2015 USGS Lidar: Gratiot County, MI

Geographic Extent: Gratiot County, MI, covering approximately 572 square miles.

Dataset Description: Gratiot County, MI 2015 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. The data was developed based on a horizontal projection/datum of Michigan State Plane South, NAD83, international feet and vertical datum of NAVD1988 (GEOID12A), international feet. LiDAR data was delivered in RAW flight line swath format, then processed to create Classified LAS 1.4 Files formatted to 695 individual 5000 foot X 5000 foot tiles. Corresponding Intensity Images and Bare Earth DEMs tiles were created with the same 5000 foot X 5000 foot tile schema. Breaklines were produced in Esri geodatabase format.

Ground Conditions: LiDAR was collected in spring of 2015, 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, Quantum Spatial established a total of 91 Land Cover control points (71 QC checkpoints, 20 calibration control points) which were used to calibrate the LIDAR to known ground locations established throughout the Gratiot County, MI project area.

The NOAA Office for Coastal Management (OCM) downloaded 695 laz point data files from this USGS site:

https://rockyweb.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/USGS_LPC_MI_GratiotCo_2015_LAS_2017/laz/

The data were processed to the Data Access Viewer (DAV) to make the data available for custom downloads.

The purpose of these lidar data was to produce high accuracy 3D hydro-flattened Digital Elevation Model (DEM) with a 5 foot cell size.

USGS Contract: G10PC00026 Task Order Number: G15PD00343

CONTRACTOR: Quantum Spatial

Lidar data were acquired and calibrated by the prime contractor.

All follow-on processing was completed by the prime contractor.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

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

"ldrsens" : "Leica ALS 70 Serial Number 7161",

"ldrmaxnr" : "4",

"ldrnps" : "0.65",

"ldrdens" : "2.19",

"ldranps" : "0.65",

"ldradens" : "2.19",

"ldrfltht" : "2100",

"ldrfltsp" : "140",

"ldrscana" : "20",

"ldrscanr" : "37.7",

"ldrpulsr" : "261",

"ldrpulsd" : "4",

"ldrpulsw" : "0.48",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.22",

"ldrswatw" : "1528.67",

"ldrswato" : "9.97",

"ldrgeoid" : "National Geodetic Survey (NGS) Geoid12A"

},

"ldraccur" : {

"ldrchacc" : "0.196",

"rawnva" : "0.094",

"rawnvan" : "40",

"clsnva" : "0.102",

"clsnvan" : "40",

"clsvva" : "0.076",

"clsvvan" : "31"

},

"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" : "11-bit",

"lasclass" : {

"clascode" : "1",

"clasitem" : "Undetermined/Unclassified"

},

"lasclass" : {

"clascode" : "2",

"clasitem" : "Bare earth"

},

"lasclass" : {

"clascode" : "7",

"clasitem" : "Low noise"

},

"lasclass" : {

"clascode" : "9",

"clasitem" : "Water"

},

"lasclass" : {

"clascode" : "10",

"clasitem" : "Ignored Ground"

},

"lasclass" : {

"clascode" : "17",

"clasitem" : "Bridges"

},

"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 or 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.

MicroStation Version 8; TerraScan Version 15; TerraModeler Version 15; GeoCue Version 2014.1.21.1; ESRI ArcGIS 10.2; Global Mapper 16; Leica Cloud Pro 1.2; Windows 7 Operating System

\\psihq_nx3200\Projects\26242_Gratiot_Co\ 42.1 GB and

\\Matrix\LIDAR\26242_Gratiot_Co\ 398 GB

The specifications require that only Nonvegetated Vertical Accuracy (NVA) be computed for raw lidar point cloud swath files. The vertical accuracy was tested with 40 independent survey located in open terrain. These check points (check points) were not used in the calibration or post processing of the lidar point cloud data. The survey check points were distributed throughout the project. Specifications for this project require that the NVA be 19.6 cm or better AccuracyZ at 95 percent confidence level.

The NVA was tested using 40 independent surveys located in open terrain. The survey check points were distributed throughout the project area. The 40 independent check points were surveyed using the closed level loop technique. 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.

The RMSE was computed to be 0.162 international feet (4.9 cm). AccuracyZ has been tested to meet 19.6 cm Nonvegetated Vertical Accuracy at 95 percent confidence level using (RMSEz * 1.9600) as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines.

These raw 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 Nonvegetated Vertical Accuracy specifications.

Data cover the entire area specified for this project.

Data is backed up to tape and to cloud storage.

Data were collected and processed by Quantum Spatial, Inc. and made available on the USGS ftp site. The data were downloaded from the USGS ftp site by the NOAA Office for Coastal Management (OCM) where the data were processed to make it available for custom download from the Data Access Viewer (DAV).