Kỹ thuật viên đang khảo sát.

currently

Breakdown of Kỹ thuật viên đang khảo sát.

• kỹ thuật viên: the technician
• khảo sát: to survey; inspect a site

Questions & Answers about Kỹ thuật viên đang khảo sát.

What part of the sentence is the subject, and what part is the verb phrase?

The subject is Kỹ thuật viên, and the verb phrase is đang khảo sát.

• Kỹ thuật viên = technician
• đang khảo sát = is surveying / is inspecting / is conducting a survey

So the basic structure is:

Subject + đang + verb

That is a very common Vietnamese pattern.

Why is đang used here?

đang marks an action as being in progress, similar to English is/are ...-ing.

So:

• khảo sát = survey / inspect / investigate
• đang khảo sát = is surveying / is inspecting

It tells you the action is happening right now or around the current time.

For example:

• Kỹ thuật viên khảo sát. = The technician surveys / surveyed / surveys in general.
  This is more neutral and depends on context.
• Kỹ thuật viên đang khảo sát. = The technician is surveying.
  This clearly shows an ongoing action.

Does Vietnamese always need something like đang for the present progressive?