Quantum Spatial
20180709
NYC 2017 LiDAR Topographic Hydroenforced Filled DEM (mosaic)
raster digital data
The hydro-flattened and enforced bare earth digital elevation model (DEM) represents the earth's surface with all vegetation and anthropogenic features removed. It is derived from NIR LiDAR data using TIN processing of the ground point returns. All rivers greater than 20 feet in width and lakes at least 0.25 acres in size have been flattened to consistent elevations. Some smaller streams and ponds were also flattened when deemed appropriate. Water boundary polygons were developed using an algorithm which weights LiDAR-derived slopes, intensities, and return densities to detect the water's edge. Elevation values were then assigned to the water's edge from the LiDAR data creating 3D breaklines enforced during model creation to flatten water bodies. Additionally, hydro-enforcement breaklines were created at all artificial obstructions to flow found in the ground model (i.e. culverts) to break the obstruction and allow flow to continue. Some elevation values have been interpolated across areas in the ground model where there is no elevation data (e.g. under dense vegetation). This version of hydroenforced DEM has had sinks filled. Another version of hydroenforced DEM has been provided without sinks filled. The horizontal datum for this dataset is NAD83, the vertical datum is NAVD88, Geoid 12B, and the data is projected in New York State Plane - Long Island. Units are in US Survey Feet. Quantum Spatial collected the New York City LiDAR data for The City of New York between 05/03/17 and 05/17/17.
Provide high resolution terrain elevation data from the New York City dataset.
This data is assembled by AOI and projected in New York State Plane - Long Island.
20170503
20170517
New York City LiDAR
None planned
-74.258339
-73.698030
40.916459
40.495081
None
LiDAR, Light Detection and Ranging, elevation data, topography, bare earth, hydro-flattened, hydro-enforced, breaklines, DEM, digital elevation model
ISO 19115 Topic Categories
elevation
None
New York City
New York
NYC, Manhattan, Brooklyn, Queens, The Bronx, Staten Island
None
In some areas of heavy vegetation or forest cover, there may be relatively few ground points in the LiDAR data. TINing the points produces large triangles and hence the elevations may be less accurate within such areas. Elevation values for open water surfaces are derived from waters edge breaklines. Triangles were created across water surfaces by interpolating from the nearest breakline elevation points. Due to some very large buildings within the city, there are very large triangles/interpolation thoughout. Mosaicking lines and "cross hairs" may be seen in the middle of some interpolation. This is normal and will not affect the quality of the data. Wooden boardwalks and concrete boardwalks which are known to be on pylons and where separation is clearly visible, were removed from the bare earth models.
The City of New York
DoITT
Mailing
2 Metro Tech, 4th Floor
Brooklyn
New York
11201
US
718-403-8214
Gis-mgt@doitt.nyc.gov
The City of New York
Environment as of Metadata Creation: Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Esri ArcGIS 10.4.1 (Build 5686) Service Pack N/A (Build N/A)
No formal attribute accuracy tests were conducted.
Shaded relief images have been visually inspected for data errors such as pits, border artifacts, and shifting. LiDAR flightlines have been examined to ensure consistent elevation values across overlapping flightlines. The Root Mean Square Error (RMSE) of line to line relative accuracy for this dataset is 0.085 ft (0.026 m). Please see the LiDAR data report for a discussion of the statistics related to this dataset.
LiDAR data has been collected and processed for all areas within the project study area.
A formal accuracy assessment of the horizontal positional information in the data set has not been conducted.
The Non-vegetated Vertical Accuracy (NVA) of this dataset, tested at 95% confidence level is 0.242 ft (0.074 m). Please see the LiDAR data report for a discussion of the statistics related to this dataset.
0.242 ft (0.074 m)
Non-vegetated Vertical Accuracy was assessed using 151 ground check points. These check points were not used in the calibration or post processing of the LiDAR point cloud data.
Acquisition. Quantum Spatial collected the New York City LiDAR data between 05/03/17 and 05/17/17. The survey used a Leica ALS80 laser system mounted in a Cessna 402C. Ground level GPS and aircraft IMU were collected during the flight.
Sensor: Leica ALS80
Maximum returns: Unlimited
Nominal pulse density: 8 pulses/m^2
Nominal pulse spacing: 0.35 m
AGL: 1800 m
Speed: 145 knots
FOV: 28°
Scan frequency: 48 hz
Pulse rate: 314.8 kHz
Pulse duration: 2.5 ns
Pulse width: 39.6 cm
Wavelength: 1064 nm
Pulses in air mode: Multiple Pulses in Air
Beam divergence: 22 mrads
Swath width: 898 m
Overlap: 60%
20170517
1. Flightlines and data were reviewed to ensure complete coverage of the study area and positional accuracy of the laser points.
2. Laser point return coordinates were computed using Waypoint Inertial Explorer and Leica Cloudpro software based on independent data from the LiDAR system, IMU, and aircraft.
3. The raw LiDAR file was assembled into flightlines per return with each point having an associated x, y, and z coordinate.
4. Visual inspection of swath to swath laser point consistencies within the study area were used to perform manual refinements of system alignment.
5. Custom algorithms were designed to evaluate points between adjacent flightlines. Automated system alignment was computed based upon randomly selected swath to swath accuracy measurements that consider elevation, slope, and intensities. Specifically, refinement in the combination of system pitch, roll, and yaw offset parameters optimize internal consistency.
6. Noise (e.g., pits and birds) was filtered using post-processing software, based on known elevation ranges and included the removal of any cycle slips.
7. Using TerraScan and Microstation, ground classifications utilized custom settings appropriate to the study area.
8. The corrected and filtered return points were compared to the ground survey points collected to verify the vertical accuracy.
9. TIN processing of the ground point returns with water's edge and hydro-enforcement breaklines enforced was used to create this hydro-flattened and enforced bare earth DEM.
20180308
Raster
Pixel
153378
154859
NAD 1983 StatePlane New York Long Island FIPS 3104 Feet
40.66666666666666
41.03333333333333
-74.0
40.16666666666666
984250.0
0.0
coordinate pair
0.00000002687262634637478
0.00000002687262634637478
foot_us
D North American 1983
GRS 1980
6378137.0
298.257222101
The City of New York
DoITT
Mailing
2 Metro Tech, 4th Floor
Brooklyn
New York
11201
US
718-403-8214
Gis-mgt@doitt.nyc.gov
Please contact The City of New York for information regarding the use of this data.
None. No fees are applicable for obtaining the data set.
20190116
Quantum Spatial
Mailing and Physical
1100 NE Circle Blvd., Suite 126
Corvallis
OR
97330
US
541-752-1204
FGDC Content Standard for Digital Geospatial Metadata
FGDC-STD-001-1998
local time