Calling the GeographicLib C++ library from Excel

You can call GeographicLib functions from Excel. Thanks to Thomas Warner warnerta@gmail.com, for showing me how. This prescription has only been tested for Excel running on a Windows machine. Please let me know if you figure out how to get this working on MacOS versions of Excel.

Here's the overview

Write and compile little interface routines to invoke the functionality you want.
Copy the resulting DLLs to where Excel can find them.
Write an interface script in Visual Basic. This tells Visual Basic about your interfrace routines and it includes definitions of the actual functions you will see exposed in Excel.

Here are the step-by-step instructions for compiling and using the sample routines given here (which solve the direct and inverse geodesic problems and the corresponding rhumb line problems):

Install binary distribution for GeographicLib (either 64-bit or 32-bit to match your version of Excel).
Install a recent version of cmake.
Start a command prompt window and run
```
mkdir BUILD
cd BUILD
cmake -G "Visual Studio 16" -A x64 ..
```
This configures your build. Any of Visual Studio 14, 15, or 16 (corresponding the VS 2015, 2017, 2019) will work. If your Excel is 32-bit, change -A x64 to -A win32. If necessary include -D CMAKE_PREFIX_PATH=DIR to specify where GeographicLib is installed (specified when you ran the GeographicLib installer). Compile the interface with
```
cmake --build . --config Release
```
Copy
```
Release\cgeodesic.dll   # the interface routines
Release\GeographicLib.dll  # the main GeographicLib library
```
to the directory where the Excel executable lives. You can find this directory by launching Excel, launching Task Manager, right-clicking on Excel within Task Manager and selecting Open file location. It's probably something like
```
C:\Program Files\Microsoft Office\root\Office16
```
and you will probably need administrator privileges to do the copy. If it's in Program Files (x86), then you have a 32-bit version of Excel and you need to compile your interface routines in 32-bit by specitying -A win32 when you first run cmake.
Open the Excel workbook within which you would like to use the geodesic and rhumb routines.
Type Alt-F11 to open Excel's Visual Basic editor.
In the left sidebar, right-click on VBAProject (%yourworksheetname%) and select Import File
Browse to Geodesic.bas, select it and click Open
Save your Workbook as Excel Macro-Enabled Workbook (*.xlsm)

You will now have 10 new functions available:

Solve the direct geodesic problem for

lat2: geodesic_direct_lat2(lat1, lon1, azi1, s12)
lon2: geodesic_direct_lon2(lat1, lon1, azi1, s12)
azi2: geodesic_direct_azi2(lat1, lon1, azi1, s12)

Solve the inverse geodesic problem for

s12: geodesic_inverse_s12(lat1, lon1, lat2, lon2)
azi1: geodesic_inverse_azi1(lat1, lon1, lat2, lon2)
azi2: geodesic_inverse_azi2(lat1, lon1, lat2, lon2)

Solve the direct rhumb problem for

lat2: rhumb_direct_lat2(lat1, lon1, azi12, s12)
lon2: rhumb_direct_lon2(lat1, lon1, azi12, s12)

Solve the inverse rhumb problem for

s12: rhumb_inverse_s12(lat1, lon1, lat2, lon2)
azi12: rhumb_inverse_azi12(lat1, lon1, lat2, lon2)

Latitudes, longitudes, and azimuths are in degrees. Distances are in meters.

3.5 KiB Raw Blame History

Calling the GeographicLib C++ library from Excel

3.5 KiB

Raw Blame History