BEDMAP1 - Ice thickness, bed and surface elevation for Antarctica - standardised shapefiles and geopackages

All non-value data were converted to -9999, including any negative ice thickness values and any points with clear outliers. We checked the minimum and maximum values of each field to ensure the data are in a reasonable range and calculated mean and standard deviation on each dataset to identify potential issues. For example, if longitude/latitude values did not fall within the expected -180 to 180 or -50 to -90 degrees range respectively, the entire row was removed. When no ice thickness values were provided but surface and bed elevation values existed, we simply calculated ice thickness by subtracting the surface value from the bed value. At times, bed elevation was higher than surface elevation, likely due to issues with the semi-automatic picker used to extract the surface and bed reflector or a lack of distinctive reflectors in areas of shallow ice. To prevent this affecting the gridded product, we converted these values to -9999 for both the surface and the bed. Finally, we also conducted routine checks on the ice thickness data by comparing the given ice thickness value with the inferred ice thickness calculated from subtracting surface with bed. If these did not match, we placed -9999 on the ice thickness values.

所有非有效数据均被统一转换为-9999，涵盖所有负冰厚（ice thickness）值以及存在明显异常值（outliers）的测点。我们对每个字段的最小值与最大值开展校验，以确保数据处于合理区间；同时针对各数据集计算均值与标准差（standard deviation），排查潜在的数据质量问题。举例而言，若经纬度（longitude/latitude）未分别落入预期的-180°至180°与-50°至-90°范围，则将整行数据移除。当未提供冰厚数据但存在表面高程（surface elevation）与冰床高程（bed elevation）时，我们通过冰床高程减去表面高程的方式直接推算冰厚。冰床高程高于表面高程的情况时有发生，这可能是由于用于提取表面与冰床反射层的半自动拾取器（semi-automatic picker）存在缺陷，或是浅冰区域缺乏辨识度较高的反射层所致。为避免此类问题影响网格化产品（gridded product）的最终质量，我们将该情况下的表面高程与冰床高程值均转换为-9999。最后，我们还针对冰厚数据开展了常规校验：将给定的冰厚值与通过表面高程减去冰床高程得到的推算冰厚进行比对，若二者不匹配，则将该冰厚值置为-9999。