2017 USGS Lidar: La Salle 4 County, IL

Product: These lidar data are processed Classified LAS 1.4 files, formatted to individual 2000 foot x 2000 foot tiles; used to create intensity images, 3D breaklines and hydro-flattened DEMs as necessary.

Geographic Extent:

USGS_LPC_IL_LaSalle_B1 -

LaSalle County, Illinois, covering approximately 1,148 square miles. LaSalle County is one area of interest (AOI) from a lidar survey that was collected over two (2) areas of interest in Illinois identified as LaSalle and Expansion Counties.

USGS_LPC_IL_LaSalle_B2 -

Grundy, Kendall, and DeKalb County, Illinois (Expansion Counties), covering approximately 1,388 square miles. Grundy, Kendall, and DeKalb Counties are one area of interest (AOI) from a lidar survey that was collected over two (2) areas of interest in Illinois identified as LaSalle and Expansion Counties.

LaSalle County and the Expansion Counties cover a total of approximately 2,563 square miles.

Dataset Description:

LaSalle county, Illinois 2017 Lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.5 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.2; Quality Level 2+. The data was developed based on a horizontal projection/datum of NAD83 (2011), State Plane Coordinate System Illinois East (FIPS 1201), US Survey Feet and vertical datum of NAVD88 (GEOID12B), US Survey Feet. Lidar data was delivered as flightline-extent unclassified LAS swaths, as processed Classified LAS 1.4 files, formatted to 8241 individual 2000 foot x 2000 foot tiles, as tiled Intensity Imagery, and as tiled bare earth DEMs; all tiled to the same 2000 foot x 2000 foot schema.

Grundy, Kendall, and DeKalb Counties, Illinois 2017 Lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.7 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.2; Quality Level 2. The data was developed based on a horizontal projection/datum of NAD83 (2011), State Plane Coordinate System Illinois East (FIPS 1201), US Survey Feet and vertical datum of NAVD88 (GEOID12B), US Survey Feet. Lidar data was delivered as flightline-extent unclassified LAS swaths, as processed Classified LAS 1.4 files, formatted to 10097 individual 2000 foot x 2000 foot tiles, as tiled Intensity Imagery, and as tiled bare earth DEMs; all tiled to the same 2000 foot x 2000 foot schema.

Ground Conditions:

Lidar was collected in November 2017. Due to an isolated anomaly found in the the lidar data in LaSalle County one re-flight was flown in April 2018, while no snow was on the ground and rivers were at or below normal levels. A Low Confidence polygon was use to circumscribe an area where lidar was reflected by particulates in smoke stack emission. Photons were unable to penetrate through the emissions for collection of ground surface within the polygon. The emission cloud obscures approximately 3.72 acres of ground surface. Tiles in which the emission cloud occurred are 99101727 and 99301727. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, GRW Aerial Surveys, Inc. established a total of 53 ground control points of which 50 were used to calibrate the lidar to known ground locations established throughout the LaSalle and Expansion Counties project areas. An additional 157 independent accuracy checkpoints, 89 in Bare Earth and Urban landcovers (89 NVA points), 68 in tall Grass/tall weeds/crops, Brush lands/short trees, Forested categories (68 VVA points), were used to assess the vertical accuracy of the data of the entire project area. These checkpoints were not used to calibrate or post process the data.

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the Entwine Point Tiles (EPT) hosted by USGS on Amazon Web Services.

To acquire QL2+ lidar detailing surface elevation data, vegetation, and building rooftops for use to support the 3DEP mission, the FEMA Risk MAP program, NRCS agricultural conservation practice planning in support of the Illinois Nutrient Loss Reduction Strategy and the Mississippi River Basin Initiative, NPS studies of the Illinois and Michigan Canal National Heritage Corridor and USACE hydrologic studies of the Fox River Basin. Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create Intensity Images, Breaklines, and Raster DEM. The purpose of these lidar data was to produce high accuracy 3D hydro-flattened Digital Elevation Model (DEM) with a 2 US survey feet cell size. These lidar point cloud data were used to create intensity images, 3D breaklines, and hydro-flattened DEMs as necessary.

USGS Contract No. G17PD00317 CONTRACTOR: Aerial Services, Inc. Lidar data was acquired and calibrated by the prime contractor. SUBCONTRACTOR: GRW Aerial Surveys, Inc. preformed hydro collection for northern 2/3 section of LaSalle 2+ project area from bare earth surface supplied by prime. GRW Aerial Surveys, Inc. then undertook manual building cleanup for the central 1/3 of the project from classified LAS supplied by prime. SUBCONTRACTOR: Survey And Mapping, LLC (SAM) manually edited bare earth surface, preformed hydro collection, flattening, and produced bare earth DEMs for the southcentral 1/3 of the project area. All follow-on manual editing and processing was completed by the prime contractor.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "USGS-NGP Base Lidar Specification v1.2",

"ldrsens" : "Leica ALS70-HP Airborne LiDAR Scanner",

"ldrmaxnr" : "4",

"ldrnps" : "0.5",

"ldrdens" : "4",

"ldranps" : "0.5",

"ldradens" : "4",

"ldrfltht" : "1100",

"ldrfltsp" : "150",

"ldrscana" : "50",

"ldrscanr" : "47",

"ldrpulsr" : "240",

"ldrpulsd" : "4",

"ldrpulsw" : "0.25",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.22",

"ldrswatw" : "1025",

"ldrswato" : "30",

"ldrgeoid" : "National Geodetic Survey (NGS) Geoid12B"

},

"ldraccur" : {

"ldrchacc" : "0.12",

"rawnva" : "0.094",

"rawnvan" : "89",

"clsnva" : "0.103",

"clsnvan" : "89",

"clsvva" : "0.272",

"clsvvan" : "68"

},

"lasinfo" : {

"lasver" : "1.4",

"lasprf" : "6",

"laswheld" : "Withheld (ignore) points were identified in these files using the standard LAS Withheld bit.",

"lasolap" : "Swath "overage" points were identified in these files using the standard LAS overlap bit",

"lasintr" : "16",

"lasclass" : {

"clascode" : "1",

"clasitem" : "Processed, but Unclassified"

},

"lasclass" : {

"clascode" : "2",

"clasitem" : "Bare Earth Ground"

},

"lasclass" : {

"clascode" : "3",

"clasitem" : "Low Vegetation"

},

"lasclass" : {

"clascode" : "4",

"clasitem" : "Medium Vegetation"

},

"lasclass" : {

"clascode" : "5",

"clasitem" : "High Vegetation"

},

"lasclass" : {

"clascode" : "6",

"clasitem" : "Building"

},

"lasclass" : {

"clascode" : "7",

"clasitem" : "Low Noise"

},

"lasclass" : {

"clascode" : "9",

"clasitem" : "Water"

},

"lasclass" : {

"clascode" : "10",

"clasitem" : "Ignored Ground"

},

"lasclass" : {

"clascode" : "17",

"clasitem" : "Bridge Decks"

},

"lasclass" : {

"clascode" : "18",

"clasitem" : "High Noise"

}

}}

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management or its partners.

Data is available online for bulk and custom downloads.

None

Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations. Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data.

Eighteen checkpoints were determined to be photo-identifiable in the intensity imagery and were used to test the horizontal accuracy of the LiDAR dataset. As only eighteen (18) checkpoints were photo-identifiable, the results are not statistically significant enough to report as a final tested value, but the results of the testing are still shown in the table below. Using NSSDA methodology (endorsed by the ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014)), horizontal accuracy at the 95% confidence level (called ACCURACYr) is computed by the formula RMSEr * 1.7308 or RMSExy * 2.448. No horizontal accuracy requirements or thresholds were provided for this project. However, LiDAR datasets are generally calibrated by methods designed to ensure a horizontal accuracy of 1 meter or less.

Actual positional accuracy of this dataset was found to be RMSEx = 0.129 ft (3.931 cm) and RMSEy = 0.183 (5.578 cm) which equates to +/- 0.658 ft (20.056 cm) at 95% confidence level.

For the vertical accuracy assessment of IL_LaSalle and Expansion Counties project, one hundred fifty seven check points were surveyed. Eighty nine of those check points are located within bare earth/open terrain (89 NVA points). Sixty eight check points are located within grass/weeds/crops, brush/low trees, and forested/fully grown land cover categories (68 VVA points). Checkpoints were evenly distributed throughout the project area so as to cover as many flight lines as possible using the dispersed method of placement. These checkpoints were not used to calibrate or post process the data.

For the IL_LaSalle QL2+ and Expansion Counties QL2 project, the tested RMSEz of the classified LiDAR data for checkpoints in non-vegetated terrain equaled 5.26 cm (0.173 ft), compared with the 10 cm (0.33 ft) specification: and the NVA of the classified LiDAR data computed using RMSEz x 1.96 was equal to 10.31 cm (0.338 ft), compared with the 19.6 cm (0.64 ft) specification. For the IL_LaSalle QL2+ and Expansion Counties project, the tested VVA of the classified LiDAR data computed using the 95th percentile was equal to 27.21 cm (0.893 ft), compared with the 29.4 cm (0.96 ft) specification.

These LAS data files include all data points collected. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The raw point cloud is of good quality and data passes Non-Vegetated Vertical Accuracy specifications.

Data covers the entire area specified for this project.

Data is backed up to tape and to cloud storage.

The NOAA Office for Coastal Management (OCM) ingested references to the USGS Entwine Point Tile (EPT) files hosted on Amazon Web Services (AWS) into the Digital Coast Data Access Viewer (DAV). The DAV accesses the point cloud as it resides on AWS under the usgs-lidar-public-container.