I have a couple different types of bathymetry data for different timelines. I'm trying to calculate a couple things. First doing a subtract differential between rasters to determine depth change. I'm running into a problem with converting the polygons making up the bathymetry into contours or comparable DEM for comparison? I can't use topo to raster or polygon to polylines and get the correct attributes assigned to new polylines? What can I use to convert the polygons?