When designing an iap, ICAO requires various 'extra' factors to be considered when calculating the minima eg terrain clearance in the missed approach area, type of approach and runway lighting.
Many people don't know this and just base their minima on the 'lowest possible' for that type of approach.
For instance, many years ago I got out the ICAO manual and tried to design an NDB/DME procedure for runway 26 (now runway 25) at Blackbushe. Although the lowest permissible minimum for this type of iap would be 250ft QFE, the minima taking all other required factors into account came to 620ft QFE.