Land-sea boundary — Finistère department

The Land-Sea Limit is the astronomical high seas lead (PHMA) in the case of a 120 tide and under normal weather conditions (no wide wind and average atmospheric pressure of 1 013 hPa). The achievement of this geometric line is naturally defined as the intersection of a model of PHMA (extended to the coast and the estuaries) based on the available Bathyelli surfaces, and a numerical model of high-resolution coastal terrain. This limit, which also corresponds to the upper limit of the shoreline by materialising the top of the foreshore, takes into account, where they exist, the three administrative maritime boundaries: the Transverse Sea Limit (MCL), the Water Salt Limit (LSE) and the Maritime Affairs Limit (MAL). This limit is measured (rated) in relation to local hydrographic zeros as well as from altitude zero (IGN69 and IGN78 in Corsica). Attachment to other references (medium level, ellipsoid) is known. The Earth-Sea Limit product, derived mainly from the exploitation of the two products Litto3D®/RGEALTI® and Bathyelli, represents, at a metric resolution (1 to 5 metres), this theoretical entity by a set of 2D polylines describing the nature of the coast (artificial or natural, rocky or sandy, steep or low, etc.). The method of constructing the Land-Sea Limit allows the production of a continuous, homogeneous and spatially coherent boundary throughout the French metropolitan coastline. Use: In its planimetric dimension, the Earth-Sea Limit product is designed for analog use from the 1:2 000 scale; but it is imperative to consult the POSACC attribute (planimetric uncertainty) before any use on a very large scale. In its altimeter dimension, the user’s attention is drawn to the imperative need to consult the attribute VERACC (altimeter uncertainty combining the uncertainties of the MNT and PHMA). However, as the knowledge of PHMA is not exhaustive throughout the territory (i.e. rivers, lagoons, etc.), the 3 maritime administrative boundaries are identified (the “limarc” attribute at the passage of the Land-sea Limit) and used for closures. Attention, certain administrative maritime boundaries, although defined by decrees, present planimetric uncertainties of several hundred meters (commented in the attribute “descrp”). The product specification Land-sea limit also details the parties involved in the administrative maritime boundaries. The Land-Sea Limit is not intended to be used on scales higher than indicated. The Land-Sea Limit has not been designed to develop or inform indicators of coastal artificialisation; other approaches are taken within the framework of the Marine Strategy Framework Directive. However, due to its design identifying the natural and the artificial limit, it can contribute effectively to the result of completeness in this area. The Land-Sea Limit has not been designed for use in the operation of nuclear installations, air navigation or communication systems, air traffic control or navigation systems or any other area referred to as ‘dangerous activities’, where a product failure could result in death, bodily harm or serious physical or environmental damage. ©Shom-IGN Update: October 2021 This earth-sea limit replaces the coastline “HISTOLITT®” N_TCH_029 © IGN/SHOM 2009陆海界限（Land-Sea Limit）指在120潮位、无强风且平均大气压为1013百帕的正常气象条件下的天文公海潮位基准（PHMA）。 该几何界线的定义本质为：基于现有测深椭球（Bathyelli）海面构建的PHMA模型（延伸至海岸与河口区域）与高分辨率海岸地形数值模型的交线。 该界线通过表征潮间带（前滨）的顶部，对应岸线的上限；若存在相关行政海事边界，将纳入考量范围，包括横向海界（Transverse Sea Limit, MCL）、水盐界限（Water Salt Limit, LSE）以及海事事务界限（Maritime Affairs Limit, MAL）三类。 该界线以当地水文基准面为基准进行量测，亦可关联至海拔零点（科西嘉岛采用IGN69与IGN78基准），同时支持关联至其他基准（如中等高程基准、椭球面基准）。 陆海界限产品主要依托Litto3D®/RGEALTI®与测深椭球（Bathyelli）两款产品的解译应用生成，以1至5米的米级分辨率，通过一系列二维多段线表征该理论界线，并描述海岸属性（人工或自然、岩质或沙质、陡峭或平缓等）。 陆海界限的构建方法可实现法国本土海岸线全域连续、均质且空间一致的边界产出。 应用说明： （1）平面维度下，陆海界限产品适用于1:2000比例尺及以上的模拟制图使用；但在超大比例尺场景中使用前，务必查阅POSACC属性（平面位置不确定性）。 （2）高程维度下，用户需务必查阅VERACC属性——该属性表征融合了数字地形模型（MNT）与PHMA不确定性的高程不确定性。 （3）然而，由于PHMA在全域（如河流、潟湖等区域）的覆盖尚不全面，需通过陆海界限处的"limarc"属性识别三类行政海事边界并用于边界闭合。需注意：部分行政海事边界虽经法令明确，但平面位置不确定性可达数百米，相关说明可查阅"descrp"属性。陆海界限产品说明书亦详述了行政海事边界的涉事主体。 （4）陆海界限不得在高于标注比例尺的场景中使用。 （5）陆海界限未用于开发或表征海岸人工化指标，相关研究需依托《海洋战略框架指令》框架下的其他方法开展；但由于其可区分自然与人工界线，仍可有效助力该领域的完整性评估结果。 （6）陆海界限未针对核设施运行、航空导航与通信系统、空中交通管制或导航系统，以及其他任何可能因产品失效导致人员死亡、身体伤害或严重物理/环境损害的"危险活动"领域设计。 ©法国海道测量局-法国国家地理与林业研究院（SHOM-IGN） 更新时间：2021年10月 本陆海界限替代了2009年版权归IGN/SHOM所有的海岸界线"HISTOLITT®" N_TCH_029。