LiDAR Elevation, Crow Wing County, Minnesota, 2008

This page last updated: 04/29/2014
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 Merrick & Company
Title LiDAR Elevation, Crow Wing County, Minnesota, 2008
Abstract The LiDAR data for Crow Wing County was collected under contract by the county. Thus, the data format is not entirely consistent with some of the other LiDAR data collected by the State of Minnesota. Specifically, the Crow Wing County collect required classification of only Bare Earth in the LiDAR LAS files, so there is no information on buildings, vegetation, or model key points.

Breaklines captured as part of this effort are also a bit different. In Crow Wing County the breaklines are 3D Polyline features rather than 3D Polygon features. They also include road centerlines, stream courses and other features that are not part of the Statewide collect specifications. However, the breaklines do not have z-values associated with them so the DEMs have not been hydro-flattened.

Note: This metadata record was created at the Minnesota Geospatial Information Office by combining information supplied by Merrick & Company, Crow Wing County, and the Minnesota Department of Natural Resources.
Purpose
Time Period of Content Date 2008
Currentness Reference
Progress Complete
Maintenance and Update Frequency Unknown
Spatial Extent of Data Crow Wing County, Minnesota
Bounding Coordinates -94.396394
-93.794358
46.350879
46.153896
Place Keywords Minnesota, Crow Wing County
Theme Keywords elevation, LiDAR, DEM, digital elevation model, contour, topographic, topo, DTM, LAS, breakline
Theme Keyword Thesaurus ISO 19115
Access Constraints None
Use Constraints See Disclaimer field for complete use conditions.
Contact Person Information Doug Jacoby, Director of Projects / Project Manager
Merrick & Company
2450 South Peoria Street
Aurora, CO  80014
Phone: 303-353-3903
Fax: 303-745-0964
Email: doug.jacoby@merrick.com
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 Verification of attribute accuracy is a two-tiered QC process. The first process is based on the visual inspection of the contour data. Contours are color-coded according to type. Depressions are checked for the accuracy and consistency of coding. The second process is based on automated procedures written in Arc Macro Language (AML). The AMLs check attribute accuracy by identifying mis-matched line-types, by checking that the coding is consistent with the database design, and by verifying the data against the coverage tolerances and projection parameters.
Logical Consistency Contour coverages are checked for arc and node topology. These checks include verifying that no dangling nodes exist, and that no unsplit arcs exist, which will result in the minimum number of arcs present in a coverage. The coverages are then exported to an ESRI shapefile.
Completeness Contours that are less than 22 feet, and that share the same to and from node are not generated. Unnecessary vertices are removed using the Arc/Info Generalize command.
Horizontal Positional Accuracy Horizontal accuracy was tested by comparing the raw contours from each flightline against adjoining flightlines at specific points.
Vertical Positional Accuracy LIDAR surface was tested for vertical accuracy by comparing their values to known control points. Merrick used new and existing ground control points to support the accuracy requirements. The result of this is shown in the LIDAR control report. Supplemental breaklines were added to more accurately model certain features. Contour lines were generated from this enhanced surface and were verified for accuracy against surveyed spot elevations.
Lineage Merrick & Company Processing Steps:

LIDAR data was collected using Merrick's ALS40 sensor. The data was field-verified for complete coverage of the project area. Raw data files were parsed into manageable client-specific tiles. These tiles were then processed through automated filtering that separated the data into different classification groups: error points, ground points, and canopy-building points. The data was next taken into a graphic environment to reclassify the erroneous points that may remain in the LIDAR point cloud after auto filter. The surface was then normalized into a digital surface model (DSM). Final data extraction for the client's keypoint (statistically significant points) and canopy-building files were then generated. Using orthophotography, planimetric features were compiled as breaklines to supplement the LIDAR data. The LIDAR digital surface model was then processed with the breaklines, and contour lines were interpolated. The contours were exported from Merrick's MARS software into ESRI shape files. The contour data was checked for spikes and holes, and then imported into Arc/Info coverages for building topology, coding contour types, and creating annotation. The coverage was exported to an ESRI shapefile for delivery.

Minnesota Department of Natural Resources Processing Steps:

This acquisition of this data was coordinated by staff at Crow Wing County. The data has been projected from Crow Wing county coordinates to UTM Zone 15, NAD83 Datum and the elevation units have been scaled from feet to meters. The LAS files were then retiled to the 1/16 of a USGS 1:24,000 scale quadrangle. All of this work was done using LP360 tools.
The points in the LAS files were then sorted on GPS_TIME to put points collected next to each other in time (and thus space) close to each other in the file to speed access and increase compression efficiency. The files were then assigned a UTM Zone 15, NAD83 projection header and compressed to LAZ format using LASZIP.
The LAS files found here deviate from the State Standard when it comes to classification. What you will find are bare earth points and other points. While all points are there, those that are not bare earth are not classified. The two classes that exist are 1 - Unclassified and 2 - Ground.

DEM data provided by Crow Wing County was not hydrologically conditioned or hydro flattened even though breaklines were provided. So, the DEMs were recreated using the following technique
a) Created a terrain feature dataset
b) Added bare earth points and breaklines to the terrain feature dataset
c) Established pyramid levels
d) Build Terrain
e) Exported a 1-meter DEM from the Terrain
f) Created a hillshade from the 1-meter DEM
g) Created a 3-meter DEM from the one meter DEM
h) Created a 3-meter hillshade

Summary of procedures:

1) LAS files were projected from County Coordinates to UTM Zone 15, NAD83
2) LAS point Z values were scaled from feet to meters
3) LAS files were retiled into the state tile scheme (1/16 of a USGS 1:24,000 scale quadrangle)
4) Breakline features were merged together into a single feature class
5) Breakline features were projected from County Coordinates to UTM Zone 15, NAD83
6) Breakline Z Values were scaled from feet to meters
7) LAS Bare Earth Points and breaklines were used to create a Terrain data type
8) 1-meter DEM was derived from Terrain using nearest neighbor interpolation option (DEM01)
9) Hillshade was derived from 1-meter DEM (DEM01HS)
10) 3-meter DEM was derived from Terrain using nearest neighbor interpolation option (DEM03)
11) Hillshade was derived from 3-meter DEM (DEM03HS)
12) Aspect was derived from 3-meter DEM (DEM03ASPECT)
13) Slope in degrees was derived from 3-meter DEM (DEM03SLOPE_DEGREES)
14) Slope in percent was derived from 3-meter DEM (DEM03SLOPE_PERCENT)
15) DEM03 was smoothed using a 3x3 mean smoothing filter
16) 2-foot contours were created from the smoothed 3-meter DEM

All processing was done using ArcGIS V10 and LP360 Extensions

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 Contour types (ftype attribute): Index, Index Annotation, Index Depression, Index Depression Obscured, Index Hidden, Index Obscured, Intermediate, Intermediate Depression, Intermediate Depression Obscured, Intermediate Hidden, Intermediate Obscured
Detailed Citation
Table Detail:

Section 6 Distribution
Publisher
Publication Date 02/05/2008
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 Crow Wing County LiDAR
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/crowwing/
The county mosaic is named elevation_data.gdb.zip 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 04/29/2014
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: 04/29/2014
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