Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 8 · Marriage
विवाहः
गोचरं वेधजं चाष्टवर्गजं रूपजं बलम् ।यथोत्तरं बलाधिक्यं स्थूलं गोचरमार्गजम् ॥ ४२८ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 428.
Strength comes from gochara (transit through a sign) and from vedha (blocking point). It also comes from the ashtakavarga (eight-source point table) and from rupa (unit of strength). Each later one is stronger. The one from the transit path is the rough one.
Simple meaning: Transit strength is the roughest. Blocking, ashtakavarga and counted strength are each finer.
चंद्रताराबलं वीक्ष्य ततः पंचांगजं बलम् ।
Check the Moon and star strength, then the almanac parts, which count one, two and three.
योगश्चतुर्गुणः पञ्चगुणं तिथ्यर्द्धसंज्ञितम् ।
Each part counts more in turn: yoga four, karana five, then the hour and the lagna.
ततो बलवती होरा द्रेष्काणो बलवांस्ततः ।
The finer parts of the sign grow stronger in turn: hora, drekkana, navamsha, then dvadashamsha.