2017 USGS Lidar: Northeast IL 4 County (Cook, Kane, Lake, McHenry)

Product: These lidar data are processed Classified LAS 1.4 files, formatted to 14,829 individual 2500 ft x 2500 ft tiles; used to create Reflectance Images, 3D breaklines and hydro-flattened DEMs as necessary.

Geographic Extent: Cook, Kane, Lake, and McHenry counties, Illinois

Dataset Description: The WI Kenosha-Racine Counties and IL 4 County QL1 Lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a derived nominal pulse spacing (NPS) of 1 point every 0.35 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.2. The data was developed based on a horizontal projection/datum of NAD83 (2011), State Plane, U.S Survey Feet and vertical datum of NAVD88 (GEOID12B), U.S. Survey Feet. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 14,829 individual 2500 ft x 2500 ft tiles, as tiled Reflectance Imagery, and as tiled bare earth DEMs; all tiled to the same 2500 ft x 2500 ft schema.

Ground Conditions: Lidar was collected April-May 2017, 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, Ayers established a total of 66 ground control points that were used to calibrate the lidar to known ground locations established throughout the WI Kenosha-Racine Counties and IL 4 County QL1 project area. An additional 195 independent accuracy checkpoints, 116 in Bare Earth and Urban landcovers (116 NVA points), 79 in Tall Grass and Brushland/Low Trees categories (79 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

The NOAA Office for Coastal Management (OCM) downloaded this data set from this USGS site:

ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/

The datasets downloaded were:

USGS_LPC_IL_4County_Cook_2017_LAS_2019/ Number of files: 5527

USGS_LPC_IL_4County_Kane_2018_LAS_2019/ Number of files: 3644

USGS_LPC_IL_4County_Lake_2016_LAS_2019/ Number of files: 2117

USGS_LPC_IL_4County_McHenry_2018_LAS_2019/ Number of files: 3541

These files were processed to the Data Access Viewer (DAV) and https. The total number of files downloaded and processed was 14,829.

Hydro breaklines are also available. These data are available for download at the link provided in the URL section of this metadata record. Please note that these products have not been reviewed by the NOAA Office for Coastal Management (OCM) and any conclusions drawn from the analysis of this information are not the responsibility of NOAA or OCM.

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 Reflectance 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 foot cell size. These lidar point cloud data were used to create Reflectance Images, 3D breaklines, and hydro-flattened DEMs as necessary.

USGS Contract No. G16PC00020 CONTRACTOR: Dewberry SUBCONTRACTOR: Harris Corporation Lidar data were acquired and calibrated by Harris Coporation. All follow-on processing was completed by the prime contractor.

ldrspec>U.S. Geological Survey (USGS) - National Geospatial Program (NGP) Lidar Base Specification v1.2</ldrspec>

<ldrsens>Harris GmAPD Mapping LiDAR Sensor</ldrsens>

<ldrmaxnr>1 per detector (4096 detectors</ldrmaxnr>

<ldrnps>0.5</ldrnps>

<ldrdens>4</ldrdens>

<ldranps>0.35</ldranps>

<ldradens>8</ldradens>

<ldrfltht>7620</ldrfltht>

<ldrfltsp>240</ldrfltsp>

<ldrscana>15</ldrscana>

<ldrscanr>17.7</ldrscanr>

<ldrpulsr>50</ldrpulsr>

<ldrpulsd>0.46</ldrpulsd>

<ldrpulsw>0.138</ldrpulsw>

<ldrwavel>1064</ldrwavel>

<ldrmpia>1</ldrmpia>

<ldrbmdiv>0.05</ldrbmdiv>

<ldrswatw>3810</ldrswatw>

<ldrswato>55</ldrswato>

<ldrgeoid>National Geodetic Survey (NGS) Geoid12B</ldrgeoid>

</ldrinfo>

-<ldraccur>

<ldrchacc>0.939</ldrchacc>

<rawnva>0.101</rawnva>

<rawnvan>114</rawnvan>

<clsnva>0.101</clsnva>

<clsnvan>116</clsnvan>

<clsvva>0.102</clsvva>

<clsvvan>79</clsvvan>

</ldraccur>

-<lasinfo>

<lasver>1.4</lasver>

<lasprf>6</lasprf>

<laswheld>The Withheld bit was not used as it is not applicable to a Geiger-mode sensor.</laswheld>

<lasolap>The Overlap bit was not used as it is not applicable to a Geiger-mode sensor.</lasolap>

<lasintr>16</lasintr>

-<lasclass>

<clascode>1</clascode>

<clasitem>Processed, but Unclassified</clasitem>

</lasclass>

-<lasclass>

<clascode>2</clascode>

<clasitem>Bare Earth Ground</clasitem>

</lasclass>

-<lasclass>

<clascode>3</clascode>

<clasitem>Low Vegetation</clasitem>

</lasclass>

-<lasclass>

<clascode>4</clascode>

<clasitem>Medium Vegetation</clasitem>

</lasclass>

-<lasclass>

<clascode>5</clascode>

<clasitem>High Vegetation</clasitem>

</lasclass>

-<lasclass>

<clascode>6</clascode>

<clasitem>Buildings</clasitem>

</lasclass>

-<lasclass>

<clascode>7</clascode>

<clasitem>Low Noise</clasitem>

</lasclass>

-<lasclass>

<clascode>9</clascode>

<clasitem>Water</clasitem>

</lasclass>

-<lasclass>

<clascode>10</clascode>

<clasitem>Ignored Ground</clasitem>

</lasclass>

-<lasclass>

<clascode>17</clascode>

<clasitem>Bridge Decks</clasitem>

</lasclass>

-<lasclass>

<clascode>18</clascode>

<clasitem>High Noise</clasitem>

</lasclass>

</lasinfo>

Any conclusions drawn from the analysis of this information are not the responsibility of Dewberry, Harris Corporation, Ayers Associates, USGS, 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.

Fifty-four checkpoints were determined to be photo-identifiable in the intensity imagery and were used to test the horizontal accuracy of the lidar dataset. 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.

This data set was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 41 cm RMSEx/RMSEy Horizontal Accuracy Class which equates to Positional Horizontal Accuracy = +/- 1 meter at a 95% confidence level. Actual positional accuracy of this dataset was found to be RMSEx = 41 cm (1.34 ft) and RMSEy = 35.6 cm (1.17 ft) which equates to +/- 93.9 cm (3.08 ft) at 95% confidence level.

The project specifications require that only Non-Vegetated Vertical Accuracy (NVA) be computed for raw lidar point cloud swath files. The required accuracy (ACCz) is: 19.6 cm (0.64 ft) at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm (0.33 ft) in the “bare earth” and "urban" land cover classes. The NVA was tested with 114 checkpoints located in bare earth and urban (non-vegetated) areas. These check points were not used in the calibration or post processing of the lidar point cloud data. The checkpoints were distributed throughout the project area and were surveyed using GPS techniques. See survey report for additional survey methodologies. Elevations from the unclassified lidar surface were measured for the x,y location of each check point. Elevations interpolated from the lidar surface were then compared to the elevation values of the surveyed control points. AccuracyZ has been tested to meet 19.6 cm (0.64 ft) or better Non-Vegetated Vertical Accuracy at 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines.

Tested 0.101 meters (0.33 ft) NVA at a 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA). The NVA of the raw lidar point cloud swath files was calculated against TINs derived from the final calibrated and controlled swath data using 114 independent checkpoints located in Bare Earth and Urban land cover classes.

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.