diff --git a/src/app/TileBasemap.cpp b/src/app/TileBasemap.cpp
index a679f9f..7af4d07 100644
--- a/src/app/TileBasemap.cpp
+++ b/src/app/TileBasemap.cpp
@@ -1,5 +1,7 @@
 #include "TileBasemap.hpp"
 
+#include <algorithm>
+#include <cmath>
 #include <cstring>
 
 #include <QImage>
@@ -9,12 +11,17 @@
 #include <QUrl>
 
 #include <vtkActor.h>
+#include <vtkCallbackCommand.h>
+#include <vtkCamera.h>
+#include <vtkCommand.h>
 #include <vtkImageData.h>
+#include <vtkInteractorObserver.h>
 #include <vtkNew.h>
 #include <vtkPlaneSource.h>
 #include <vtkPolyDataMapper.h>
 #include <vtkProperty.h>
 #include <vtkRenderWindow.h>
+#include <vtkRenderWindowInteractor.h>
 #include <vtkRenderer.h>
 #include <vtkTexture.h>
 
@@ -27,68 +34,176 @@ namespace geopro::app {
 namespace {
 // 天地图 WMTS 令牌（与轨迹图 trajectory_map.html 同源）。
 const char* kTk = "aca91d8c9f59a4f779f39061b8a07737";
-constexpr int kZoom = 16;       // 固定层级(MVP)：单瓦片 ~数百米，半径覆盖典型测线
-constexpr int kRadius = 3;      // 中心瓦片 ±3 → 7x7=49 块，约数公里
-constexpr double kGroundZ = 0.0;  // 底图置于 z=0 地面参考（剖面深度向下为负，落其下）
+constexpr int kRadius = 3;            // 中心瓦片 ±3 → 最多 7x7=49 块，留平移余量
+constexpr int kMinZoom = 3;
+constexpr int kMaxZoom = 18;
+constexpr double kGroundZ = 0.0;      // 底图置于 z=0 地面参考（剖面深度向下为负，落其下）
+constexpr double kPi = 3.14159265358979323846;
+constexpr double kEarthCirc = 40075016.686;  // 赤道周长(米) = z0 单瓦片地面尺寸
+constexpr double kTilesAcross = 4.0;          // 视野跨度目标覆盖瓦片数（决定层级）
+
+// key 打包：z<<44 | x<<22 | y（z≤18, x/y<2^18 < 2^22）。
+void unpackKey(long long key, int& z, int& x, int& y) {
+    z = static_cast<int>(key >> 44);
+    x = static_cast<int>((key >> 22) & 0x3FFFFF);
+    y = static_cast<int>(key & 0x3FFFFF);
+}
 }  // namespace
 
+long long TileBasemap::tileKey(int z, int x, int y) {
+    return (static_cast<long long>(z) << 44) | (static_cast<long long>(x) << 22) |
+           static_cast<long long>(y);
+}
+
 TileBasemap::TileBasemap(geopro::render::Scene& scene, vtkRenderWindow* rw,
                          std::shared_ptr<geopro::core::GeoLocalFrame> frame, QObject* parent)
     : QObject(parent), scene_(scene), rw_(rw), frame_(std::move(frame)) {}
 
-void TileBasemap::clearTiles() {
-    for (auto& a : tiles_) scene_.renderer()->RemoveViewProp(a);
-    tiles_.clear();
+TileBasemap::~TileBasemap() {
+    if (styleObs_ && observer_) styleObs_->RemoveObserver(observer_);
 }
 
-void TileBasemap::hide() {
-    ++generation_;
-    clearTiles();
-    if (rw_) rw_->Render();
+void TileBasemap::ensureObserver() {
+    if (styleObs_) return;
+    if (!rw_) return;
+    auto* iren = rw_->GetInteractor();
+    if (!iren) return;
+    auto* style = iren->GetInteractorStyle();  // EndInteractionEvent 由交互样式发出
+    if (!style) return;
+    styleObs_ = style;
+    observer_ = vtkSmartPointer<vtkCallbackCommand>::New();
+    observer_->SetClientData(this);
+    observer_->SetCallback(&TileBasemap::onInteractionEnd);
+    styleObs_->AddObserver(vtkCommand::EndInteractionEvent, observer_);
 }
 
+void TileBasemap::onInteractionEnd(vtkObject*, unsigned long, void* clientData, void*) {
+    if (auto* self = static_cast<TileBasemap*>(clientData)) self->refresh();
+}
+
+void TileBasemap::hide() { show(Hidden); }
+
 void TileBasemap::show(Kind kind) {
-    clearTiles();
+    ensureObserver();
+    ++generation_;  // 旧回包(含换源前的层)按 generation 丢弃
+    for (auto& kv : placed_) scene_.renderer()->RemoveViewProp(kv.second);
+    placed_.clear();
+    inFlight_.clear();
+    desired_.clear();
+    kind_ = kind;
     if (kind == Hidden) {
-        ++generation_;
         if (rw_) rw_->Render();
         return;
     }
-    const int myGen = ++generation_;
-    const auto c = frame_->toLatLon(0.0, 0.0);  // 数据原点经纬（已重锚到真实剖面中心）
-    const geopro::render::TileXY center = geopro::render::lonLatToTile(c.lon, c.lat, kZoom);
-    const QString layerDir = (kind == Satellite) ? QStringLiteral("img_w") : QStringLiteral("vec_w");
-    const QString layer = (kind == Satellite) ? QStringLiteral("img") : QStringLiteral("vec");
-    const int n = 1 << kZoom;
+    refresh();
+}
+
+bool TileBasemap::computeView(double& centerLat, double& centerLon, int& zoom) const {
+    auto* ren = scene_.renderer();
+    if (!ren) return false;
+    auto* cam = ren->GetActiveCamera();
+    if (!cam) return false;
+
+    double fp[3];
+    cam->GetFocalPoint(fp);
+    const auto c = frame_->toLatLon(fp[0], fp[1]);  // 焦点局部米(x East,y North) → 经纬
+    centerLat = c.lat;
+    centerLon = c.lon;
+
+    // 视野在地面的近似跨度(米)：透视用 2·dist·tan(半 FOV)，平行投影用 2·parallelScale。
+    double span;
+    if (cam->GetParallelProjection()) {
+        span = 2.0 * cam->GetParallelScale();
+    } else {
+        const double halfAngle = cam->GetViewAngle() * 0.5 * kPi / 180.0;
+        span = 2.0 * cam->GetDistance() * std::tan(halfAngle);
+    }
+    span = std::clamp(span, 1.0, 4.0e7);
+
+    const double cosLat = std::max(0.01, std::cos(centerLat * kPi / 180.0));
+    const double tileMeters = span / kTilesAcross;
+    int z = static_cast<int>(std::lround(std::log2(kEarthCirc * cosLat / tileMeters)));
+    zoom = std::clamp(z, kMinZoom, kMaxZoom);
+    return true;
+}
+
+void TileBasemap::refresh() {
+    if (kind_ == Hidden || refreshing_) return;
+    refreshing_ = true;
+
+    double clat = 0, clon = 0;
+    int zoom = 0;
+    if (!computeView(clat, clon, zoom)) {
+        refreshing_ = false;
+        return;
+    }
+
+    const geopro::render::TileXY center = geopro::render::lonLatToTile(clon, clat, zoom);
+    const int n = 1 << zoom;
+    desired_.clear();
     for (int dy = -kRadius; dy <= kRadius; ++dy) {
         for (int dx = -kRadius; dx <= kRadius; ++dx) {
             const int tx = center.x + dx, ty = center.y + dy;
             if (tx < 0 || ty < 0 || tx >= n || ty >= n) continue;
-            const int sub = (tx + ty) % 8;  // 子域负载分担 t0-t7
-            const QString url =
-                QStringLiteral("http://t%1.tianditu.gov.cn/%2/wmts?service=wmts&request=GetTile"
-                               "&version=1.0.0&LAYER=%3&tileMatrixSet=w&TileMatrix=%4&TileRow=%5"
-                               "&TileCol=%6&style=default&format=tiles&tk=%7")
-                    .arg(sub)
-                    .arg(layerDir, layer)
-                    .arg(kZoom)
-                    .arg(ty)
-                    .arg(tx)
-                    .arg(QString::fromLatin1(kTk));
-            QNetworkReply* reply = nam_.get(QNetworkRequest(QUrl(url)));
-            connect(reply, &QNetworkReply::finished, this, [this, reply, tx, ty, myGen]() {
-                reply->deleteLater();
-                if (myGen != generation_) return;  // 已被新的 show/hide 取代 → 丢弃
-                if (reply->error() != QNetworkReply::NoError) return;
-                QImage img;
-                if (!img.loadFromData(reply->readAll())) return;
-                placeTile(kZoom, tx, ty, img);
-            });
+            desired_.insert(tileKey(zoom, tx, ty));
         }
     }
+
+    // 移除离开视野/换层级的瓦片。
+    for (auto it = placed_.begin(); it != placed_.end();) {
+        if (desired_.find(it->first) == desired_.end()) {
+            scene_.renderer()->RemoveViewProp(it->second);
+            it = placed_.erase(it);
+        } else {
+            ++it;
+        }
+    }
+
+    // 拉取缺失瓦片。
+    for (long long key : desired_) {
+        if (placed_.count(key) || inFlight_.count(key)) continue;
+        int z, x, y;
+        unpackKey(key, z, x, y);
+        fetchTile(z, x, y, key);
+    }
+
+    if (rw_) rw_->Render();
+    refreshing_ = false;
 }
 
-void TileBasemap::placeTile(int z, int x, int y, const QImage& img) {
+void TileBasemap::fetchTile(int z, int x, int y, long long key) {
+    const QString layerDir = (kind_ == Satellite) ? QStringLiteral("img_w") : QStringLiteral("vec_w");
+    const QString layer = (kind_ == Satellite) ? QStringLiteral("img") : QStringLiteral("vec");
+    const int sub = (x + y) % 8;  // 子域负载分担 t0-t7
+    const QString url =
+        QStringLiteral("http://t%1.tianditu.gov.cn/%2/wmts?service=wmts&request=GetTile"
+                       "&version=1.0.0&LAYER=%3&tileMatrixSet=w&TileMatrix=%4&TileRow=%5"
+                       "&TileCol=%6&style=default&format=tiles&tk=%7")
+            .arg(sub)
+            .arg(layerDir, layer)
+            .arg(z)
+            .arg(y)
+            .arg(x)
+            .arg(QString::fromLatin1(kTk));
+
+    const int gen = generation_;
+    inFlight_.insert(key);
+    QNetworkReply* reply = nam_.get(QNetworkRequest(QUrl(url)));
+    connect(reply, &QNetworkReply::finished, this, [this, reply, key, z, x, y, gen]() {
+        reply->deleteLater();
+        inFlight_.erase(key);
+        if (gen != generation_) return;                     // 换源/隐藏后丢弃
+        if (kind_ == Hidden) return;
+        if (desired_.find(key) == desired_.end()) return;   // 已移出视野
+        if (placed_.count(key)) return;
+        if (reply->error() != QNetworkReply::NoError) return;
+        QImage img;
+        if (!img.loadFromData(reply->readAll())) return;
+        placeTile(key, z, x, y, img);
+    });
+}
+
+void TileBasemap::placeTile(long long key, int z, int x, int y, const QImage& img) {
     const geopro::render::LonLatBox b = geopro::render::tileBounds(z, x, y);
     const auto sw = frame_->toLocal(b.south, b.west);
     const auto se = frame_->toLocal(b.south, b.east);
@@ -125,7 +240,7 @@ void TileBasemap::placeTile(int z, int x, int y, const QImage& img) {
     actor->GetProperty()->LightingOff();  // 底图不受场景光照
 
     scene_.addActor(actor);
-    tiles_.push_back(actor);
+    placed_[key] = actor;
     if (rw_) rw_->Render();
 }
 
diff --git a/src/app/TileBasemap.hpp b/src/app/TileBasemap.hpp
index ab5bdd0..b0cdf83 100644
--- a/src/app/TileBasemap.hpp
+++ b/src/app/TileBasemap.hpp
@@ -3,42 +3,57 @@
 #include <QNetworkAccessManager>
 #include <QObject>
 
+#include <map>
 #include <memory>
-#include <vector>
+#include <set>
 
 #include <vtkSmartPointer.h>
 
 class vtkActor;
+class vtkObject;
 class vtkRenderWindow;
+class vtkInteractorObserver;
+class vtkCallbackCommand;
 class QImage;
 namespace geopro::render { class Scene; }
 namespace geopro::core { class GeoLocalFrame; }
 
 namespace geopro::app {
 
-// 天地图 WMTS 底图层：以共享 GeoLocalFrame 原点为中心，异步拉取覆盖瓦片贴成地面纹理面(z=0)。
-// 复用轨迹图同款 token/WMTS。瓦片经同一 frame 配准 → 自动与帘面/轨迹对齐。
-// 注：本期固定 zoom + 固定覆盖半径(MVP)，相机驱动 LOD/数据范围自适应后续再加。
+// 天地图 WMTS 底图层（局部平面，B 方案）+ LOD：按相机视距自动选瓦片层级、覆盖可视范围，
+// 缩放/平移结束后增量增删瓦片。复用轨迹图同款 token；瓦片经同一 GeoLocalFrame 配准。
 class TileBasemap : public QObject {
     Q_OBJECT
 public:
     enum Kind { Street = 0, Satellite = 1, Hidden = 2 };
     TileBasemap(geopro::render::Scene& scene, vtkRenderWindow* rw,
                 std::shared_ptr<geopro::core::GeoLocalFrame> frame, QObject* parent = nullptr);
+    ~TileBasemap() override;
 
-    void show(Kind kind);  // 拉取并显示（Hidden 等同 hide）
-    void hide();           // 移除全部瓦片面
+    void show(Kind kind);  // 显示某底图（Hidden 等同 hide）；记住类型供 LOD 刷新复用
+    void hide();           // 移除全部瓦片
+    void refresh();        // 按当前相机重算层级+覆盖，增量更新瓦片（交互结束回调）
 
 private:
-    void clearTiles();
-    void placeTile(int z, int x, int y, const QImage& img);
+    static long long tileKey(int z, int x, int y);
+    void ensureObserver();  // 首次显示时挂到交互样式的 EndInteractionEvent
+    bool computeView(double& centerLat, double& centerLon, int& zoom) const;
+    void fetchTile(int z, int x, int y, long long key);
+    void placeTile(long long key, int z, int x, int y, const QImage& img);
+    static void onInteractionEnd(vtkObject*, unsigned long, void* clientData, void*);
 
     geopro::render::Scene& scene_;
     vtkRenderWindow* rw_;
     std::shared_ptr<geopro::core::GeoLocalFrame> frame_;
     QNetworkAccessManager nam_;
-    std::vector<vtkSmartPointer<vtkActor>> tiles_;
-    int generation_ = 0;  // 每次 show/hide 自增；迟到的瓦片回包比对丢弃
+    Kind kind_ = Hidden;
+    int generation_ = 0;                                    // show/hide/换源 自增，丢弃过期回包
+    std::map<long long, vtkSmartPointer<vtkActor>> placed_;  // 已贴瓦片：key→actor
+    std::set<long long> desired_;                           // 当前视野应显示的瓦片 key
+    std::set<long long> inFlight_;                          // 在途请求，避免重复拉
+    vtkSmartPointer<vtkInteractorObserver> styleObs_;       // 持引用保证回调期有效
+    vtkSmartPointer<vtkCallbackCommand> observer_;
+    bool refreshing_ = false;
 };
 
 }  // namespace geopro::app