How is the index price calculated

Each index price is computed based on order book data from a number of spot exchanges. The calculation has four steps: 

1. Obtain a list of prices from the relevant exchanges. The price from an exchange is calculated as the average of best bid and ask in the order book. 
2. Calculate the median of available prices. 
3. Cap each price to deviate at most 0.5% from the median. 
4. Calculate the simple average of capped values to obtain the index price.