As per the niruktakara Shri Yaska, Vishnu tattva points towards the Principle of Aditya.
Vishnu Sukta describes the Aditya having expanded in three lokas i.e, Prithvi, Antariksha and Dyu Lokas which denote the 3 subtle planes of consciousness presided by Agni, Vydyutagni and Saura Agni.
They also represent the 3 vyahritis bhuh, bhuvah & suvah.
These 3 planes of Consciousness is described in " vedic symbolism " as the 3 steps of " Vishnu " or " Trivikrama ".
Sakapuni explains this Vishnu Sukta from the " Agni " point of view whereas the Niruktakara explains from " Aditya " perspective.
Whatever may be the principle, it is the Trivikrama tattva that is contemplated here (viseshena kramana kritavan) i.e, conquering and extending Himself into a triple-fold Consciousness with His 3 Strides on Earth, Atmosphere & Heaven.
And such a Trivikrama having expanded Himself in 3 planes with his 3 strides has become all-pervasive i.e, sarva-vyapaka (vish dhatu or vi+upasya with asi dhatu denotes the sarva-vyapti).
Vishnu means " all-pervasive principle ".
Hence, such an Aditya is also called Trivikrama (due to His 3-fold expansion) and also Vishnu (due to His deep penetration in the pindanda & brahmanda & all-pervasiveness).
This stride of three-fold movement of Trivikrama denotes the Journey of Jivatma towards the supreme goal from physical gross.
Now, among the 3 strides of the Trivikrama, the first 2 strides (or the 2 planes of consciousness) can be perceived by Ordinary Mortals.
But the 3rd Stride of 3rd Plane of Consciousness is the TRANSCEDENTAL STATE which is described as " PARAMA PADAM " in this Vishnu Sukta (Ref: tat vishnoh parama padam sadA pashyanti surayah diviva chakshuh atatam).
It is this PARAMA PADAM that has also created 7-lokas or 7-planes of Consciousness with the help of Saptha (7) Chandas. The first rk of the Sukta indicates this with the term " saptha dhAmabhih ".