Santa Clara County, California

LAS format files, raw LiDAR data in its native format, classified bare-earth LiDAR DEM and photogrammetrically derived breaklines generated from LiDAR Intensity stereo-pairs. Breakline, Top of Bank, and contour files in ESRI personal geodatabase format, Microstation V8 .dgn format, and AutoCAD 2004 formats for the San Jose Phase 3 project of Santa Clara County, Ca. This project arrived with only unclassified data. NOAAs Office for Coastal Management performed an automated classification using lasground. Although class 1 and class 2 are available, there was no QA/QC on the points after lasground was performed. Points below -40 meters NAD83 ellipsoid height were further classified as noise (class 7).

The purpose of the bare-earth LiDAR Point and Breakline data is to provide ground surface data and one-foot (Valley Area) and five-foot (Mountain Areas) contour generation, and the delineation of watercourse ( Top of Bank ).

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A report for this project is available at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4870/supplemental/ca2006_scwd_santaclara_m4870_surveyreport.pdf

A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4870/supplemental/ca2006_scwd_santaclara_m4870.kmz

LAS 1.2 format (classes 1,2,7)

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Any conclusions drawn from the analysis of this information are not the responsibility of Aerometric, INC., USGS, NOAA, the Office for Coastal Management or its partners. No QA/QC was performed after automated classification using lasground.

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

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=4870

The data set is dynamically generated based on user-specified parameters.;

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The DTM data represents the results of data collection/processing for Santa Clara, California and indicates the existing general conditions. As such, they are only valid for their intended use, content, time and accuracy specifications. The user is responsible for the results of any application of data other than its intended purposes.

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be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions.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. These data depict the heights at the time of the survey and are only accurate for that time.

LiDAR DEMs to support 1' contours have a maximum RMSE of 9 centimeters, which is roughly equivalent to 0.6' accuracy with a 95% confidence. Field verification of the vertical accuracy of the LiDAR DEM was conducted to ensure that the 9-centimeter RMSE requirement was satisfied for all major vegetation categories that were predominate within the 1' contour area. | Quantitative Value: NSSDA 95% Confidence: 0.6' | Quantitative Test Explanation: The RMSE calculated from a sample of test points is not the RMSE of the DEM. The calculated value may be higher or it may be lower than that of the DEM. Confidence in the calculated value increases with the number of test points. If the errors (lack of accuracy) associated with the DEM are normally distributed and unbiased, the confidence in the calculated RMSE can be determined as a function of sample size. Similarly, the sample RMSE necessary to obtain 95-percent confidence that the DEM RMSE is less than 9 centimeters can also be determined as a function of sample size. Optimal Geomatics collected test points using RTK (Real-Time Kinematic) GPS techniques. Over one hundred and twenty points were collected in total over various terrain classes. All RMSE calculations were performed on the bare-earth, orthometric surface.

No specific testing was done to determine horizontal accuracy of the DTM. Test results for vertical accuracy tend to show that the 0.75m (2.46 US survey feet) RMSE horizontal accuracy tolerance determined by system studies and other methods was met or exceeded.; Quantitative Value: 0.75 meters, Test that produced the value: Expected horizontal accuracy of elevation products as determined from system studies and other methods is 1/2000th of the flight height, which in the instance of this particular project was 1500m (4921.2 US survey feet) AGL, giving a horizontal tolerance of less than 0.75 m (2.46 US survey feet).

Tested to meet 0.183 m vertical accuracy at 95 percent confidence level.; Quantitative Value: 0.183 meters, Test that produced the value: Tested 18.3 cm in open terrain at ninety-five percent confidence level using RMSE(z) x 1.9600.

Each strip was imported into a project using TerraScan (Terrasolid, Ltd.) and the project management tool GeoCue (GeoCue Corp.). By creating a project, the various flightlines are combined while breaking the dataset as a whole into manageable pieces. This process also converts the dataset from geographic coordinates to the State Plane Coordinate System (NAD83), California III. The ellipsoid height values were converted to NAVD88 orthometric values using Geoid03, provided by NGS. Individual lines were then checked against adjacent lines to ensure a cohesive dataset. The data from each line were then combined and a classification routine was then run to determine the initial surface model. This initial surface model was then reduced using Optimal Geomatics' proprietary methods to create the final bare-earth dataset. A Triangular Irregular Network (TIN) was generated using the final surface data. Contours were then created from the TIN. The bareearth data were then checked against the validation points across the project area. The results of these checks showed the DEM fitting the validation points well (see LiDAR DEM Quality Control Report for results). Stereo pairs were generated from the LiDAR intensity data using Geocue and LiDAR1CuePac (GeoCue Corp.). LiDARgrammetry was then utilized to collect breaklines where necessary along hydro features to support the contour generation. These breaklines were collected as a 3D element in the MicroStation (Bentley Systems, Inc.) environment utilizing ISSD (Z/I Imaging). The breaklines, top of bank (TOB), contour files were delivered in MicroStation v8, AutoCAD 2004 and ESRI Personal GeoDatabase formats. The LiDAR point data were delivered in LAS and ASCII formats. LiDAR orthos were delivered in TIF/TFW format.

LiDAR was classified and stereo-pairs were generated from LiDAR intensity data which were used to collect breaklines and top of bank. A surface was generated from the bare earth LiDAR DTM and collected breakline data to produce 1', 5', 10' and 25' contours in pre-assigned areas designated by the client.