This market resolves YES if a nuclear weapon is detonated in or above Greater London.
If a nuclear weapon does not hit London, then I will check the first 42 digits of the MNIST beacon, mod 100, for the first beacon after this question closes, or another public fair source of randomness if that turns out to be a bad way to generate a public truly random number for whatever reason. If it is 0, I will resolve NO. Otherwise, I will resolve N/A. This means that, for this market, you should treat NO as if it is 100 times less likely to happen than it actually is.
For example, if your actual expected outcome is 0.01% YES, 99.99% NO, you should expect this to resolve with probabilities 0.01% YES, 0.9999% NO, 98.9901% N/A, which means that your price of a YES share should be ~1% (actually 0.99%).
Some other values, for calibration (using the formula YES' = YES/(YES + (1-YES)/100), where YES' is the price for this question, and YES is your actual probability):
0.02% YES => ~2% YES' (actually 1.96%)
0.05% YES => ~5% YES' (actually 4.76%)
0.1% YES => 9% YES'
0.2% YES => 17% YES'
0.5% YES => 33% YES'
1% YES => 50% YES'
2% YES => 67% YES'
5% YES => 84% YES'
10% YES => 92% YES'
20% YES => 96% YES'
50% YES => 99% YES'
100% YES => 100% YES'