Numerically obtained spatial patterning accuracy in units of average cell diameters at different positions in the tissue (symbols) and for different degrees of non-linearity (colours). (A–C) Readout close to the source, at ; (D–F) Readout far from the source, at . Morphogen production scenarios are identical to Figure 4: Production in a source domain with morphogen-secreting cells (A,D), with a morphogen influx from the source at the source boundary (B,E), and with a specified morphogen concentration at the source boundary (C,F). Very low (high) influxes or amplitudes lead to flat (steep) gradients at strong decay non-linearity, limiting the parameter range over which the positional error can be reliably determined for (B,C,E,F). In all panels, each data point represents the mean from 103 independent simulations, error bars represent standard errors.