10 metre uncertainty band PPRi de Châlons-en-Champagne — CAC sector

The studies carried out in the context of the development of the PPRi de Châlons-en-Champagne (map of hazards) were carried out on the scale of 1/10 000th, and mapped on a background IGN scan25 enlarged to 1/10 000th. Since regulatory zoning stems from the intersection of the hazard map and the stake map, the accuracy of this mapping cannot be greater than that of the hazards. Consequently, the scale of use of the regulatory zoning is that of 1/10 000 and exploitation on a smaller cadastral scale (1/5000 or 1/2000) is not recommended. However, municipalities wishing to do so may transpose the regulatory map into their planning documents provided that they comply with operating principles in order to take account of the uncertainty associated with the expansion of the zoning, particularly at the boundary of the area. Indeed, it is not possible to improve the accuracy of the initial data which presents uncertainty about its contours of the order of 10 metres, which is relatively important on the scale of a plot in an urbanised area. The transposition of the regulatory map into a cadastral planning document cannot therefore be limited to a mere enlargement, which would result in a false precision of the contours. Therefore, a guide defines the principles that would allow municipalities who wish to do so, a transposition into an urban planning document (PLU, municipal map) taking into account the uncertainties between each area. It must also make it possible to define the area regulation to be applied when considering planning permissions. Genealogy: The limits of the uncertainty band are not represented on the PPRi graphic documents, they are not official in nature. The boundaries of the uncertainty band are represented by a polygon straddling the separation between two zones of the regulatory Zonage, its width is 10 metres and it follows neither cadastral nor administrative boundaries. A guide to the interpretation of this band sets out the principles for its operation.本研究围绕夏龙-昂-香槟风险防控规划（PPRi，风险地图）的编制展开，制图比例尺为1:10000，底图采用放大至1:10000的法国国家地理研究院（IGN）25比例尺扫描图。由于管控区划由风险地图与承险对象地图叠加生成，其制图精度不得高于风险地图本身。因此，管控区划的适用比例尺为1:10000，不建议采用更小的地籍比例尺（如1:5000或1:2000）开展应用。若地方市政部门有此需求，可在遵循相关操作原则的前提下，将管控地图纳入其规划文件，同时需充分考虑区划边界扩张带来的不确定性，尤其是区域边界处的不确定性。 初始数据的轮廓存在约10米的不确定性，且无法通过后续处理提升其精度，这在城市化区域的地块尺度下影响相对显著。 因此，将管控地图直接转绘至地籍规划文件中并不可取——单纯的尺寸放大会导致轮廓精度失真。为此，一份专项指南明确了相关操作原则，允许有需求的地方市政部门将管控区划转绘至城市规划文件（如地方城市规划方案PLU、市政规划图），同时兼顾各管控区间的不确定性。该指南还需明确，在审批规划许可时应如何界定适用的管控区域。 溯源说明：不确定性带的边界并未在PPRi的图形文档中体现，且不具备官方效力。不确定性带的边界由跨越管控区划两个区域的多边形表示，带宽为10米，既不遵循地籍边界也不遵循行政边界。另有一份解读指南阐明了该不确定性带的应用规则。