LiDAR Analysis of University of Washington Tacoma's Campus

From urban planning to managing

forests (check out UBC’s Malcolm Knapp

Research Forest data), LiDAR is being

used globally to explore and solve

pressing issues - in three dimensions.

According to NOAA (National Ocean

and Atmoshperic Administration):

"LIDAR, which stands for Light

Detection and Ranging, is a remote

sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth. These light pulses—combined with other data recorded by the airborne system— generate precise, three-dimensional information about the shape of the Earth and its surface characteristics." (Source: oceanservice.noaa.gov/facts/lidar)

Fig. 1: A photograph of Bixby Bridge in Big Sur, CA (Right) and an image created with LiDAR data (Left).

Photo: pcs-structural.com

This analysis will utilize LiDAR data collected by the University of Washington Tacoma regarding the building structures on the campus. The building footprints arrive in the form of a shapefile, and heights are extruded along a Z-axis. This analysis will explore how accurate;y the LiDAR data respresents the relative heights of the buildings in reality.

LiDAR Return Data Rasters

Fig. 2: Orthophoto, downtown

Tacoma, WA.

Fig. 3: Bare Earth returns raster. Bare earth (BE) LiDARE returns measure the height of the ground, or how high above sea level the gorund is.

Fig. 4: All Returns raster. All returns LiDAR data measures the top heights of all returning data including structures, i.e. top of buildings.

Building Footprints

Fig. 5: Shapefile of UWT building footprints.

Fig. 6: Buildings' central points.

Fig. 7: Building shapefile overlayed on Bare Earth raster.

Ground Truthing

Though the LiDAR data is relatively accurate (it is not precise), a few alterations were in order post ground truthing - relative heights in Fig. 10 were compared with visual observations of campus buildings. Figures 11 (shapefile) and 13 (resulting ArcScene with extruded buildings) include new buildings and buildings whose footprint or height in the original data appeared to be different from reality.

New Building

Altered Building

Fig. 11 (Left): New shapefile with new buildings not included in original shapefile in orange and altered buildings, striped.

Table 1 (Above): Building Names and abbreviations from ArcMap attribute table. (Click on table to go to UW Tacoma's campus building website.)

Fig. 13: New ArcScene including new buildings, extruded to minimum heights

ArcScene Analysis

Fig. 8: Orthophoto of UW Tacoma campus in ArcScene (Left).

Fig. 9: Orthophoto of UW Tacoma campus in ArcScene "draped" over a base height using "BE_Grid", or Bare Earth LiDAR data (Right).

Fig. 10: UWT Building footprint shapefile, with a base height using "BE_Grid" and extruded to maximum Z height.

View the Univerisity of Washington Tacoma's Official Campus Map HERE.

Skills Used

- LiDAR data
- Extruding vector shapes into 3D features
- Zonal Statistics
- Raster value extraction
- Creating points from tabular data

Lauren McKenna

lmckenna@uw.edu, April 2016

University of Washington Tacoma, Geospatial Technologies

ArcMap 10.3.1, ArcScene 10.3.1

Projection: NAD 1983 HARN State Plane Washington South FIPS 4602 Feet