wadena).

Alternatively:
- The data is also provided in folders divided by block at: ftp.lmic.state.mn.us/pub/data/elevation/lidar/projects/central_lakes/ The boundaries for the blocks are shown on this map:
www.mngeo.state.mn.us/chouse/elevation/Central_Lakes_Delivery_Schedule.pdf

- The tiles are provided at:
ftp.lmic.state.mn.us/pub/data/elevation/lidar/q250k/
Use the tile_index.pdf maps to locate the tiles you need.

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 11/04/2013
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: clearing.house@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: 11/04/2013
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