When are customer journey maps useful?

How do I find data to build customer journey maps?

I ran some surveys but I don't think that survey answers are useful enough to build a customer journey map. I don't have enough emotional data, but I don't know how to get them.

Maybe through interviews? And in this case, the interview have to be made before the dev of the website or service, or after that this is already developed?

I'm asking this question because, before start working on my project I ran some survey to get insights from users, to shape the experience. But I noticed that data I got aren't enough useful to know their emotion during the use of the site.

Lastly: at what stage in a project would it be the right time to develop a customer journey map?