计算两点之间的距离 - Java

Question

I have inherited a code and it has this small function written to calculate distance between two points.I'm wondering , what it does. I know the lat long data is in decimal degrees. Could anyone please throw some insights, if this calculation is right?

     private double calculateDistance(QuoteItem quoteItem, RouteInfo routeInfo) {
        final double distance =
           ((Math.max(routeInfo.getLatitude(), quoteItem.getLatitude()) - Math.min    (routeInfo.getLatitude(), quoteItem.getLatitude())) +
           (Math.max(routeInfo.getLongitude(), quoteItem.getLongitude()) - Math.min(routeInfo.getLongitude(), quoteItem.getLongitude()))) * 60.0;
return distance;
     }

Answer 1

This is a variant of the Manhattan distance calculation where it's not a true Euclidean hypotenuse distance calculation, but rather a simple sum of the two sides of the right triangle multiplied by some multiplier, 60. I usually see it written more simply as

Math.abs(p1.x - p2.x) + Math.abs(p1.y - p2.y)

Which is essentially what your calculation is, except you're also multiplying it by some scaling factor, 60.0.

I've used this in programs where I want to get a quick and dirty estimate of distance with an emphasis on quick since it involves no square roots. For instance, I used it once for very rough (and incorrect but correct enough for the purposes) calculation of the differences between pixel colors, where I had to make this calculation repeatedly for the pixels contained two images, in real time, and where need for speed trumped the need for accuracy.