On the large scale, you get pretty much the same map whether you're calculating 'to' the marker or 'from' the marker. The only exception is if you plan on commu

On the large scale, you get pretty much the same map whether you're calculating 'to' the marker or 'from' the marker. The only exception is if you plan on commuting in the opposite direction of rush hour traffic, both ways. i.e., if you think about commuting to work in the morning, the heatmap will show you the times it takes to drive from any given location to the marker. If you're thinking about driving home in the evening, you can think of the time from the marker to any given location. on the macro scale, most streets aren't one-way, and commute times tend to be symmetric.