Ubuntu 20.04 build issue ( Could NOT find Proj (missing: PROJ_INCLUDE_DIRS))

[a180285]

Hi I'm using ubuntu 20.04 to build vts-tools,

When I type make -j8, I got following errors.

* Building in build
-- Configuring build system on Linux machine
-- Using /usr/bin/python3 as buildsys python.
-- Release mode: Compiling with debug symbols by default. To disable set the BUILDSYS_RELEASE_NDEBUG variable.
-- using /home/unity/vts-tools/tools/buildsys/cmake/tools/file2cpp/file2cpp as file2cpp
-- using /home/unity/vts-tools/tools/buildsys/cmake/tools/sqlite32cpp/sqlite32db as sqlite32db
-- using /home/unity/vts-tools/tools/buildsys/cmake/tools/py2cpp/py2pyc as py2pyc
-- using /home/unity/vts-tools/tools/buildsys/cmake/tools/pathstrip/pathstrip as pathstrip
-- using /home/unity/vts-tools/tools/buildsys/cmake/tools/py-runnable/py-runnable as py-runnable
-- using /home/unity/vts-tools/tools/buildsys/cmake/tools/compile-pyc/compile-pyc as compile-pyc
-- Setting up project <vts-tools>, version <test>.
-- Build type: <Release>.
-- Enabled C++14 for C++ (GNU)
-- Enabled C11 for C (GNU)
-- Found OpenMP_C: -fopenmp
-- Found OpenMP_CXX: -fopenmp
-- Found OpenMP: TRUE
-- Found OpenMP.
CMake Error at /usr/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:146 (message):
  Could NOT find Proj (missing: PROJ_INCLUDE_DIRS)
Call Stack (most recent call first):
  /usr/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:393 (_FPHSA_FAILURE_MESSAGE)
  buildsys/cmake/Modules/FindProj.cmake:29 (find_package_handle_standard_args)
  CMakeLists.txt:29 (find_package)


-- Configuring incomplete, errors occurred!
See also "/home/unity/vts-tools/tools/build/CMakeFiles/CMakeOutput.log".
See also "/home/unity/vts-tools/tools/build/CMakeFiles/CMakeError.log".
make: *** [Makefile:23: all] Error 1