Evan Gowan evangowan@gmail.com Tools to interpolate between contour polygons. I made this specifically to interpolate between ice sheet margin reconstructions in an objective matter. To use this, you need three GMT formatted text files: 1) Margin time step you are interpolating from (e.g. the margin of the ice sheet at its maximum extent) 2) Margin time step you are interpolating to (e.g. the margin of the ice sheet at present day) 3) A file with lines that point in the direction of interpolation When I first tried to implement this, I was not using the third file, but this will only work in the case where you are interpolating between one relatively simple polgyon to another relatively simple polygon. I encounter problems when you were interpolating to margins that include islands, and when there were relatively narrow fjords. To create the third file, I basically import the two margins in QGIS, and draw lines between them in the direction of retreat. If there are narrow fjords or islands, you need to have a high density of points between the margins. This requires a bit of refinement, so you have to import the flowline files that are generated by flowlines3 into QGIS to check. The assumption here is that the velocity of the interpolation will vary based on the distance between margins (1) and (2). This is of course not always a correct assumption, so it might be necessary to adjust the margin reconstruction manually. Maybe if I have time I could make it so it can incorporate actual chronlogical data, but I expect that will be very complicated. The scripts used to make the final contours use several programs from Generic Mapping Tools (GMT). I have been using GMT verion 5.x. Website: http://gmt.soest.hawaii.edu/ Some of the code in these programs is based on code and concepts that I wrote during my PHD, some of the details that can found in the following papers: Gowan, E.J., 2013. An assessment of the minimum timing of ice free conditions of the western Laurentide Ice Sheet. Quaternary Science Reviews, 75, pp.100-113. Gowan, E.J., Tregoning, P., Purcell, A., Lea, J., Fransner, O.J., Noormets, R. and Dowdeswell, J.A., 2016. ICESHEET 1.0: a program to produce paleo-ice sheet reconstructions with minimal assumptions. Geoscientific Model Development, 9(5), pp.1673-1682.