2001 USACE LRE Topobathy Lidar: Lake Ontario (NY)

NOAA Office for Coastal Management received the 2001 Lake Ontario dataset with 2 separate metadata records in 2013 on a hard-drive device from the USGS Center for LiDAR Information Coordination and Knowledge (CLICK); the first record was for the topographic portion of the shoreline from the USACE Detroit Office collected in May of 2001 and a second stating the USACE JALBTCX SHOALS system as having collected the bathymetric points for these same areas in August of 2001. The collection dates and GPS times correspond to each having successfully collected and delivered their respective areas. This record is a combination of the two and will highlight sections from both in order to create a complete and complementary metadata record. The original metadata records will be available by request only.

This data set is the raw topographic LIDAR data set. The data set contains selected base categories of geographic features, and characteristics of these features (X,Y,Z), in digital form. The X,Y represent geographic coordinates and the Z represents elevation in meters. The information was collected by EarthData International, LLC for the U.S. Army Corps of Engineers, Detroit District. This collection was done on the behalf of the Lake Ontario St. Lawrence River Study by the International Joint Commission.

These data were collected by the SHOALS (Scanning Hydrographic Operational Airborne Lidar Survey) system which consists of an airborne laser transmitter/receiver capable of measuring 400 soundings per second. The system operates from a deHavilland DHC-6 Twin Otter flying at altitudes between 200 and 400 meters with a ground speed of about 100 knots. The SHOALS system also includes a ground-based data processing system for calculating accurate horizontal position and water depth. Lidar is an acronym for LIght Detection And Ranging. The system operates by emitting a pulse of light that travels from an airborne platform to the water surface where a small portion of the laser energy is backscattered to the airborne receiver. The remaining energy at the water's surface propagates through the water column and reflects off the sea bottom and back to the airborne detector. The time difference between the surface return and the bottom return corresponds to water depth. The maximum depth the system is able to sense is related to the complex interaction of radiance of bottom material, incident sun angle and intensity, and the type and quantity of organics or sediments in the water column. As a rule-of-thumb, the SHOALS system should be capable of sensing bottom to depths equal to two or three times the Secchi depth.

The purpose for the topographic collection of raw Topographic LIDAR, was to support coastal and water modeling of the Lake Ontario South Shore shoreline. This was conducted as part of a study by the Lake Ontario - St. Lawrence River Study by the International Joint Commission.

The purpose of the bathymetric survey was to collect data from the shoreline to approximately -10m depths. The data will be used to build models of the Lake Ontario shoreline.

10524

A footprint of the entire dataset is available here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4700/supplemental/ny2001_usace_loslrs_ontario_m4700.kmz

A footprint of the bathymetric data is available here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4700/supplemental/ny2001_usace_loslrs_ontario_m4700_bathy.kmz

A report concerning the control points is available here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4700/supplemental/ny2001_usace_loslrs_ontario_m4700_surveyreport.pdf

LiDAR points in LAZ format (Classes 1,2,11)

none

Any conclusions drawn from the analysis of this information are not the responsibility of LOSLR, GLC, USACE, JALBTCX, NOAA, the Office for Coastal Management or its partners.

This data can be obtained on-line at the following URL:

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=4700;

None

These data depict the heights at the time of the survey and are only accurate for that time. Acknowledgment of the Joint Airborne Lidar Bathymetry Technical Center of eXpertise (JALBTCX) would be appreciated in any publications or derived products. The data herein, including but not limited to geographic data, tabular data, analytical data, electronic data structures or files, are provided "as is" without warranty of any kind, either expressed or implied, or statutory, including, but not limited to, the implied warranties or merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the data is assumed by the user. No guarantee of accuracy is granted, nor is any responsibility for reliance thereon assumed. In no event shall the U.S. Army Corps of Engineers, Mobile District Office, Spatial Data Branch be liable for direct, indirect, incidental, consequential or special damages of any kind, including, but not limited to, loss of anticipated profits or benefits arising out of use of or reliance on the data. The Spatial Data Branch does not accept liability for any damages or misrepresentation caused by inaccuracies in the data or as a result of changes to the data caused by system transfers or other transformations or conversions, nor is there responsibility assumed to maintain the data in any manner or form.

The raw digital elevation model (DEM) was generated for the project area from the raw data. This raw DEM includes elevations for vegetation and buildings. The raw DEM was further processed to an even 4-m interval in both the latitude and longitude direction by "gridding" the data. The raw DEM was derived with an accuracy to support the generation of 0.6-m (2') contours at National Map Accuracy Standards (NMAS).

SHOALS has demonstrated capabilities that meet US Army Corps of Engineers Hydrographic Survey accuracy requirements for Class 1 surveys and the International Hydrographic Organization nautical charting standards for Order 1.

One simultaneous adjustment was performed on the entire data set to ensure that all coordinates and adjustments were unique to one network.; Quantitative Value: 3 meters, Test that produced the value: +/- 3 meters (1 sigma)

GPS and IMU data collection for the first mission began at 19:50 May 09, 2001 GMT and ended at 00:45 on May 10, 2001, GMT. The LIDAR data collection began at 20:45

GMT (334000 week second) and continued until 00:05 GMT (345900 week second). During that time there were no significant cycle slips in the data collected at the

Genessee airport nor in the data collected onboard the aircraft. There were 2 data gaps in the data collected by Costage Engineering. However this did not significantly impact the differential solution. The aircraft did not travel more than 50 statute miles from either base station. During the LIDAR data collection the PDOP was less than 2.5 and the DDOP was less than 4.

The phase differential solution from the data collected at the Genessee airport is a fixed integer solution. Ionospheric error modeling was selected in the post processing software for this data set. The "forward" and "reverse" solutions were compared to each other and are nearly identical. These 2 trajectory files were averaged together to yield the final solution (solution A). The phase differential solution from the data collected by Costage Engineering, located at the project site, is a "float" solution. This is due to the large distance from the Genessee airport to the project area at the time of GPS initialization. Ionospheric error modeling was selected in the post processing software for this data set. The forward and reverse solutions were compared to each other. The differences in the 2 solutions were well within acceptable tolerances. These two were averaged together to yield a single trajectory file (solution B).

To determine the overall quality and accuracy of the GPS data collection and subsequent processing solutions A and B were compared to each other. The differences between these 2 trajectory files were well within acceptable tolerances. The small difference between these 2 solutions indicates that the GPS positioning of the aircraft is valid and exceeds the precision required for this project. The IMU data collection for the entire flight was continuous. The static initialization of the IMU was not less than 10 minutes. This is more than 3 times the minimum amount of time recommended by Applanix Corporation. The post processing of the IMU data indicates that the resulting Smoothed Best Estimate Trajectory (SBET) was free of anomalies and yielded the best position and orientation that the system can provide.

Solution A was used with the IMU data for all subsequent LIDAR data processing for Area 1.; Quantitative Value: 0.15 meters, Test that produced the value: +/- 15 cm (1 sigma)

The raw LIDAR dataset required a substantial amount of editing since the project area was flown so late in the spring. Much of the vegetation had "leafed-out", so there were a number of areas where it was difficult to distinguish the low-lying vegetation from the surface of the ground.

Point topological relationships are collected or generated to satisfy topological requirements. Some of the requirements include populated X coordinate, Y coordinate, and Z coordinate values all with in NMAS.