LiDAR Data Processing for Planet Texas 2050 by Aaron Groth

Aaron Groth is a graduate student in UT’s geography department and a part-time contractor for TARL. This article is part of the September 2018 TARL Newsletter. 

Planet Texas 2050 brings together a multi-disciplinary team of UT researchers to examine issues of sustainability in the state of Texas. Research centers upon urbanization, water, energy, and ecosystem services (e.g., pollination, shade, water filtration, natural carbon sequestration) in the context of a changing climate and increasingly severe weather (e.g., hurricanes and droughts). Geographic Information Systems (GIS) and remote sensing technology can help researchers assess issues of sustainability – looking at past landscapes and human modification to model the future.

An important emerging technology is Light Detection and Ranging (LiDAR), a surveying method that measures distance to a target by illuminating the target with a pulsed laser light and measuring the reflected pulses with a sensor (mounted on aircraft). Differences in laser return times and wave-lengths can then be used to make digital 3-D representation, or “point cloud,” of the target (e.g., vegetation, buildings, and infrastructure, etc.).This data also serves to make 2-D digital elevation models (DEMs) showing detailed topography. DEMs derived from LiDAR available in Texas are at a 50x50cm to 1.5×1.5m spatial resolution. This is far superior to NASA/METI’s
DEMs, which provide a spatial resolution of only 30x30m. LiDAR is an important tool in archaeological research – for example, it has revealed ancient Maya cities and human landscape modifications under the forest canopy of Central America. Furthermore, when there are multiple, time-series LiDAR datasets for an area, it constitutes an important tool for earth and ecosystem sciences – revealing changes in the biophysical environment (loss of glacier mass, changing streambanks, loss of leaves, etc.).

Figure 1. Statewide LiDAR coverage available through TARL’s Planet Texas 2050 partnership.

At TARL, we are building a database of Texas’ available LiDAR data to further archaeological, earth science, and ecology research. Specifically, this database will give Planet Texas 2050 researchers the data they need to answer research questions surrounding the sustainability of population growth and urbanization, water and energy resources, and ecosystem services in the context of a changing climate.

Figure 2. The Austin area as seen through a LiDAR DEM at 140×140 cm spatial resolution. Major buildings, roads, rivers and streams are visible at this resolution.
Figure 3. A zoomed-out view of the Austin area as seen through a NASA/ METI DEM, at a resolution of 30×30 m. Major landscape features such as rivers and hills are visible but manmade landscape modifications are nearly impossible to see at this

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