diff -rupN --no-dereference PDAL-2.6.3-src/CMakeLists.txt PDAL-2.6.3-src-new/CMakeLists.txt
--- PDAL-2.6.3-src/CMakeLists.txt	2024-02-06 03:51:45.000000000 +0100
+++ PDAL-2.6.3-src-new/CMakeLists.txt	2024-02-06 11:51:37.838623905 +0100
@@ -117,6 +117,9 @@ include(${PDAL_CMAKE_DIR}/lazperf.cmake)
 include(${PDAL_CMAKE_DIR}/openssl.cmake) # Optional
 include(${PDAL_CMAKE_DIR}/utfcpp.cmake)
 
+find_package(PkgConfig REQUIRED)
+PKG_CHECK_MODULES(EIGEN REQUIRED eigen3)
+
 #------------------------------------------------------------------------------
 # generate the pdal_features.hpp header
 #------------------------------------------------------------------------------
@@ -152,7 +155,6 @@ endif()
 add_subdirectory(plugins)
 
 if (WITH_TESTS)
-    include (${PDAL_CMAKE_DIR}/gtest.cmake)
     add_subdirectory(test)
 endif()
 add_subdirectory(dimbuilder)
@@ -220,7 +222,7 @@ target_include_directories(${PDAL_LIB_NA
         ${ROOT_DIR}
         ${PROJECT_BINARY_DIR}/include
         ${PDAL_VENDOR_DIR}
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
         ${LIBXML2_INCLUDE_DIR}
         ${ZSTD_INCLUDE_DIRS}
         ${NLOHMANN_INCLUDE_DIR}
diff -rupN --no-dereference PDAL-2.6.3-src/plugins/cpd/CMakeLists.txt PDAL-2.6.3-src-new/plugins/cpd/CMakeLists.txt
--- PDAL-2.6.3-src/plugins/cpd/CMakeLists.txt	2024-02-06 03:51:44.000000000 +0100
+++ PDAL-2.6.3-src-new/plugins/cpd/CMakeLists.txt	2024-02-06 11:51:37.842623891 +0100
@@ -11,7 +11,7 @@ find_package(Cpd ${Cpd_VERSION} REQUIRED
 option(BUILD_PLUGIN_CPD "Build Coherent Point Drift support" ${Cpd_FOUND})
 
 set(files filters/CpdFilter.cpp)
-set(include_dirs "${CMAKE_CURRENT_LIST_DIR}" "${PDAL_VENDOR_DIR}/eigen")
+set(include_dirs "${CMAKE_CURRENT_LIST_DIR}" "${EIGEN_INCLUDE_DIRS}")
 
 PDAL_ADD_PLUGIN(filter_libname filter cpd
     FILES
diff -rupN --no-dereference PDAL-2.6.3-src/plugins/rdb/CMakeLists.txt PDAL-2.6.3-src-new/plugins/rdb/CMakeLists.txt
--- PDAL-2.6.3-src/plugins/rdb/CMakeLists.txt	2024-02-06 03:51:44.000000000 +0100
+++ PDAL-2.6.3-src-new/plugins/rdb/CMakeLists.txt	2024-02-06 11:51:37.845623881 +0100
@@ -25,9 +25,8 @@ PDAL_ADD_PLUGIN(libname reader rdb
         ${RDB_INCLUDE_C_DIR}
         ${PDAL_INCLUDE_DIRS}
 )
-target_include_directories(${libname} PRIVATE "${PDAL_VENDOR_DIR}/eigen")
+target_include_directories(${libname} PRIVATE "${EIGEN_INCLUDE_DIRS}")
 target_include_directories(${libname} PUBLIC "${CMAKE_CURRENT_LIST_DIR}/../../vendor/nlohmann/")
-target_include_directories(${libname} PUBLIC "${CMAKE_CURRENT_LIST_DIR}/../../vendor/eigen/")
 
 # windows requires explicit linking against
 # rdbcpp
@@ -54,7 +53,7 @@ if (BUILD_RDBLIB_TESTS)
             ${PROJECT_SOURCE_DIR}/plugins/rdb/io
             ${RDB_INCLUDE_CPP_DIR}
             ${RDB_INCLUDE_C_DIR}
-            ${PDAL_VENDOR_DIR}/eigen
+            ${EIGEN_INCLUDE_DIRS}
 
     )
 endif()
diff -rupN --no-dereference PDAL-2.6.3-src/plugins/teaser/CMakeLists.txt PDAL-2.6.3-src-new/plugins/teaser/CMakeLists.txt
--- PDAL-2.6.3-src/plugins/teaser/CMakeLists.txt	2024-02-06 03:51:44.000000000 +0100
+++ PDAL-2.6.3-src-new/plugins/teaser/CMakeLists.txt	2024-02-06 11:51:37.848623871 +0100
@@ -67,6 +67,6 @@ if (WITH_TESTS)
         LINK_WITH
             ${filter_libname}
         INCLUDES
-            "${PDAL_VENDOR_DIR}/eigen"
+            "${EIGEN_INCLUDE_DIRS}"
     )
 endif()
diff -rupN --no-dereference PDAL-2.6.3-src/plugins/trajectory/CMakeLists.txt PDAL-2.6.3-src-new/plugins/trajectory/CMakeLists.txt
--- PDAL-2.6.3-src/plugins/trajectory/CMakeLists.txt	2024-02-06 03:51:44.000000000 +0100
+++ PDAL-2.6.3-src-new/plugins/trajectory/CMakeLists.txt	2024-02-06 11:51:37.851623860 +0100
@@ -18,7 +18,7 @@ PDAL_ADD_PLUGIN(libname filter trajector
         ${CERES_LIBRARIES}
         ${PDAL_LIBRARIES}
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 
 if (WITH_TRAJECTORY_TEST)
diff -rupN --no-dereference PDAL-2.6.3-src/test/unit/CMakeLists.txt PDAL-2.6.3-src-new/test/unit/CMakeLists.txt
--- PDAL-2.6.3-src/test/unit/CMakeLists.txt	2024-02-06 03:51:44.000000000 +0100
+++ PDAL-2.6.3-src-new/test/unit/CMakeLists.txt	2024-02-06 11:51:37.855623847 +0100
@@ -34,7 +34,7 @@ PDAL_ADD_TEST(pdal_eigen_test
         ${PDAL_SRC_DIR}/private/MathUtils.cpp
 
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 PDAL_ADD_TEST(pdal_file_utils_test FILES FileUtilsTest.cpp)
 PDAL_ADD_TEST(pdal_georeference_test FILES GeoreferenceTest.cpp)
@@ -43,7 +43,7 @@ PDAL_ADD_TEST(pdal_kdindex_test
         KDIndexTest.cpp
     INCLUDES
         ${PDAL_VENDOR_DIR}
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 PDAL_ADD_TEST(pdal_kernel_test FILES KernelTest.cpp)
 PDAL_ADD_TEST(pdal_log_test FILES LogTest.cpp)
@@ -52,7 +52,7 @@ PDAL_ADD_TEST(pdal_math_utils_test
         MathUtilsTest.cpp
         ${PDAL_SRC_DIR}/private/MathUtils.cpp
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 PDAL_ADD_TEST(pdal_metadata_test FILES MetadataTest.cpp)
 PDAL_ADD_TEST(pdal_oldpclblock_test FILES OldPCLBlockTest.cpp)
@@ -84,7 +84,7 @@ PDAL_ADD_TEST(pdal_point_view_test
     FILES
         PointViewTest.cpp
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 PDAL_ADD_TEST(pdal_point_table_test FILES PointTableTest.cpp)
 
@@ -227,13 +227,13 @@ PDAL_ADD_TEST(pdal_io_pcd_reader_test
     FILES
         io/PcdReaderTest.cpp
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 PDAL_ADD_TEST(pdal_io_pcd_writer_test
     FILES
         io/PcdWriterTest.cpp
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 PDAL_ADD_TEST(pdal_io_ply_reader_test
     FILES
@@ -279,7 +279,7 @@ PDAL_ADD_TEST(pdal_i3s_obb_test
     INCLUDES
         ${NLOHMANN_INCLUDE_DIR}
         ${PDAL_INCLUDE_DIR}
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 
 if (BUILD_I3S_TESTS)
@@ -300,7 +300,7 @@ PDAL_ADD_TEST(pdal_filters_chipper_test
         filters/ChipperTest.cpp
     INCLUDES
         ${NLOHMANN_INCLUDE_DIR}
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 PDAL_ADD_TEST(pdal_filters_nndistance_test
     FILES
@@ -359,7 +359,7 @@ PDAL_ADD_TEST(pdal_filters_icp_test
     FILES
         filters/IcpFilterTest.cpp
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen
+        ${EIGEN_INCLUDE_DIRS}
 )
 PDAL_ADD_TEST(pdal_filters_info_test FILES filters/InfoFilterTest.cpp)
 PDAL_ADD_TEST(pdal_filters_lloydkmeans_test FILES filters/LloydKMeansFilterTest.cpp)
@@ -380,7 +380,7 @@ PDAL_ADD_TEST(pdal_filters_planefit_test
     FILES
         filters/PlaneFitFilterTest.cpp
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen)
+        ${EIGEN_INCLUDE_DIRS})
 PDAL_ADD_TEST(pdal_filters_pmf_test FILES filters/PMFFilterTest.cpp)
 PDAL_ADD_TEST(pdal_filters_reprojection_test FILES
     filters/ReprojectionFilterTest.cpp)
@@ -407,7 +407,7 @@ PDAL_ADD_TEST(pdal_filters_splitter_test
     FILES
         filters/SplitterTest.cpp
     INCLUDES
-        ${PDAL_VENDOR_DIR}/eigen)
+        ${EIGEN_INCLUDE_DIRS})
 PDAL_ADD_TEST(pdal_filters_stats_test FILES filters/StatsFilterTest.cpp)
 PDAL_ADD_TEST(pdal_filters_transformation_test FILES
     filters/TransformationFilterTest.cpp)