Research Plan

This project will utilize a multi-agency working group to

• acquire LiDAR and Multispectral Imagery Geospatial Data including
  • a bare earth surface model,
  • raw full width Common LiDAR Data Exchange Format (.LAS) files,
  • a minimum of 1-meter post spacing,
  • the ability to create 1-foot contours,
  • the use of a sensor that is capable of ≥ 4 returns,
  • hydrographic breaklines, and
  • a hydrologically enforced bare earth surface.
• assist with Quality Assurance / Quality Control (QA/QC) including
  • the collection of independent elevation points from differential GpS surveys. These points will be used to validate data in the raw .LAS files and develop a non-partisan root mean square error. Raw LAS files will then be used to evaluate the bare earth surface, breaklines, and hydrologically enforced bare earth surfaces.
  • Metadata will be reviewed for completeness. This is a necessary step to verify the accuracy and precision of the data for its contribution to various threshold-related analyses.
• release post-processed Data products
  • Initial LiDAR and multispectral imagery data products are available to interested agencies.
  • point cloud data are available through the USGS Center for LiDAR Information Coordination and Knowledge, the Tahoe Integrated Information Management System and the Open Topography portal.

Background

The Lake Tahoe Basin, California and Nevada, is around 530 square miles with about 360 square miles of terrestrial and nearshore environments. Much of the current data used for geospatial analysis and modeling in the Lake Tahoe Basin have spatial and temporal limitations that make management decisions and related conclusions difficult. For example, many models use the National Elevation Dataset 10-meter Digital Elevation Model that is derived from the 7.5 minute USGS quadrangles. Structures, anthropogenic landscape alterations, and natural change that occurred after the creation of the 7.5 minute quadrangle are not featured in the data. While these data are valuable as inputs to derive generalized estimates, they lack the level of spatial or temporal refinement necessary to make accurate management decisions about current conditions in the basin.

LiDAR is similar to radar technology in that the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal. This allows the end user to create three-dimensional construction of targeted features such as buildings, infrastructure, vegetation communities, and topographic features. Radar accomplishes this using radio waves while LiDAR uses pulses of light. This technology has been widely applied to forestry, urban planning, archaeology, geography, geology, geomorphology, seismology, remote sensing and atmospheric physics.

Compared to classical aerial photography, multispectral imaging captures light from multiple places in the light spectrum with some being located beyond the visible light range, such as infrared. This allows extraction of additional information that the human eye fails to capture with its receptors for red, green and blue. These additional bands allow for the creation of spectral signatures specific to features such as vegetation vigor, bare earth, and potential moisture. Fusing multispectral data with LiDAR data allows for the integration and convergence of structural and spectral features which opens up a vast number of applied analysis opportunities.