2017 NYS Lidar: Southwest NY (Spring)

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

Geographic Extent: Chautauqua and Cattaraugus County, New York, covering approximately 1,722 square miles.

Dataset Description: Chautauqua and Cattaraugus County, New York 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. The data was developed based on a horizontal projection/datum of NAD83(2011), Universal Transverse Mercator Zone 17 N, meters and vertical datum of NAVD88 (GEOID12B), meters. Lidar data was delivered as flightline-extent unclassified LAS swaths, as processed Classified LAS 1.4 files, formatted to 1982 individual 1500 m x 1500 m tiles, as tiled bare earth DEMs; all tiled to the same 1500 m x 1500 m schema.

Ground Conditions: Lidar was collected in early 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, New York Office of Information Technology Services established a total of 32 ground control points that were used to calibrate the lidar to known ground locations established throughout the Chautauqua and Cattaraugus County, New York project area. An additional 128 independent accuracy checkpoints, 75 in Bare Earth and Urban landcovers (75 NVA points). 53 in Tall Grass and Brushland/Low Trees categories (53 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 1982 laz files from this USGS site:

ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/USGS_LPC_NY_Southwest_East_2017_LAS_2018/ and processed the data to the Data Access Viewer (DAV) and to https.

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 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, intensity images, 3D breaklines, hydro-flattened DEMs as necessary.

USGS Contract No. G17AC00096 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 v1.2",

"ldrsens" : "Riegl Q1560 LiDAR System (Axis GeoSpatial LLC)",

"ldrmaxnr" : "7",

"ldrnps" : ".76",

"ldrdens" : "2.87",

"ldranps" : ".71",

"ldradens" : "2.0",

"ldrfltht" : "2469",

"ldrfltsp" : "145",

"ldrscana" : "58.52",

"ldrscanr" : "84.3",

"ldrpulsr" : "766",

"ldrpulsd" : "5",

"ldrpulsw" : ".60",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "2561",

"ldrswato" : "20",

"ldrcrs" : "NAD 1983(2011) UTM Zone 17N Meters",

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

},

"ldraccur" : {

"ldrchacc" : "0.3887",

"rawnva" : "0.048",

"rawnvan" : "75"

},

"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" : "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 the New York Office of Information Technology Services, 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.

NYS Office of Information Technology Services horizontal accuracy assessment:

Early in the review process, an intensity image was made from all tiles. In select areas, the horizontal position of features such as sidewalk corners, painted lines, and pavement intersections on this intensity image were compared to the locations of the same features on reference data. In most cases, the reference data were orthoimages or vector data digitized from the orthoimagery. In some cases, NYSDOT design scale mapping accurate to +/- 6 cm was also used. Occasionally, the project’s surveyed checkpoints also could be used. This check on the horizontal position of the LIDAR data was done to confirm a reasonable horizontal alignment before starting detailed vertical accuracy checks.

Horizontal accuracy better than +/- 4-ft at 95%.

Axis surveyed 128 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 75 points in the nonvegetated vertical accuracy (NVA) group and 53 points in the vegetated vertical accuracy (VVA) group. For the ~4459 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. The NVA RMSE is 4.4 cm.

NYS Office of Information Technology Services vertical accuracy assessment:

To increase our ability to evaluate the vertical quality of the LIDAR-derived surface, we used data from NYSDOT mapping projects. 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. Using 474 points the RMSE = 7.44 cm.

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. Points with extreme elevations (negative values, or positive values well above the expected maximum) are present in this dataset. These points are classified as low or high noise in classified point cloud tiles.

Data covers the entire area specified for this project.

Data is backed up to tape and to cloud storage.