Trying to figure out how to get the curve I want, to plot on a map. This was my first iteration: It's wrong. The following sample will illuminate why. For illustration, the sample is much smaller and far more idealized than my real dataset, which is 100+ datapoints. In my idealized trip, I've driven a course 10km long and taken odometer readings every minute. (The course is 2 km on a back road, followed by 8km on a highway. The 2km on the back road took me 8 minutes, while the 8km by highway took me only 2 minutes.) So, I dump all these odometer readings into Excel, and it allows me to produce the Distance / Time graph, but I can also produce the Speed / Time graph. I took speed the graph itself and superimposed it onto the map, twisting it to match the course. You can see that is is completely wrong. The leg of the journey from B to C,where I am travellnig at 4km/minute is 4/5ths of the entire course, but the overlay indicates that it is only 1/5th. I know why it's wrong, what I'm trying figure out is how can I transform the datapoints in Excel so that the speed graph is correct. I'm thinking I have to change the cell formulae to calculate speed per cumulative distance travelled? I'm not sure.