Dataset Direct Download Service (WFS): DDT 70- Isocotes of PPRI n°20080026 Saône Basse Vallée

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的等洪高线（isocote）是针对参考洪水计算所得的洪水高程值，该高程值采用NGF 69基准面下的Z值标注。遵循PPRI规程中规定的建筑施工规则与需遵守的技术建议，等洪高线可用于计算经许可的建筑安装作业所需观测的最高水位高程。该高度的计算公式如下：Z = (a·z₂ + b·Z₁)/(a+b)，其中Z₁为最邻近的高值等洪高线，Z₂为最邻近的低值等洪高线，a为Z点与Z₁等洪高线间垂直于等洪高线走向的距离，b为Z点与Z₂等洪高线间垂直于等洪高线走向的距离。PPRI汇报说明文档的附录中通常配有示意图，以直观阐释该公式。