It always pays to be cautious rather than being too optimistic, so the cautionary note from you is welcome.
Let me clarify the statement below based on my understanding:
I have understood that management has cautiously - and so prudently- decided not to go for anything new till this ~40k line kilometres 2d survey gets over.
The above statement is not correct. The project will be completed only by Sept '19. Management has decided not to bid till this project stabilizes not till the completion of the project. There is a big difference in your statement and management guidance. Management will most likely start bidding towards the second half of FY18(my understanding from interaction with management from AGM last year).
Alphageo is in a business where order book is important. 3 year order visibility is rare for this kind of business. They may not get such large orders within India in future and sales might dip post completion of this order. But such large orders give time to management to think about expanding their offerings. During the AGM they hinted about their foray into shallow water survey. Also with the demonstration of such large execution ability then will be able to bid globally as well.
Due to nature of this business, alphageo will always get a lower discounting compared to compounding stories. However, with full execution there is a strong possibility of large upside from here(although no multibagger opportunity). I will review my position after a year and take a call.
Disc: Invested and fully biased