The Problem:

A LiDAR topographic survey of the Carson River corridor was conducted for Carson Water Subconservancy District (CWSD) by BAE Systems/Woolpert. The survey aimed to gather topographic information for river restoration projects along the Carson River. Although the contractor provided an estimate of the vertical accuracy of the resulting dataset, the number of points used for this assessment was fewer than 20.

The Solution:

A quality-assurance survey was conducted to determine whether the vertical accuracy met Federal Emergency Management Agency (FEMA) standards. Additionally, a survey tie-in of the BAE System Network was performed to recover and survey the control points used by the BAE Systems contractor for establishing the existing control network. Verification of the ability to recover and verify the coordinates used for the control network in the LiDAR survey was a crucial step in validating the LIDAR dataset. Field survey work was conducted to collect the necessary data for extracting elevations from the LiDAR dataset.

ARC-Map was used as the tool for processing the LiDAR dataset and constructing a terrain model of the Carson Valley portion of the dataset. The horizontal locations of the field-surveyed points were used to extract elevations from the LiDAR-based terrain model. These elevations were then compared with field-surveyed elevations to evaluate the vertical accuracy of the LiDAR topographic dataset.

The Results:

These elevations were compared with field-surveyed elevations to evaluate the vertical accuracy of the LiDAR topographic dataset. A comprehensive report was generated to document the results and determine the vertical map accuracy of the LiDAR-based topography. The computation of the residual differences between the LiDAR-based elevations and the field-surveyed elevations was completed, along with the calculation of the RMSE to validate the LiDAR-based elevations. More projects have been added for Lyon County because of the successful LiDAR validation project, which now covers over 80 miles and involves 10 different public agencies.

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