Geocalc And Rhumb Lines

[+fizzymagic]

I have been messing with GeoCalc recently. I have added the ability to do rhumb line calculations in addition to Vincenty and great circles.

 

A "rhumb line" is the path you would follow if you kept exactly the same heading along the entire course. So, if you were to start out at a heading of 48 degrees, and as you traveled you kept your heading at 48 degrees, you would be following a rhumb line. Sailors and pilots often use rhumb lines for navigation.

 

Contrary to the name, a rhumb line is a curved path. It's actually a spiral path that ends up at one of the poles eventually. To follow a rhumb line, you have to constantly correct your course to maintain the same heading. Rhumb lines look straight on a polar Mercator projection (not on UTM, though), so many people think of them as "straight" lines.

 

Is this a useful feature to add to the released version of GeoCalc? It's clear that there are a lot of people who are already pretty confused about geodesy and projections; do you think that adding this feature would increase or decrease the confusion?

 

Thanks for any advice!

[+fizzymagic]

If anyone wants to play with the new version, it is here.

 

Not guaranteed to be bug-free.

[+Cardinal Red]

Hi Fizzy

 

I don't think I NEED a Rhumb Line Calculator, but I found it interesting to study.

 

Open one "Window" of GeoCalc and populate the fields.

 

Open two more "Windows" of GeoCalc and they pop up auto populated to the same coords.

 

Set one to High Accuracy, another to Great Circle, and the last one to Rhumb Line.

 

Very interesting to see the differences on all three right there at one time.

 

But I am confused about exactly what High Accuracy represents. Great Circle is the shortest distance. Good. Rhumb Line is the longest distance. Expected.

High Accuracy is in between and agrees with this online Great Circle Calculator.

 

Why does someone elses GC calculator match your High Accuracy instead of your GC calculator?

 

As long as you've gone to all the trouble of writing the Rhumb Line code, I think you should keep it in.