The computation of the DFHRS databases for NN- and for nomal heights, respectively were done
in cooperation between Ingenieurbüro Seiler
The quality of DFRHS database Nordrhein-Westfalen is again 1cm. The fig. below shows the isolines of the HRS N(B,L), computed with DFHRS-software version according to the approach stage 1, formulas (2a-f).