Storm Tracking

Since I live on the South Carolina coast I have great interest in tracking hurricanes as they threaten my coast. For years I have uses Microsoft’s Streets and Trips for that purpose, but even though I still have a working copy, I know its days are numbered, and I have been looking for a replacement. I have been messing around with routes on the DS-86, and there it is.

The solution is to create a “Reverse Route” that is updated as the official storm locations are published.

The requirements are:
1. The unit Base Map showing the whole world.
2. The unit has a “Straight Line” or “Off Road” navigation mode.
3. The unit allows editing a route.

I know that the DriveSmart 61, 65, and 86 meet those requirements and suspect many more do also.

How to Do It on the DS 86
1. Set navigation mode to “Straight Line.”
2. Choose “Where to”, select “Coordinates” and enter the initial location of the storm center. Then select “Go.”

You will see the distance to the storm center in the “Distance to Next Turn” panel.

If you enlarge the map, you will see the Lat/Lon plot of the current storm center, a line from the current location to the storm center, and a visual bearing to that location.

HERE’S THE TRICK
When the next storm plot comes in:
1. Select “Where to.”
2. Select “Coordinates.”
3. Enter the Lat/Lon coordinate.
4. When prompted where to put it, select “Next Stop.”
5. Select “Go.”

Now the course line and “Next Stop/Next Turn” info refers to the current plot. As you continue doing this routine, you will have a track of the storm from where you started making the tract until you stop with info about the latest position. Note that the distance and visual heading is from the current location, and if you move, the current distance and heading will move with you.

At any point in the process, you can save the route and recall it when needed. This not only allows you to use the GPS for normal functions while preserving the current storm track, but tracking multiple storms as they occur, and we have had the need to tack multiple storms lately.

Mariners may be interested to know that it seems that straight line distances on the DriveSmart units are “Great Circle” distances. This has not been verified by Garmin. The Garmin Support people don’t seem to know what a great circle is.

For those that don’t know, but are interested, a Great Circle on the earth surface is a circle with its center at the center of the earth. An arc on that circle connecting two points is the closest distance between them. Except for true north/south routes and an east/route at the equator, the heading between the two points on the great circle route is constantly changing. That is why it takes special map projections to display them as straight lines.