diff --git a/src/app/VtkSceneView.cpp b/src/app/VtkSceneView.cpp
index a10db8a..3988d7b 100644
--- a/src/app/VtkSceneView.cpp
+++ b/src/app/VtkSceneView.cpp
@@ -88,7 +88,8 @@ void VtkSceneView::addCurtain(const geopro::core::Grid& grid, const geopro::core
             la0 = std::min(la0, grid.lat[i]); la1 = std::max(la1, grid.lat[i]);
             lo0 = std::min(lo0, grid.lon[i]); lo1 = std::max(lo1, grid.lon[i]);
         }
-        frame_ = std::make_shared<geopro::core::GeoLocalFrame>((la0 + la1) / 2.0, (lo0 + lo1) / 2.0);
+        // 就地重锚共享 frame（不换对象）→ 同持此 frame 的底图层等随即一致对齐。
+        frame_->reanchor((la0 + la1) / 2.0, (lo0 + lo1) / 2.0);
         frameAnchoredToData_ = true;
     }
     auto curtain = geopro::render::buildCurtain(grid, cs, *frame_);
diff --git a/src/core/geo/GeoLocalFrame.cpp b/src/core/geo/GeoLocalFrame.cpp
index 0b77b38..62273f1 100644
--- a/src/core/geo/GeoLocalFrame.cpp
+++ b/src/core/geo/GeoLocalFrame.cpp
@@ -17,6 +17,13 @@ GeoLocalFrame::GeoLocalFrame(double lat0, double lon0)
       mPerDegLon_(kMetersPerDegLonEquator * std::cos(lat0 * kPi / 180.0)),
       mPerDegLat_(kMetersPerDegLat) {}
 
+void GeoLocalFrame::reanchor(double lat0, double lon0) {
+    lat0_ = lat0;
+    lon0_ = lon0;
+    mPerDegLon_ = kMetersPerDegLonEquator * std::cos(lat0 * kPi / 180.0);
+    // mPerDegLat_ 为常数，无需更新。
+}
+
 LocalXY GeoLocalFrame::toLocal(double lat, double lon) const {
     return LocalXY{(lon - lon0_) * mPerDegLon_, (lat - lat0_) * mPerDegLat_};
 }
diff --git a/src/core/geo/GeoLocalFrame.hpp b/src/core/geo/GeoLocalFrame.hpp
index ceec27b..7a97ce2 100644
--- a/src/core/geo/GeoLocalFrame.hpp
+++ b/src/core/geo/GeoLocalFrame.hpp
@@ -9,6 +9,8 @@ struct LatLon { double lat, lon; };
 class GeoLocalFrame {
 public:
     GeoLocalFrame(double lat0, double lon0);
+    // 就地改原点（不换对象）：所有持有此共享 frame 的渲染层(帘面/底图/坐标轴)随即一致重定位。
+    void reanchor(double lat0, double lon0);
     LocalXY toLocal(double lat, double lon) const;  // -> (x East m, y North m)
     // toLocal 的反算：局部米 (x East, y North) -> 经纬度。
     // lon = lon0 + x/mPerDegLon，lat = lat0 + y/mPerDegLat（坐标轴经纬度刻度用）。