diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index a0d2a72..f1fb57d 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -1,13 +1,15 @@
 find_package(Eigen3 CONFIG REQUIRED)
+find_package(PROJ CONFIG REQUIRED)
 
 add_library(geopro_core STATIC
   geo/LocalFrame.cpp
+  geo/CrsTransform.cpp
   model/ColorScale.cpp
   algo/IdwInterpolator.cpp
 )
 
 target_include_directories(geopro_core PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
-target_link_libraries(geopro_core PUBLIC Eigen3::Eigen)
+target_link_libraries(geopro_core PUBLIC Eigen3::Eigen PROJ::proj)
 target_compile_features(geopro_core PUBLIC cxx_std_17)
 
 # 铁律：core 为纯业务逻辑层，绝不链接 Qt / VTK。
diff --git a/src/core/geo/CrsTransform.cpp b/src/core/geo/CrsTransform.cpp
new file mode 100644
index 0000000..c49f734
--- /dev/null
+++ b/src/core/geo/CrsTransform.cpp
@@ -0,0 +1,37 @@
+#include "geo/CrsTransform.hpp"
+#include <proj.h>
+#include <stdexcept>
+namespace geopro::core {
+
+struct CrsTransform::Impl {
+    PJ_CONTEXT* ctx = nullptr;
+    PJ* pj = nullptr;
+};
+
+CrsTransform::CrsTransform(const std::string& src, const std::string& dst)
+    : impl_(std::make_unique<Impl>()) {
+    impl_->ctx = proj_context_create();
+    impl_->pj = proj_create_crs_to_crs(impl_->ctx, src.c_str(), dst.c_str(), nullptr);
+    if (!impl_->pj) throw std::runtime_error("CrsTransform: failed to create " + src + "->" + dst);
+    PJ* norm = proj_normalize_for_visualization(impl_->ctx, impl_->pj);
+    if (norm) { proj_destroy(impl_->pj); impl_->pj = norm; }
+}
+
+CrsTransform::~CrsTransform() {
+    if (impl_->pj) proj_destroy(impl_->pj);
+    if (impl_->ctx) proj_context_destroy(impl_->ctx);
+}
+
+Xy CrsTransform::forward(double x, double y) const {
+    PJ_COORD c = proj_coord(x, y, 0, 0);
+    PJ_COORD r = proj_trans(impl_->pj, PJ_FWD, c);
+    return Xy{r.xy.x, r.xy.y};
+}
+
+Xy CrsTransform::inverse(double x, double y) const {
+    PJ_COORD c = proj_coord(x, y, 0, 0);
+    PJ_COORD r = proj_trans(impl_->pj, PJ_INV, c);
+    return Xy{r.xy.x, r.xy.y};
+}
+
+}  // namespace geopro::core
diff --git a/src/core/geo/CrsTransform.hpp b/src/core/geo/CrsTransform.hpp
new file mode 100644
index 0000000..6ac7409
--- /dev/null
+++ b/src/core/geo/CrsTransform.hpp
@@ -0,0 +1,20 @@
+#pragma once
+#include <string>
+#include <memory>
+namespace geopro::core {
+
+struct Xy { double x, y; };
+
+// PROJ 封装：源 CRS <-> 目标 CRS。用于世界系<->GIS<->经纬度、影像异源 CRS 重投影(设计 §5)。
+class CrsTransform {
+public:
+    CrsTransform(const std::string& srcCrs, const std::string& dstCrs);
+    ~CrsTransform();
+    Xy forward(double x, double y) const;   // src -> dst
+    Xy inverse(double x, double y) const;   // dst -> src
+private:
+    struct Impl;
+    std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace geopro::core
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 4d7024a..d296baf 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -7,12 +7,25 @@ add_executable(geopro_tests smoke_test.cpp)
 target_link_libraries(geopro_tests PRIVATE GTest::gtest GTest::gtest_main)
 
 include(GoogleTest)
-gtest_discover_tests(geopro_tests)
+
+# PROJ 运行时需要数据目录（proj.db 等）。vcpkg 把数据装在 share/proj 下。
+# 通过测试环境变量 PROJ_DATA 注入，使 `ctest -R CrsTransform` 无需调用方手动 set。
+file(GLOB _proj_data_dirs
+  "${CMAKE_BINARY_DIR}/vcpkg_installed/*/share/proj"
+)
+if(_proj_data_dirs)
+  list(GET _proj_data_dirs 0 GEOPRO_PROJ_DATA)
+  gtest_discover_tests(geopro_tests
+    PROPERTIES ENVIRONMENT "PROJ_DATA=${GEOPRO_PROJ_DATA}")
+else()
+  gtest_discover_tests(geopro_tests)
+endif()
 
 target_sources(geopro_tests PRIVATE core/test_local_frame.cpp)
 target_sources(geopro_tests PRIVATE core/test_model.cpp)
 target_sources(geopro_tests PRIVATE core/test_color_scale.cpp)
 target_sources(geopro_tests PRIVATE core/test_idw.cpp)
+target_sources(geopro_tests PRIVATE core/test_crs_transform.cpp)
 target_link_libraries(geopro_tests PRIVATE geopro_core)
 
 add_subdirectory(spike)   # spike S3: banded contour 渲染验证
diff --git a/tests/core/test_crs_transform.cpp b/tests/core/test_crs_transform.cpp
new file mode 100644
index 0000000..1c83454
--- /dev/null
+++ b/tests/core/test_crs_transform.cpp
@@ -0,0 +1,26 @@
+#include <gtest/gtest.h>
+#include "geo/CrsTransform.hpp"
+using namespace geopro::core;
+
+// UTM 49N (CM 111°E, false easting 500000) <-> WGS84 经纬度往返。
+// 输入 easting≈516868 仅比中央经线偏东 ~16.9km，故经度落在 ~111.16°E（非 114°）。
+// normalize_for_visualization 后：forward 输出 (lon, lat)，inverse 输入 (lon, lat)。
+TEST(CrsTransform, Utm49nToWgs84RoundTrip) {
+    CrsTransform t("EPSG:32649", "EPSG:4326");
+    auto ll = t.forward(516868.0, 2494259.0);   // (east,north) -> (lon,lat)
+    EXPECT_NEAR(ll.x, 111.16, 0.05);            // lon
+    EXPECT_NEAR(ll.y, 22.55, 0.05);             // lat
+    auto en = t.inverse(ll.x, ll.y);            // (lon,lat) -> (east,north)
+    EXPECT_NEAR(en.x, 516868.0, 1.0);
+    EXPECT_NEAR(en.y, 2494259.0, 1.0);
+}
+
+// WebMercator -> UTM 49N 异源重投影（设计 §5 影像重投影）。
+// tfw 原点经度真实约 114.16°E，距 49N 中央经线 111°E 偏东 ~3.16°，
+// 故其 49N easting 远大于 false easting，落在 ~825km 处（合理且 < UTM 带宽上限）。
+TEST(CrsTransform, WebMercatorToUtm) {
+    CrsTransform t("EPSG:3857", "EPSG:32649");
+    auto p = t.forward(12708343.88, 2577685.90);  // tfw 原点
+    EXPECT_GT(p.x, 800000.0); EXPECT_LT(p.x, 850000.0);   // UTM 49N 合理 Easting
+    EXPECT_GT(p.y, 2400000.0); EXPECT_LT(p.y, 2600000.0); // 合理 Northing
+}
diff --git a/vcpkg.json b/vcpkg.json
index 22cff44..77981b0 100644
--- a/vcpkg.json
+++ b/vcpkg.json
@@ -5,6 +5,7 @@
   "dependencies": [
     "eigen3",
     "gtest",
-    "nlohmann-json"
+    "nlohmann-json",
+    "proj"
   ]
 }