Adjusting a Grade

First, you should change the chart type from Line to XY Scatter so that length intervals are constant along the x axis.

Second, by what criteria would you grade?

Naively, you could add a first-order trendline. That would give a best-fit linear slope from one end to the other.

Or, you could join the start and end points with a line.

Or, you could create a shallower curve that joins the end points.

Or, you could use an algorithm to minimize the amount of dirt moved subject to having some maximum slope. There is surely on ocean of commercial software to do that.

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Change your title to something FDibbins likes, and I'll post a solution that matches the elevations and slopes at each end and moves no dirt beyond the boundary.

I think the OP has punted on the thread, but I found the problem interesting, so I'm posting this for Alf's perusal.