Dataset Direct Download Service (WFS): DDT 70- Isocotes du PPRI n°20120002 Saône Amont

The isocotes of the PPRI are the altimeter values (Z in the NGF 69 marker) of the flood heights calculated for the reference flood. Subject to the rules for constructions and the recommendations to be observed, laid down in the regulation of the PPRI, isocotes make it possible to calculate the altimetry of the highest waters which should be observed for the installation of an authorised construction. This height is calculated as follows: Z = (a * z2 + b * Z1)/(a+b) with Z1 = nearest isocot of highest value, Z2 = closest isocot of the lowest value, a = distance between the Z point and the Z1 isocot measured perpendicular to the isocot route, B = distance between the Z-point and Z2 isocot, measured perpendicular to the isocot route. A schematic generally makes this formula explicit in the appendix to the PPRI presentation note.PPRI的等水位高程线（isocotes）为参考洪水工况下计算得到的洪水高程值，其高程标记采用NGF 69基准（记为Z）。依据PPRI法规中规定的工程建设规则与应遵循的相关建议，等水位高程线可用于计算经许可的建设工程施工时应观测的最高洪水水位高程。 该高程的计算公式如下： Z = (a·Z₂ + b·Z₁)/(a+b) 其中，Z₁为数值最高的相邻等水位高程线，Z₂为数值最低的相邻等水位高程线，a为待求Z点与Z₁等水位高程线沿等水位线走向垂直方向测得的距离，b为待求Z点与Z₂等水位高程线沿等水位线走向垂直方向测得的距离。 PPRI说明文件的附录中通常配有示意图，以清晰阐释该计算公式。