Tornados, USA
Tornado Touchdowns and Paths in the Continental USA, 1950-1995
Elise Bowditch © 2001
Data sources:
"Tornadoes by state/territories 1950-1995" at http://www.spc.noaa.gov/archive/tornadoes/
Data Preparation:
- read the data into Access database from text files available on website
- adjusted the latitude & longitude decimal numbers
- split data into touchdowns (one point) and paths (2+ points)
- adjusted the path data so that it was a series of records each containing one point
- some data corrected by hand (bad segment numbers)
- exported using macroExpress / Access
Methods:
Software used:
Data preparation: Access and MacroExpress
Map creation: ArcView 3.2a
Animation: Adobe Photoshop, QuickTime via QuickMovie
Steps:
- import and process data using a combination of macroExpress scripts and Avenue scripts
- add table to ArcView
- add table as event theme in the view
- use XTools to create a polyline from points in the event theme
- join the event theme table with polyline theme (to preserve fscale in line)
- merge polyline themes for a specific month/year into one theme for that month/year
- (if only one polyline theme for a month/year, save theme with joined tables as another shapefile, to preserve fscale)
- create event theme/shapefile for touchdowns for given month/years
- use avenue to export layout files for each month year