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LiDAR Elevation Data: St. Croix County, WI 2021

Identification Information

Citation
Title
LiDAR Elevation Data: St. Croix County, WI 2021
Originator
U.S. Geological Survey
Creation Date
2021-03-28
Publication Date
2021-03-28
Edition
2021
Geospatial Data Presentation Form
mapDigital
Other Citation Details
Contract No. G16PC00016, Task Order No. 140G0221F0085; CONTRACTOR: NV5 Geospatial
Abstract
This data represents LiDAR elevation information for St. Croix County, Wisconsin in 2021. The following derivative products are available: classified LAS, hydro breaklines, tiled DEMs, tiled intensity images, and a tile index file. Also included are several countywide products created by the WisconsinView Partners - the WI Department of Administration’s Geographic Information Office in collaboration with the UW-Madison Space Science and Engineering Center’s (SSEC) WisconsinView repository. Original lidar data in tiled format from federal (USGS 3DEP) and/or local county lidar projects were used to create countywide mosaics of specific datasets such as DEMS, Intensity values and DSMs in various projections and coordinate systems. [These lidar data are processed Classified LAS 1.4 files, formatted to 1070 individual 4500 ft x 4500 ft tiles; used to create intensity images, 3D breaklines, and hydro-flattened DEMs as necessary. Geographic Extent: 6 counties in Wisconsin, covering approximately 742 total square miles. Dataset Description: The 37876_WI_Statewide_2021_B21 project, Work Unit 300036 called for the planning, acquisition, processing, and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.71 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LiDAR Specification, 2020 rev. A. The data were developed based on a horizontal projection/datum of NAD 1983 2011 WISCRS St Croix Feet, Foot US and vertical datum of NAVD88 Geoid 18, Foot US. LiDAR data were delivered as processed Classified LAS 1.4 files formatted to 1070 individual 4500 ft x 4500 ft tiles, as tiled intensity imagery, and as tiled bare earth DEMs; all tiled to the same 4500 ft x 4500 ft schema. Continuous breaklines were produced in Esri file geodatabase format. Ground Conditions: LiDAR was collected in spring 2021, while no snow was on the ground and rivers were at or below normal levels. These are Digital Elevation Model (DEM) data for Wisconsin as part of the required deliverables for the 37876_WI_Statewide_2021_B21 project. Class 2 (ground) LiDAR points in conjunction with the hydro breaklines were used to create a 2 foot hydro-flattened Raster DEM.]
Purpose
To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments and elevation modeling, etc. Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create intensity images, breaklines and raster DEMs. The purpose of these LiDAR data was to produce high accuracy 3D hydro-flattened digital elevation models (DEMs) with a 2 foot cell size. These raw LiDAR point cloud data were used to create classified LiDAR LAS files, intensity images, 3D breaklines, and hydro-flattened DEMs as necessary.
Supplemental Information
Data is available for download from: https://web.s3.wisc.edu/wsco-wisconsinview/lidar/St_Croix/St_Croix_2021_3DEP_Delivery/ Detailed, original metadata accompanying this LiDAR data is available: https://web.s3.wisc.edu/wsco-wisconsinview/lidar/St_Croix/St_Croix_2021_3DEP_Delivery/Metadata/ DEM: Raster File Type = GeoTIFF; Bit Depth/Pixel Type = 32-bit float; Raster Cell Size = 2 foot; Interpolation or Resampling Technique = Triangulated Irregular Network (TIN), Linear Interpolation, Proprietary; Required Vertical Accuracy = 0.196
Temporal Extent
Time Instant
2021-03-28T00:00:00
Bounding Box
West
-92.8049621432
East
-92.1316307414
North
45.2113746105
South
44.856490581
ISO Topic Category
elevation
Place Keyword
St. Croix County
Wisconsin
Place Keyword Thesaurus
GNS
Theme Keyword
Digital elevation models
Theme Keyword Thesaurus
LCSH
Theme Keyword
Lidar
Grids
Contours
Surface models
Terrain models
Relief models
Hydrography
Topography
Elevations
Theme Keyword Thesaurus
LCSH
Resource Constraints
Use Limitation
None. However, users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of their limitations. Acknowledgement of the organization providing these data to the public would be appreciated for products derived from these data.
Status
completed
Maintenance and Update Frequency
unknown
Language
eng
Credit
U.S. Geological Survey
Point of Contact
Contact
U.S. Geological Survey
Point of Contact
Contact
NV5 Geospatial
Email
jackie.monge@nv5.com
Phone
859-277-8700

Spatial Reference Information

Reference System Identifier
Code
8118
Code Space
EPSG
Version
9.7

Data Quality Information

Completeness Commission
Lineage
Process Step
Description
LAS: Raw Data and Boresight Processing: The boresight for each lift was done individually as the solution may change slightly from lift to lift. The following steps describe the Raw Data Processing and Boresight process: 1) Technicians processed the raw data to LAS format flight lines using the final GPS/IMU solution. This LAS data set was used as source data for boresight. 2) Technicians first used NV5 Geospatial proprietary and commercial software to calculate initial boresight adjustment angles based on sample areas selected in the lift. These areas cover calibration flight lines collected in the lift, cross tie, and production flight lines. These areas are well distributed in the lift coverage and cover multiple terrain types that are necessary for boresight angle calculation. The technicians then analyzed the results and made any necessary additional adjustment until it was acceptable for the selected areas. 3) Once the boresight angle calculation was completed for the selected areas, the adjusted settings were applied to all of the flight lines of the lift and checked for consistency. The technicians utilized commercial and proprietary software packages to analyze how well flight line overlaps matched for the entire lift and adjusted as necessary until the results met the project specifications. 4) Once all lifts were completed with individual boresight adjustment, the technicians checked and corrected the vertical misalignment of all flight lines and also the matching between data and ground truth. The relative accuracy was less than or equal to 7 cm RMSEz within individual swaths and less than or equal to 10 cm RMSEz or within swath overlap (between adjacent swaths). 5) The technicians ran a final vertical accuracy check of the boresighted flight lines against the surveyed checkpoints after the z correction to ensure the requirement of NVA = 19.6 cm 95% Confidence Level (Required Accuracy) was met.
Process Step
Description
LAS Point Classification: The point classification was performed as described below. The bare earth surface was manually reviewed to ensure correct classification on the Class 2 (Ground) points. After the bare-earth surface was finalized, it was then used to generate all hydro-breaklines through heads-up digitization. All ground (ASPRS Class 2) LiDAR data inside of the Lake Pond and Double Line Drain hydro-flattened breaklines were then classified to Water (ASPRS Class 9) using proprietary tools. A buffer of 3.0 foot was also used around each hydro-flattened feature to classify these ground (ASPRS Class 2) points to Ignored ground (ASPRS Class 20). All Lake Pond Island and Double Line Drain Island features were checked to ensure that the ground (ASPRS Class 2) points were reclassified to the correct classification after the automated classification was completed. Any noise that was identified either through manual review or automated routines was classified to the appropriate class ( ASPRS Class 7 and/or ASPRS Class 18) followed by flagging with the withheld bit. All data were manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler. Global Mapper was used as a final check of the bare earth dataset. GeoCue was then used to create the deliverable industry-standard LAS files for both the Point Cloud Data and the Bare Earth. NV5 Geospatial proprietary software was used to perform final statistical analysis of the classes in the LAS files, on a per tile level to verify final classification metrics and full LAS header information.
Process Step
Description
Hydro-Flattened Raster DEM Processing: Class 2 (Ground) LiDAR points in conjunction with the hydro-breaklines were used to create a 2 foot hydro-flattened raster DEM. Using automated scripting routines in proprietary software, GeoTIFF files were created for each tile. Each surface was reviewed using Global Mapper to check for any surface anomalies or incorrect elevations found within the surface.
Process Step
Description
Add data to UW-Madison archive.
Process Date
2023-06-20T00:00:00

Distribution Information

Format Name
Various
Format Version
1.0
Distributor
University of Wisconsin-Madison
Online Access
https://web.s3.wisc.edu/wsco-wisconsinview/lidar/St_Croix/St_Croix_2021_3DEP_Delivery/
Protocol
WWW:DOWNLOAD-1.0-http--download
Name
WisconsinView.org
Function
download

Metadata Reference Information

Hierarchy Level
dataset
Metadata File Identifier
1B502236-FFA2-4624-B930-D6D052403DF7
Metadata Point of Contact
Name
Arthur H. Robinson Map Library
Position Name
metadata technician
Delivery Point
550 N. Park Street
City
Madison
Administrative Area
WI
Postal Code
53706
Country
US
Email
askmap@library.wisc.edu
Phone
(608) 262-1471
Metadata Date Stamp
2023-06-20
Metadata Standard Name
ISO 19139 Geographic Information - Metadata - Implementation Specification
Metadata Standard Version
2007
Character Set
utf8
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