Hi, (sending again, as I forgot to CC the mailing list in my reply)

I am trying to make sense of the error message I get when trying to plot using kwant.plotter map(). The error message is "the reference distance a is too small", and a is the lattice spacing. What is the meaning of this error message?

I believe that this can happen when your system is too big compared to the reference distance (which defaults to the typical hopping length). In such a case interpolation may be confusing, as a single pixel in the output image effectively covers several sites. Concretely the check that is made is a < 1E-6 * np.linalg.norm(cmax - cmin) where `cmax` and `cmin` are the largest and smallest (in some suitable sense) site positions in the system (i.e. they define the bounding box) You should probably have a second look at what it is that you are trying to plot, to see if it is sane. If it is, then you can set the reference length explicitly (it is the `a` parameter to `kwant.plotter.map`) so that it covers several sites (although if your plotted quantity does not vary sufficiently smoothly between sites, the colorplot will not really be very useful) Hope that helps, Joe