Catamaran- from the Tamil kattumaram; kattu, tie + maram, log, tree.

Arab astronomers made exquisite astrolabes, so I would think sailors would find access. I recall a "National Geographic" artcile showing a string of specific length to which was attached a disc that looked much like a coin. The string was held in the mouth and the horizon was sited through a hole in the disc. I don't recall what calculations were made.

If I can ever find my copy of "Canoes of Oceania" I'll look for more specific reference to Indo-Polynesian cultural link. I'm sure it exists.

In any case, if "they took elevations with their hands. . ." and "they regularly sailed from Southern Iraq to Guangzhou in China. . ." then they are skilled enough to meet my personal test.