Juneau Nature

Natural & cultural history of Juneau & Southeast Alaska

Juneau Nature - Natural & cultural history of Juneau & Southeast Alaska

IfSAR: the Southeast ‘big-picture’

The long-awaited IfSAR, October, 2015

IfSAR stands for interferometric synthetic aperture radar. While many scientists, naturalists and outdoorspeople in Juneau have now heard of LiDAR—because of the extraordinarily detailed topographic detail and forest structure maps it’s given us in the CBJ—fewer know about a slightly lower resolution dataset that was acquired throughout the state between 2010 and 2014, and has finally been processed and delivered. It can be downloaded from the GINA website. Because I wanted the entire collection for Southeast Alaska, I’ve bypassed the download process and copied a drive prepared by Dustin Wittwer, USFS, cataloging all of the IfSAR output south of Yakutat.

The Alaskan IfSAR project consists of 3 basic products, from which many others can be spun off in GIS: bare-earth DEM (DTM, or digital terrain model), Surface DEM (DSM or digital surface model), and an orthorectified radar intensity image (ORI). The elevation models have a 5-m post spacing, 22-ft contour accuracy, 3-m vertical accuracy and 12.2-m horizontal accuracy.

As a landforms enthusiast, I’ve been enthralled by Juneau’s LiDAR bare-earth display for the past 2 years. In fact, it’s spoiled me to the degree that consulting or teaching gigs in other parts of Southeast have begun to feel cartographically impaired. So the sudden delivery of the IfSAR DEMs for almost the entire archipelago is like Christmas 2 months early! Thank you, GINA and Dustin, and Dave Gregovich at ADF&G for your pioneering analysis of this dataset.

landforms traced onto IfSAR bare-earth

landforms traced onto IfSAR bare-earth