As you may know, some of the data that we used didn’t have coordinates. Thomas P. Grazulis’ Significant Tornadoes, for example, only gave relative locations and directions, not absolute coordinates. Therefore, we had to manually compile all of these tornadoes–1,949 as of now, with more coming eventually. In the interest of assuring confidence in the dataset, here are the instructions the content team used for converting the text descriptions given in Grazulis’ book to actual coordinates, lightly edited for clarity:
1) Download Google Earth Pro: https://www.google.com/earth/versions/#download-pro
2) In Google Earth Pro go to Tools->Options->3D View and set Show Lat/Long to Decimal Degrees
3) Find the first F2 in your decade in the Grazulis book. The Grazulis entry formatting is listed on page 16 of the pdf (page vii in the book)
4) Enter the given date into the spreadsheet
5) Enter all states the tornado passes through. The first column will always have a state in it, the 2nd and 3rd columns are by default null (-9999), but if the tornado passes through 2 or 3 states then replace the -9999 with those states.
6) Next you need to find the path. Basically, you should start the path by finding the first given distance from a city (say 10 miles north of Omaha), then if there are more relative locations with distances, holding your finger where the last point was to keep track of it, and starting a new measurement at the next location. For any further ones, just keeping track of the initial one is sufficient, as long as you make sure the tornado track passes near the point you found from the 2nd town. It’s impossible to be more precise anyway. Then check that the path passes by towns without given distances in the correct manner/direction (e.g. making sure that if the book says “NW of Garden City,” then the track passes NW of Garden City). Once the path is complete relative to the given cities, you then should compare both the given length and the given motion (For example a given motion ENE). If necessary, extend the tornado length from the front and back while preserving direction to align closer to the given path length. Last but not least, compare the given county(ies) and make sure the tornado passes through all and no more. If everything checks out then your path is solid.
Possible Issues:
– If a given city doesn’t exist on Google Earth, you can google “City, County, State” and see if it shows up on wikipedia or somewhere else where you can copy and paste coordinates to use as the location. If not, then use other given cities, direction, and counties to figure out the path to the best of your ability.
– If the path length, given counties, or given cities do not match, first see if any given cities are in a county not listed, and google “given city, county, state” to see if there are 2 locations with the same name. If not, always prioritize your path based on this hierarchy and make a note in the Notes column of the spreadsheet, located at the far right
1. towns hit (make sure to have the path go through or near these)
2. start/end location (e.g. 7 miles W of Wichita KS)
3. vicinity to towns near path
4. counties affected
5. similarity to path length from Grazulis
-If only 1 point of reference and no path length or motion is given, set start and end points to be the same.
9) Hover over the start point of the measurement tool, and enter the lat and long into the doc (lat/lon found in lower right corner). Do the same with the end point.
10) Add the local standard time (include a colon!), F-scale (CAN BE 1 OR UNKNOWN IN RARE INSTANCES, AS THE BOOK INCLUDES FATAL NON-SIG TORNADOES, MAKE SURE NOT TO SKIP F1s AND FUs), fatalities (if it says people may have died, don’t count them, only use the number in the header), injuries, and the path width. If any information is unknown, enter “-9999”
11) Repeat steps 4-10 for each tornado