Depends on your audience. If your audience consists mostly of programmers, use top-left they are familiar with. If your audience is familiar with primary scho

Depends on your audience. If your audience consists mostly of programmers, use top-left they are familiar with. If your audience is familiar with primary school math, choose their coordinate system: bottom-left. It is just convention that is consistently kept within the certain community. I would advise against any convention that is unused in your community.