BPHS ch. 11 separates journeys from residence. This surface reads the houses the chapter actually names.
BPHS ch. 11 uses two different words and puts them in two different houses. Journeys belong to the third (v. 4) and travel to the seventh (v. 8), but living in foreign lands is named in the tenth (v. 11), in the same verse as livelihood, profession, authority, honour and the father. That is the distinction this page is built on, and it is why a settlement reading here is not a travel reading with a longer horizon.
It also explains, with no extra doctrine required, why work abroad is the best attested of the three cases the page separates: BPHS 11.11 carries profession and foreign residence in one verse, so the combination needs no second rule to justify it. Study abroad and permanent migration each need a second house, and the page names which one and why rather than folding them all into a single verdict.
Study abroad is read as the fifth and the tenth held side by side: the fifth because BPHS 11.6 gives it learning and knowledge, and the tenth because 11.11 gives it living in foreign lands. Two verses, both named. Work abroad is read from the tenth alone, on one verse, and is the strongest of the three for that reason.
Permanent migration is read as the tenth against the fourth, because 11.5 gives the fourth conveyances, kinsfolk, the mother, domestic ease, land and dwellings, which is what a migration displaces, with the twelfth beside it for expenditure (11.13).
Each case is rendered as its constituent houses with their own three legs under Phaladeepika ch. 15. They are never scored against each other and no case is declared the likely one. A comparison of two independently cited readings is a fact about a chart; a ranking of the three would be a weighting no text supplies, and this app excludes composites the sources do not weight.
The first is that Rahu in the first, seventh, ninth or twelfth house makes a native likely to live or work abroad. It has no locus in the corpus this app has read. Phaladeepika 15.15-16 gives Rahu exactly one karakatva, the paternal grandfather, and gives it nothing else; the brevity of that entry is a verified feature of the text, not an abridgement made here. No verse read for this feature associates Rahu with foreign lands.
The second is that the sign of the twelfth lord gives the direction of foreign settlement. The direction column on a rasi is one of the attributes this repo's own per-attribute provenance table does not cite, and no verse read here routes settlement by it.
Both rules are reported on the surface at the app-convention tier, next to the verse-attested reading, so that a reader can see exactly which claim has a chapter behind it and which has only circulation. Naming them is more useful than silently repeating them and more honest than pretending they are not what most readers have been told.
A departure is an event, and this app times events the way the chapter does. Phaladeepika 16.32 reads Jupiter transiting a trine to the rasi or the navamsa of the relevant bhava's lord as the realisation of that bhava's good, and the page computes it for the fifth, the tenth and the twelfth so that a study window and a work window are distinguishable rather than collapsed into one.
Phaladeepika 17.1 supplies the adverse limb, Saturn on the lord of the eighth or twelfth counted from that bhava.
Alongside those, Phaladeepika ch. XX contributes the dashas of the third, ninth, tenth and twelfth lords, each carrying both halves of the chapter with its own six-clause strength test selecting between them and reporting undetermined where it does not decide. A visa is not in any of these texts and this page does not pretend otherwise. What is offered is the classical window for the bhava whose matter a departure belongs to, which is a different and more checkable thing than a date.
The page needs a date of birth, a time of birth and a birth place, from which it takes coordinates and time zone. The chart is cast on the Lahiri ayanamsha with whole-sign houses and positions computed to sub-arcsecond precision.
Because whole-sign houses make the tenth simply the tenth sign from the lagna, the reading is stable across small errors in the recorded minute, though the transit and dasha windows are not: a dasha boundary lands on a specific date, and a shifted birth time shifts the whole tree.
It will not name a country, a city or a direction, because the rule that would supply one is the untraced twelfth-lord rule described above. It will not tell you whether a particular application will succeed, because no verse read for this feature speaks to that.
And it will not rank study, work and migration against each other. What it gives is which houses the chapter assigns to each case, how those houses stand in your chart, and when the chapter's own transit and dasha rules mark their windows.