Plotting the naval territory of a country

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    naval Plotting
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Discussion Overview

The discussion revolves around the challenge of generating a new border for a country that maintains a constant distance of 10 miles from the original border, represented as a polygon. Participants explore potential algorithms and methods for achieving this, considering both computational complexity and geometric intricacies.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about algorithms for creating a new border that is consistently 10 miles from the original polygon border, suggesting that the problem may be more complex than it appears.
  • Another participant proposes generating parallel lines for each straight segment of the polygon, noting the need to adjust for intersections and round corners to maintain the 10-mile distance accurately.
  • A different participant highlights the complexity introduced by geographical features, such as bays, which can affect the distance calculations significantly.
  • One participant mentions the concept of dilation from image processing as a potential method, suggesting the use of image libraries for manipulation if the map is in bitmap format.
  • Another participant clarifies that the borders would need to be represented as a set of coordinates, indicating limitations in the proposed image processing approach.

Areas of Agreement / Disagreement

Participants express varying perspectives on the complexity of the problem and the methods to approach it, indicating that there is no consensus on a single solution or algorithm.

Contextual Notes

The discussion reveals limitations related to the assumptions about the geographical features and the representation of borders, as well as the computational efficiency of the proposed methods.

jbunten
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OK, say we have the border of a country represented by a polygon, how do we obtain a new border which at every point has it's nearest point to the country at exactly say 10 miles from it?

Is there an algorithm to do this or is it highly computational?

It's not as simple as it first seems.
 
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If you have an equation for each straight line segment, you could generate a parallel line 10miles from it (have to get the sign right for =outside).
Then find the intersect fro each line segment with the next to cut them into a single polygon.
Might not be the most efficent and for a true 10mile limt you would have to round the corners where the line segments meet to a 10mi radius.

There is probably a well known aglorithm for this - try http://www.cgal.org/
 
That's what I thought, but the problem is far more complex, imagine a bay that goes very far inland (20mi for instance) then 10mi from that bay can be very near to another part of the island, the problem is deceptively complex.
 
Yes, it is tricky.
In image processing it's known as dilation, you use it to close up any gaps in an image and then erode back to the original size before doing operations like character recognition. If you have the map as a bitmap you can probably find an image library thatworks well (eg opencv?)
 
Hi, fraid not, they would have to exist as a set of coordinates.
 

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