How to make your own borehole siting equipment?
Professional (Vertical Electric Sounding) VES machines cost at least € 3000. You can make one for just € 300. It works a bit less comfortable but it provides the same accuracy because they use the same technique. Learn here how https://jacana.help/news/making-borehole-siting-machines/
There is also a manual that explains how to use it at https://jacana.help/resources/water