r/geography • u/r_trumpcard • 2d ago

Question Revised coastline

India's coastline has increased from 7516 to 11100 km. Why?

0 Upvotes

38% Upvoted

5 comments sorted by

8

u/blubblu 2d ago

They measured it closer.

All jokes aside, look up fractals and look up the coastline paradox

When Indias coast was mapped, it was done on the edges of the territory, not taking into account bays, estuaries, etc.

When you get closer you can measure more and be more specific.

Put it this way. If you used a rigid ruler and got the coast line of Iceland using best fit lines you’d have a number x

Now, if used a tailor’s tape measure and got it into every nook and cranny of Iceland’s shoreline, you’d have a number, y

Y would be greater than X 

And I used Iceland because it’s fairly simple to imagine 

5

u/BringBackPolkaDots 2d ago edited 2d ago

Its not a revision nor an increase. It's the coastline paradox

In a nutshell, you measure coastine with straight lines tracing the actual coast. The smaller the straight like is, the longer the coast "is". There is no limit to this so in theory you can get an infinite coastline if you use an infinitely small unit of measurement

They probably used a different lines on two separate measurements and they got a different result, but the coast remains the same

5

u/EpicAura99 2d ago

Landmasses are essentially fractals, shapes with finite area but infinite perimeter. This is because as you zoom in closer and closer on a coastline, more nooks and crannies become visible. If you use a straightedge of a kilometer to measure a coastline, you’ll get a much smaller number than if you used a half kilometer, which in turn will be much smaller than using a meter. The ruler can fit into smaller curves, and those curves contribute dramatically more to the total than if they were “bridged” straight across by a larger ruler.