There are two main ways to gain exploration rank:
- Selling cartographic data from exploration
- Completing and receiving payment for sightseeing tour missions
The current wiki chart only focuses on cartographic data. I would suggest using the old one, as below. Think of the numbers as points and not credits.
Aimless 0
Mostly Aimless 20,000
Scout 135,000
Surveyor 570,000
Trailblazer 2,070,000
Pathfinder 5,070,000
Ranger 17,500,000
Pioneer 58,000,000
Elite 156,500,000
The difference being that a lot of things changed with the April '17 release of 2.3 including the "exchange rate" for exploration rank points.
Cartographic (Exploration) is 2 : 1
Passenger (Sightseeing) is 5 : 1
For example, if you took a 10m sightseeing passenger mission as well as getting 20m for exploration scans out and back, you would get 2 + 10 = 12m "points".
Edited to add: Always look at this as from where you are -NOW- going forward. Ignore your credit totals for Exploration on your right hand UI tab, because that only tabulates cartographic payouts.
For example, if you are Pioneer, you need to get 156,500m - 58,000m = 98,500m points to get to Elite if currently at 0% Pioneer. If you are at 50% Pioneer, you would need 98,500m ÷ 2 = 49,250m "points".