AlphaEarth 能区分城市却压缩城市内部差异
原标题：AlphaEarth distinguishes cities but compresses urban variation
AI 摘要
该研究审计了卫星基础模型 AlphaEarth 的城市表征，覆盖 162 个国家 1000 个城市区域。研究发现城市在超球面上占据偏移但重叠的区域，距全球均值方向 62.7°，大陆与气候可解释 24.3% 的城市中心均值方向差异；城市内部城市化程度仅承载 8.9% 的变化，且保留的变化方向随地点变化而非单一轴。研究还发现表征差异不平等：城市中心离散度随国家发展水平每标准差增加 14.1%，控制植被与纹理对比后最多剩 6.4%；年度表征移动量约为重绘像素解释量的近八倍，并受 2022 年 Sentinel-1B 失效影响。结论是 AlphaEarth 支持跨区域比较，但其年度层间差异尚未验证可用于时间比较。
正文节选
AlphaEarth distinguishes cities but compresses urban variation Abstract Cities differ in built form, land cover and development history, complicating comparison across places and time. Satellite foundation models map Earth’s surface onto common numerical representations. Yet the tasks and targets used to shape them typically do not focus on cities: globally consistent labels for urban function do not exist, and many datasets—especially land cover and land use classifications—collapse the built e