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Lidar Elevation Data: Buffalo County, WI 2023

Identification Information

Citation
Title
Lidar Elevation Data: Buffalo County, WI 2023
Originator
U.S. Geological Survey
Publication Date
2024-09-11
Edition
2023
Geospatial Data Presentation Form
mapDigital
Other Citation Details
Contract No. 140G0221D0012, Task Order No. 140G0223F0161; CONTRACTOR: NV5 Geospatial
Abstract
This data represents Lidar elevation information for Buffalo County, Wisconsin in 2023. The following derivative products are available: classified LAS, hydro breaklines, a tiled DEM, intensity images, tile index file, and countywide DEMs in both WISCRS and WTM coordinate systems provided by the WisconsinView Partners. [The WI_2County_2_B23, Work Unit 300412 project called for the planning, acquisition, processing, and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.35 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LiDAR Specification, 2023 Rev. A. The data were developed based on a horizontal projection/datum of NAD83(2011) / WISCRS Buffalo (ftUS), Foot US and vertical datum of NAVD88 Geoid 18, Foot US. LiDAR data were delivered as processed Classified LAS 1.4 files formatted to 4082 individual 685 m x 685 m tiles, as tiled intensity imagery, and as tiled bare earth DEMs; all tiled to the same 685 m x 685 m schema. Continuous breaklines were produced in Esri file geodatabase format.
Purpose
This data is intended for reference and mapping purposes, and may be used for basic applications such as viewing, querying, and map output production, or to provide a basemap to support graphical overlays and analysis with other spatial data. [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 .5 meter 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
LiDAR was collected in spring 2023, while no snow was on the ground and rivers were at or below normal levels. In order to post process the LiDAR data to meet task order specifications and meet ASPRS vertical accuracy guidelines, NV5 Geospatial utilized a total of 24 ground control points that were used to calibrate the LiDAR to known ground locations established throughout the project area. An additional 159 independent accuracy checkpoints, 90 in Bare Earth and Urban landcovers (90 NVA points), 69 in Tall Weeds categories (69 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data. There are 12 empty tiles due to being over water. Breakline File Type = GDB; Breakline Elevation Units = Foot US; Downhill Treatment Applied = Monotonic, Proprietary; Type of Hydro Treatment Required = Hydro-Flattened
Temporal Extent
Time Instant
2023-05-20T00:00:00
Bounding Box
West
-92.084097
East
-91.528932
North
44.596614
South
44.028097
Bounding Box
West
-92.08705482
East
-91.5256239072
North
44.5984972905
South
44.0241802823
ISO Topic Category
elevation
Place Keyword
Buffalo County
Wisconsin
Place Keyword Thesaurus
GNS
Temporal Keyword
2023
Theme Keyword
Digital elevation models
Theme Keyword Thesaurus
LCSH
Theme Keyword
Lidar
Contours
Grids
Surface models
Terrain 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
Delivery Point
523 Wellington Way
City
Lexington
Administrative Area
Kentucky
Postal Code
40503
Country
US
Email
jackie.monge@nv5.com
Phone
(608) 443-1200

Spatial Reference Information

Reference System Identifier
Code
7533
Code Space
EPSG
Version
9.7

Data Quality Information

Completeness Commission
Completeness Commission
Lineage
Statement
Added data to UW-Madison geospatial archive in 2024.
Process Step
Description
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 is performed as described below. The bare earth surface is then manually reviewed to ensure correct classification on the Class 2 (Ground) points. After the bare-earth surface is finalized, it is 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 flattening breaklines were then classified to water (ASPRS Class 9) using TerraScan macro functionality. A buffer of 0.5 feet was also used around each hydro-flattened feature to classify these ground (ASPRS Class 2) points to Ignored ground (ASPRS Class 10). 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. All overlap data was processed through automated functionality provided by TerraScan to classify the overlapping flight line data to approved classes by USGS. The overlap data was classified using standard LAS overlap bit. These classes were created through automated processes only and were not verified for classification accuracy. Due to software limitations within TerraScan, these classes were used to trip the withheld bit within various software packages. These processes were reviewed and accepted by USGS through numerous conference calls and pilot study areas. All data was manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler. Global Mapper us 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 All Point Cloud Data and the Bare Earth. 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
Maximum Surface Height Rasters were produced as ancillary data from the classified lidar point cloud in order to evaluate the withheld bit flag proof of performance for points that cannot be reasonably interpreted as valid surface returns. These were produced using all returns, withheld flagged points excluded, and using the highest elevation point value from each pixel. These rasters are 32-bit, floating point format and delivered as GeoTIFF files per tile. MSHR are generated from the point cloud data and will not be altered after creation nor will there be further maintenance on this product.
Process Step
Description
Swath Separation Imagery was produced for the entire project area. Swath separation images use color-coding to illustrate differences in elevation (z-) values where swaths overlap. The color-coded images are semi-transparent and overlay the lidar intensity image. They are ancillary data used as visual aids to more easily identify regions within point cloud datasets that may have suspect interswath alignment or other geometric issues. Imagery was created using last returns with all classification and bit flags, except for noise and withheld bit flag are included. SSI are generated from the point cloud data and will not be altered after creation nor will there be further maintenance on this product.

Distribution Information

Format Name
Various
Format Version
1.0
Distributor
University of Wisconsin-Madison
Online Access
https://geodata.wisc.edu/
Protocol
WWW:DOWNLOAD-1.0-http--download
Name
GeoData@Wisconsin
Function
download

Spatial Representation Information

Vector
Topology Level
geometryOnly
Vector Object Type
surface
Vector Object Count

Metadata Reference Information

Hierarchy Level
dataset
Metadata File Identifier
79EE43A7-3389-4F31-B6AD-73C93254C170
Metadata Point of Contact
Name
Arthur H. Robinson Map Library
Position Name
metadata technician
Delivery Point
550 N. Park St
City
Madison
Administrative Area
Wisconsin
Postal Code
53706
Country
US
Email
askmap@library.wisc.edu
Phone
(608) 262-1471
Metadata Date Stamp
2024-09-11
Metadata Standard Name
ISO 19139 Geographic Information - Metadata - Implementation Specification
Metadata Standard Version
2007
Character Set
utf8
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