New York Office of Information Technology Services
Unpublished Material
LIDAR collection (QL2) for Erie, Genesee, and Livingston Counties New York Lidar; Classified Point Cloud
Lidar point cloud
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.
USGS-NGP Base Lidar Specification v1.3
Riegl LMS Q1560 S2221262 LiDAR System (Axis GeoAviation, LLC.)
7
.7
2.31
.7
2.31
2134
170
58.52
400
88.9
3
.535
1064
1
0.25
2285
20
NAD 1983(2011) Conus Albers Meters
National Geodetic Survey (NGS) Geoid12B
0.191
.053
111
1.4
6
Withheld (ignore) points were identified in these files using the standard LAS Withheld bit.
Swath "overage" points were identified in these files using the standard LAS overlap bit.
16
1
Processed, but Unclassified
2
Bare Earth Ground
7
Low Noise
9
Water
17
Bridge Decks
18
High Noise
20
Ignored Ground
20190425
20190515
ground condition
None planned
-79.18841
-77.384061
43.276981
42.241447
None
Breaklines
Elevation Data
Lidar
None
New York
Erie County
Genesee County
Livingston County
No restrictions apply to these data.
None. However, users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of the limitations of the data. Acknowledgement of New York Office of Information Technology Services would be appreciated for products derived from these data. The data represented is the result of data collection and processing per contract specifications and indicates the general existing conditions at the time of the data collection. As such, it is only valid for its intended use, content, time, and accuracy specifications. The user is responsible for the results of any application of the data for other than its intended purpose.
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.
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.
LAS Point Classification: The point classification is performed as described below. The bare earth surface was manually reviewed to ensure correct classification on the Class 2 (Ground) points. After the bare-earth surface was finalized, breaklines for hydrography and underneath bridges were digitized. Hydro breaklines were compiled for rivers and streams over 30 m wide and for lakes and ponds greater than 2 acres in area then utilized to generate hydro-flattened water features for the DEMs. The bridge terrain breaklines were captured at the bridge deck level and below along the ground beneath to allow proper flow of hydro through bridges per USGS “LIDAR Base Specification, Version 1.3”. All breaklines were delivered as 3D ESRI shapefiles with attribution for feature types. All ground (ASPRS Class 2) lidar data inside of hydro-breaklines were then classified to water (ASPRS Class 9) using TerraScan macro functionality. A buffer of 1 meter was also used around each hydro-breakline feature to classify these ground (ASPRS Class 2) points to Ignored ground (ASPRS Class 20). All Lake Pond Island and Double Line Drain Island features were checked to ensure that the ground (ASPRS Class 2) points were reclassified to the correct classification after the automated classification was completed. All overlap data was processed through automated functionality provided by TerraScan to appropriately bit flag overlapping flight line data per USGS specifications. All data was manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler. Global Mapper was used as a final check of the bare earth dataset. LP360 was then used to create the deliverable industry-standard LAS files for both the Raw Swath Data and the Classified Tiles. New York Office of Information Technology Services proprietary software was used to perform final statistical analysis of the classes in the LAS files, on a per tile level to verify final classification metrics and full LAS header information.
2019
Point
Albers Conical Equal Area
29.500000
45.500000
-96.00
23.0
0.0
0.0
coordinate pair
0.1
0.1
meters
North American Datum of 1983 (2011)
Geodetic Reference System 80
6378137
298.257222101
North American Vertical Datum of 1988 (Geoid12B)
0.01
meters
Explicit elevation coordinate included with horizontal coordinates
20190330
New York Office of Information Technology Services
mailing and physical
W. Averell Harriman State Office Campus
1220 Washington Avenue, Bldg. 5 – Floor 1
Albany
NY
12226
USA
(518)242-5061
FGDC Content Standard for Digital Geospatial Metadata
FGDC-STD-001-1998