I was thinking that he had been summoned as a result of failure to pay a debt (not unusual, I think, in those ... everyone seemed to be demanding repayment of loans etc) ... but 'Late teens' ? I'm not sure of his age when surveying , but surely it was in his 20s.
Anyway, I'll say it was a debt for surveying equipment/tools and someone came in and paid it for him (this is when I need to access a book).
“The honest man, tho' e'er sae poor,
Is king o' men for a' that” Robert Burns