Background Information Methods Pre- Processing in ArcMap Processing in Fusion Analysis

Transcription

1 DETECTING RIPARIAN VEGETATION CHANGE USING LIDAR WILLIAM SERCOMBE ALEX THOMAS GEOG 593 PRESENTATION OVERVIEW Background Information Research Question Study Area Methods Pre- Processing in ArcMap Processing in Fusion Analysis Analysis in ArcMap Statistical Testing

2 RESEARCH QUESTION Can meaningful vegetation changes be derived between two LiDAR flight missions? H 0 : μ 1 = μ 2 H 1 : μ 1 μ 2 Where: μ 1 = vegetation height difference μ 2 = building height difference OUR OBJECTIVES Develop canopy height analysis workflow Learn and ArcMap canopy metric best practices Derive statistical products from LiDAR data Compare means / variation between samples using t-test

3 STUDY AREA Riparian Zone in Union County Grande Ronde River Basin Currently being assessed and managed by Bureau of Reclamation. DATA Catherine Creek (August th, 2009) Point Density: 7.23 points / m points / ft 2 Catherine Creek (September 29, 2011) Point Density: points / m points / ft 2 Factors to consider: Growth or effects of reclamation Seasonal change leaf on/leaf off Disparity in sampling density

4 ArcMap Fusion ArcMap Ortho- Photos Mosaic to New Grid Metrics.exe Canopy Model.exe Catherine Creek 2009 Catherine Creek 2011 LAS (Ground) Ortho- Photos LAS (Ground) LAS (All Points) Point File Info LAS to Multi Point LAS (All Points) Point File Info LAS to Multi Point Mosaic to New Point to Point to Import to Fusion Import to Fusion Canopy Height.exe Canopy Metrics.exe Canopy Metrics.exe Export Model Canopy Metrics.exe Export Model X3 X3 Import to ArcMap Import to ArcMap Building Image to Image Registrations SPSS Statistical Analysis Set Null Calculator (remove noise) Calculator (Minus) Feature Height Difference ORTHOPHOTO MOSAIC Mosaic to New Tool

5 DEM CONSTRUCTION LiDAR Classification Codes Point File Information Tool Source: Lidar Analysis in ArcGIS 10 for Forestry Applications DEM CONSTRUCTION (CONT D)

6 SOFTWARE LiDAR viewing and analysis software suite. Developed by US Forest Service at Pacific Northwest Research Station Uses a GUI for viewing data models and a command line interface for executing analysis functions. USING THE COMMAND LINE IN Must first add Fusion.exe to your PC s system environment variables in order to use its command line utilities. Batch files (.bat) are created in Notepad to execute operations, following a syntax specific to each utility. In this example, the canopymodel utility is used to generate a Canopy Height Model, by using the bare earth DEM to normalize the LAS point cloud.

7 WORKFLOW Create / load reference image Convert DEM to ASCII grid (.asc) in ArcMap Load LAS point clouds Import bare earth surface Convert ASCII grid to PLAN DTM format in Fusion Compute gridmetrics Create Canopy Surface Model Create Canopy Height Model Canopy Surface Model Export canopy models (TINs) into ASCII grid format Use ASCII to in ArcMap BUILDING FEATURE HEIGHT MODEL Point File Information (2011) LAS to Multi-Point LAS Class Code 6 (Buildings) Clip Floating Point Expression Point to Calculator (Minus DEM)

8 REMOVE BUILDINGS FROM CHM Convert Buildings to Polygon Buffer Polygon (4ft) Convert Polygon to Set null values to 0; non null 1 Set CHM to Null if Buildings = 0 BUILDING HEIGHT DIFFERENCE

9 BUILDING HEIGHT NOISE REMOVED CANOPY HEIGHT DIFFERENCE

10 RESULTS Export Height Models to SPSS to Point (buildings & canopy) Export to DBF Consolidate values into one column Run Independent Samples T-Test in SPSS RESULTS (CONT D) Failed to reject the null hypothesis. H 0 : μ 1 = μ 2 Not enough evidence to conclude that variation in vegetation heights is statistically significant.

11 LINKS USFS Remote Sensing Applications Center Lidar Training (includes Fusion Tutorial): Lidar Analysis in ArcGIS 10 for Forestry Applications