Complex sentence: In 1615 he surveyed the distance from Alkmaar to Bergen op Zoom, approximately 70 miles (110 kilometres), using a chain of quadrangles containing 33 triangles in all.
Split into simpler sentences: In 1615 he surveyed the distance from Alkmaar to Bergen op Zoom, approximately 70 miles (110 kilometres). The survey was a chain of quadrangles containing 33 triangles in all.