| Section 1 | Overview | |||
| Originator | Merrick & Company | |||
| Title | LiDAR Elevation, Wright County, Minnesota, 2008 | |||
| Abstract | The LiDAR data for Wright County was collected under contract by the county. Thus, the data format is not entirely consistent with some of the other LiDAR data collected for the State of Minnesota. Specifically, the Wright 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 Wright 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. Note: This metadata record was created at the Minnesota Geospatial Information Office by combining information supplied by Merrick, Wright County, and the Minnesota Department of Natural Resources. | |||
| Purpose | ||||
| Time Period of Content Date | 2008 | |||
| Currentness Reference | April 23 - May 28, 2008 | |||
| Progress | Complete | |||
| Maintenance and Update Frequency | Unknown | |||
| Spatial Extent of Data | Wright County, Minnesota | |||
| Bounding Coordinates | -93.512431 -93.491196 45.270467 45.255847 | |||
| Place Keywords | Wright 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 | See Disclaimer field for complete use conditions. | |||
| Contact Person Information | Steven A. Jobe,
Wright County Surveyor Wright County 1901 Hwy 25 North Buffalo, MN 55313 Phone: 763-682-7690 Fax: 763-682-7313 Email: steve.jobe@co.wright.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 | 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. 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 | The contour coverage is checked for arc and node topology. These checks include verifying that no dangling nodes exist, and that no unnecessary pseudo nodes exist, which will result in the minimum number of arcs present in a coverage. The coverage is then exported to an ESRI shapefile. | |||
| Completeness | Contours that are less than 25 feet in length, and that share the same from and to 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's Processing Steps:
Contours: LiDAR data was collected using Merrick's ALS50 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 shapefiles. The contour data was checked for spikes and holes, and then imported into an Arc/Info coverage for building topology and coding contour types. The coverage was then exported to an ESRI shapefile for delivery. Breaklines: The breaklines were captured using Microstation v8. The resulting .dgn file was brought into ArcScene and exported to a 3d polyline shapefile (x, y, and z attributes). The deliverables from Merrick to Wright County were: Digital orthos in TIFF and MrSID formats; DSM (LiDAR first return) in ASCII, binary LAS, and ESRI grid formats; DEM (LiDAR bare-earth) in ASCII, binary LAS, and ESRI grid formats; DTM (LiDAR bare-earth with breaklines) in ASCII, CSV (comma de-limited), binary LAS, and ESRI grid formats; Breaklines in 3D shapefile and DXF formats; 2-foot Contours in 3D shapefile and DXF formats; Spot elevations in 3D shapefile and DXF formats. All deliveries were in the Wright County (MN) Coordinate System, North American Datum of 1983 (NAD 83), NSRS 2007 adjustment, U.S. Survey foot. The vertical datum was NAVD 88. Minnesota Department of Natural Resources Processing Steps 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 DEMS are hydro-flattened and enforced using the breakline features. All processing was done in December 2011 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 | Minnesota DNR | |||
| Publication Date | ||||
| Contact Person Information | Nancy Rader,
GIS Data Coordinator Minnesota Geospatial Information Office 658 Cedar Street St. Paul, MN 55155 Phone: 651-201-2489 Email: clearing.house@state.mn.us | |||
| Distributor's Data Set Identifier | Wright LiDAR 2008 | |||
| Distribution Liability | 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.
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 | 02/26/2013 | |||
| Contact Person Information | Nancy Rader,
GIS Data Coordinator Minnesota Geospatial Information Office 658 Cedar Street St. Paul, MN 55155 Phone: 651-201-2489 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 | |||