Learn Hardcore Russian: Наложение границ обнаружили на схеме расположения. - The boundary overlap was discovered on the location diagram.

This is a very common Russian pattern: past tense plural with no stated subject can mean someone/they found it, where the exact people are not important.

So обнаружили literally means they discovered/found, but in English we often translate this more naturally as a passive:

They discovered an overlap of boundaries...
An overlap of boundaries was discovered...

This is called an indefinite-personal use. It is especially common in reports, official writing, and technical language.

What case is наложение here?

Here наложение is the direct object of обнаружили, so syntactically it is in the accusative case.

However, because наложение is:

neuter
singular
inanimate

its accusative form is the same as its nominative form.

So the form stays наложение.

Dictionary form: наложение

Why is границ in the genitive plural?