I was listening to a recent guest on your Cool Tools podcast [It was Nik Schulz – MF] that was an “overland” enthusiast and one of his recommendations was a map measuring tools called an opisometer. While my day job as a design engineer exposes me to some Cool Tools, I’ve been a car rally navigator / co-driver for decades. While there are few time-speed-distance map rallies anymore, a common feature is the need to measure distances on a map quickly, while preparing your map at the beginning of the event. While a classic mechanical opisometer is a precise tool for distance measurement on a map, it is slow and needs to be scaled much in the same way a slide-rule is a precise calculator, but its day has passed.
For messing distances on a map or other curvy 2-D path, I’d suggest a digital map scale like the Scalex map wheel ($49). You calibrate the tool by rolling it over the scale of distance on a map or entering the scale factor directly, and then roll the wheel along the path you want to measure and it reads out digitally.
The precision is adequate for resolving distances to corners on a night rally in a February snowstorm. It’s one of the tools that I keep in my navigator’s bag for map rallies. If this interests you and you want to know how to read the rest of the map while bouncing around in the car at night, we’ll, there’s a cool tool for that also.
— Marc Goldfarb
Scalex MapWheel Measure ($49)
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