Evidence before visualisation先核验，再可视化

CURRENT LIMITS / 当前限制

What the map does not claim

• CMAB 2.0 · 2013 multi-attribute buildings: Source: CMAB2算法改进版数据20130111.geojson, with the same supplied CMAB field dictionary. The 2013 edition has 473,430 source records and 473,014 displayable polygons; 416 degenerate/no-area records are excluded only from display. Both editions use matching categorical colours and independently computed numeric rank quintiles: the same rank colour is not the same absolute value across years. Current online basemaps are not historical 2013 imagery.

  2013版原始文件和字段字典私有保留；473,430条源记录、473,014个可绘制面，416条无有效面或精度退化记录不绘制，原件不删除。十项属性和2023版一致，结构中额外保留木结构类别；demolished只表示历史期未关联现代期建筑，不等于确认拆除。两期均默认关闭，可单独开启或叠加排序。数值五分位各自在本期有效值中计算，相同分档颜色不能直接解释为相同高度/质量或跨期变化；请对照弹窗原始指标。Age=0、M和空演化编码单列，结构/风格/质量及演化仍为候选。源声明CRS84，标准Mercator显示；沿用相同的几何修复、孔洞保护、多级概览和共享精细几何方法。20130111只是文件版本标签，非已核实调查日；现代底图不能用来证明2013年的建筑是否存在。

• CMAB 2.0 · 2023 multi-attribute buildings: Source: CMAB2算法改进版数据20230701.geojson and its supplied field dictionary. The filename date is a version label, not a verified survey date. Ten selectable attributes share geometry; numeric fields use five equal-count rank bands with stable source-order ties, while categorical fields keep their source categories. Special codes are shown separately, not as low values. The source declares CRS84; the derived display uses standard Web Mercator.

  CMAB 2.0 · 2023：459,232条源记录，458,843个可绘制建筑面；389条无有效面或数值退化记录不绘制，原件保留。按功能、高度、参考年代编码、候选质量、结构、风格、跨期状态、关系类型、演化候选及复核状态切换。高度单位“米”来自随附字段说明；Age为参考年代或编码，0含义未说明。Quality的M、Structure/Style的M及空演化标签单独显示灰色；数值0保留。数值字段按有效数值等数量五分位，同值按源顺序稳定分配，不以阈值重新推断档次。Quality颜色深仅表示数值较大，不宣称质量更好。constructed不等于确认新建；重建、分裂、合并、布局变化均为规则候选，需影像核验。内部building_id不在公开提示中显示。原始数据及字段说明私下留存；浏览副本修复可修复拓扑，不能形成有效面的条目排除并审计。默认关闭；概览瓦片按属性按需加载，近景共享几何，点击按面与孔洞精确查询。未取得权威六环界线，不额外裁掉来源范围；默认地图范围保持原六环建筑范围。各类候选属性不可用于安全鉴定。

• Building function change (2022–2025): 19,545 valid MultiPolygons, with the supplied CRS84 longitude/latitude coordinates transformed to standard Web Mercator. Six observed transitions between residential-dominant, office-dominant and other-dominant use categorical colours, not quantiles. Source fields are 22年主导功能 and 25年主导功能. Only changed buildings are included; no citywide change rate, causal explanation or survey accuracy is claimed. Names, classification method and licence are not supplied. “Other” does not imply vacancy or demolition.

  建筑功能变化：19,545 个有效多面，保留内部孔洞，源文件明确为 CRS84 经纬度，展示转为标准 Web Mercator。居住、办公、其他主导之间六种实际转变采用类别配色，不套用五分位。只有变化建筑样本，不能推断全市变化比例；未提供名称、分类方法、精度和许可说明。“其他”不等于空置或拆除。默认关闭；低级别轻量栅格预览，近景按视野读取精细多边形，点击始终用真实面（含孔洞）命中判断。

• Community quality: five colours are deterministic within-dataset equal-count rank quintiles, not externally validated or official quality grades; ties are split by source ID.
• Street spatial disorder: five colours are equal-count rank quintiles of the supplied relative score; ties are split by source FID. Source units, method and measurement date are not documented.
• Vacancy: HVR is retained as a 0–1 source ratio and assigned to five equal-count rank bands, including zero values; supplied names are shown where non-empty and automatically labelled only at close zoom, but the source does not provide a year, denominator, method or official vacancy standard.
• Height: building integers are preserved as raw values and assigned to five equal-count rank bands; no unit, floors or official measured height is claimed.
• Remainders: when a dataset size is not divisible by five, class counts differ by at most one feature; this is the mathematically balanced result.
• Community metadata: the supplied files do not document score/vacancy methodology, denominator, measurement date or licence.
• Boundary: the six-ring boundary is not included as an authoritative companion file yet.
• Publication: derived browsing tiles are served to make the map work; complete raw GeoJSON sources are not offered as public downloads.

ONLINE BASEMAPS / 在线底图

Three selectable providers

The map defaults to Esri World Imagery, with OpenFreeMap Positron (light) and OpenFreeMap Dark (dark) as alternatives. The two open-source styles are rendered by MapLibre. All three providers and the visibility switch are grouped in the top BASEMAPS panel; basemaps do not participate in thematic layer ordering or feature queries. Selecting a provider automatically restores visibility. The visibility checkbox hides or restores the current provider without changing it.

默认底图为 Esri World Imagery 高精度遥感，可切换 OpenFreeMap Positron 浅灰开源底图或 OpenFreeMap Dark 深灰开源底图。三个底图与显示开关统一位于右侧顶部 BASEMAPS 面板，不参与专题层排序或要素查询。选择底图会自动恢复显示；显示开关只负责隐藏或恢复当前底图，不改变选择。原 Esri 浅灰参考底图已移除。

Only the visible view is requested; Beijing Data does not mirror or bulk-download external basemap tiles. Availability and detail vary by provider, place and date, with no uniform resolution claim. Each provider's attribution remains visible. If an online service is unavailable, the independently hosted thematic layers remain usable.

仅按当前视野请求在线底图，不镜像或批量下载第三方瓦片。细节及可用性因服务、地点和年代而异，不宣称统一分辨率，并保留对应署名。若底图服务暂时不可用，本站独立托管的专题图层仍可使用。

OpenFreeMap / 官方说明 · OpenFreeMap styles and license / 样式与许可 · OpenStreetMap copyright / 版权

COORDINATES / 坐标

One display projection

The thematic layers and online basemaps are displayed in standard Web Mercator, with the same scale in both directions. Zooming, panning, location and feature queries use the same conversion. Coordinates are preserved from the supplied sources; this display alignment does not establish survey accuracy or remove differences in the dates and coverage of third-party maps.

专题图层与在线底图统一采用标准 Web Mercator 显示，横纵比例一致；缩放、平移、定位和要素查询使用同一套坐标转换。坐标来自用户提供的数据；显示对齐不等于测绘精度认证，也不消除第三方底图年代和覆盖范围的差异。街道数据未声明坐标系，当前经纬度解释仍按上方来源说明保留。

INTERACTION / 交互

Independent layers, precise queries

Use one finger to pan and two fingers to zoom around their midpoint. Feature queries follow the current layer order and continue to lower layers when the upper polygon is not hit. Street queries also work in the preview view. A dataset request failure is isolated to that layer; turn the affected layer off and on to retry. Unstarted requests for hidden CMAB/function-change layers are discarded, while completed tiles remain cached.

手机可单指拖动、双指围绕中心缩放。点击按当前叠放顺序查询，上层多边形未命中时继续检查下层；街道概览也支持点查。单个数据索引失败不影响其他图层，关闭再打开对应图层可重试。关闭 CMAB 或功能变化层会取消尚未开始的请求，已加载瓦片保留缓存；这不改变原始数据、坐标或分档。

MOBILE / 手机浏览

Keep the map within reach

On phones, use “Open map” to skip the introduction and “Layers” beside the map to open the existing basemap and layer controls. Close the panel to return to the same view. The map fits the available screen height without stretching coordinates; reset fits the full Sixth Ring source extent. Touch feature information has a close button, and longer attribute lists can scroll.

手机可用“直接查看地图”跳过介绍，点击地图旁的“图层”打开底图、图层与着色属性控制，完成后返回原视图。画布按可用屏幕高度调整，不拉伸坐标；复位时完整容纳六环源数据范围。触摸查询弹窗可明确关闭，较长属性可在弹窗内滚动；在地图外滑动可继续浏览页面。

CROSS-YEAR COMPARISON / 跨期对比

CMAB 2.0 · 2013–2023 building-change candidates

This derived view filters the two CMAB edition labels into four candidate classes: unlinked 2023 observations, unlinked 2013 observations, one-to-one form-change candidates and group-reconfiguration candidates. Explicit 1t1_stable and blank/undetermined evolution records are hidden. At detailed zoom, the layer reuses the audited source-edition geometry tiles; overview tiles are recoloured from their prebuilt status/evolution rasters, avoiding a second copy of all building geometries.

该派生视图按两期 CMAB 版本中的跨期工作标签，显示四类候选：2023版未关联观测、2013版未关联观测、一对一形态变化和组团重组。明确的“稳定”及空白/未判定演化记录不显示。近景直接复用已审计的两期建筑几何瓦片；概览从原有状态/演化栅格重分类，避免重复存储整套建筑几何。

No relation-index table with group_id/partner_ids was supplied. Therefore the map does not claim individual building pairs, verified construction/demolition, or image-confirmed physical change. “2013” and “2023” are edition labels; the online basemap is not historical imagery.

本次未提供含 group_id/partner_ids 的关系索引表，因此不声称逐栋配对，也不把未关联候选说成已核实的新建/拆除或影像确认的物理变化。“2013”“2023”按文件版本标签使用，当前在线底图不是历史影像。