2019 New York State Lidar: Erie, Genesee, and Livingston Counties

Product: Calibrated LiDAR version 1.4 .las tiles, classified to bare earth for subsequent derivatives.

Geographic Extent: Erie, Genesee, and Livingston Counties, New York, covering approximately 2,188 square miles.

Dataset Description: Erie, Genesee, and Livingston Counties, New York 2019 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 USGS LIDAR Base Specifications Version 1.3. The data was developed based on a horizontal projection/datum of NAD83(2011), Conus Albers, meters and vertical datum of NAVD88 (GEOID12B), meters. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 5667 individual 1000 m x 1000 m tiles, as tiled bare earth DEMs; all tiled to the same 1000 m x 1000 m schema.

Ground Conditions: Lidar was collected in the spring 2019, 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, New York Office of Information Technology Services provided a total of 44 ground control points that were used to calibrate the lidar to known ground locations established throughout the Erie, Genesee, and Livingston Counties, New York project area. An additional 214 checkpoints, 111 NVA in Bare Earth and Urban landcover and 103 VVA in Tall Grass and Brushland/Low Trees categories were surveyed by Axis Geospatial, LLC to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data. 4 of the 111 NVA checkpoints fell beyond the contracted project limits and were not used for the NVA assessment of the DEMs but were used for the NVA assessment of the swaths.

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 Breaklines and Raster DEM. The purpose of these lidar data was to produce high accuracy 3D hydro-flattened Digital Elevation Model (DEM) with a 1 meter cell size. These raw lidar point cloud data were used to create classified lidar LAS files, 3D breaklines, hydro-flattened DEMs as necessary.

USGS Contract No. G19AC00123 CONTRACTOR: New York Office of Information Technology Services. SUBCONTRACTOR: Axis Geospatial, LLC Lidar data were acquired and calibrated by Axis GeoSpatial, LLC. All follow-up processing was completed by the prime contractor.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "USGS-NGP Base Lidar Specification v1.3",

"ldrsens" : "Riegl VQ1560i S2223544 LiDAR System (Axis GeoAviation, LLC.)",

"ldrmaxnr" : "7",

"ldrnps" : ".7",

"ldrdens" : "2.63",

"ldranps" : ".7",

"ldradens" : "2.63",

"ldrfltht" : "1768",

"ldrfltsp" : "150",

"ldrscana" : "58.52",

"ldrscanr" : "500",

"ldrpulsr" : "125",

"ldrpulsd" : "3",

"ldrpulsw" : ".47",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "1902",

"ldrswato" : "20",

"ldrcrs" : "NAD 1983(2011) Conus Albers Meters",

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

},

"ldraccur" : {

"ldrchacc" : "0.0",

"rawnva" : "0.0",

"rawnvan" : "0.0"

},

"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" : "7",

"clasitem" : "Low Noise"

},

"lasclass" : {

"clascode" : "9",

"clasitem" : "Water"

},

"lasclass" : {

"clascode" : "17",

"clasitem" : "Bridge Decks"

},

"lasclass" : {

"clascode" : "18",

"clasitem" : "High Noise"

},

"lasclass" : {

"clascode" : "20",

"clasitem" : "Ignored Ground"

}

}}

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.

The below is taken from: The NYS Office of Information Technology Services - GIS Program Office In Partnership with NYS Department of Transportation – Photogrammetry Section "Final Quality Review Report." That report is linked in this metadata record, and contains additional accuracy information.

Axis surveyed 214 checkpoints independently of the control points used in calibrating the swath data. These checkpoints were well distributed over the project. A range of land cover types were included, with 111 points in the non-vegetated vertical accuracy (NVA) group and 103 points in the vegetated vertical accuracy (VVA) group. 4 of the 111 NVA checkpoints fell beyond the contracted project limits and were not used for the NVA assessment of the DEMs but were used for the NVA assessment of the swaths. For the ~5667 km2 project, this number of checkpoints meets the number recommended in “ASPRS Accuracy Standards for Digital Geospatial Data”.

The surveyed checkpoints showed an acceptable vertical accuracy of the bare earth surface from the classified LAS tiles for Quality Level 2. Using an ESRI LAS dataset, the surface was modeled using a TIN and elevations at checkpoint locations were calculated by “draping” the surface on the points. Results are summarized below.

All Points = 210, RMSE (m) = 0.072930968, 95% (m) = 0.142944697

NVA = 107, RMSE (m) 0.053483363, 95% = 0.104827391

VVA = 103, RMSE (m) = 0.088729117, 95% = 0.173909068

To increase the ability to evaluate the vertical quality of the LIDAR-derived surface, data from NYSDOT mapping projects was used. Control points used in these projects are surveyed to better than +/- 3 cm, while the final photogrammetric mapping is tested to meet vertical accuracies of +/- 6 cm. Using this data source expanded the portions of the project which had quantifiable vertical checks. Given their source and the resulting preponderance of hard surface (NVA) points, the NYSDOT checkpoints were kept separate from the checkpoints discussed above. The results are summarized below.

DOT Surveyed Project Control vs. LAS Bare Earth Surface:

Number of Points: 786

RMSE (m): 0.090969378

95% (m): 0.17829998

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. You may see data voids where caused by areas of low near infrared reflectivity, such as asphalt or composition roofing. We have seen these dropouts on building rooftops throughout this project. Also, there are extreme positive and negative Z values within the LiDAR pointcloud. We have classified these points as Class 7 (Low Point) and/or Class 18 (High Point) to accommodate for these values. Partially elevated water bodies may be present where use of Class 20 (Ignored Ground) next to the hydro breaklines has eliminated ground points on a small berm or raised bank.

Data covers the entire area specified for this project. Partially elevated water bodies may be present where use of Class 20 (Ignored Ground) next to the hydro breaklines has eliminated ground points on a small berm or raised bank.

Data is backed up to tape and to cloud storage.