anchor.diff:  
   # Group Lightning
   
  -## Retrieve lightning observation [?provider={provider1,provider2}&locationWithin={lonTopLeft,latTopLeft,lonBottomRight,latBottomRight}&occurredFrom={startTime}&occurredUntil={endTime}]
  +## Retrieve lightning observation [?provider={provider1,provider2}&locationWithin={lonTopLeft,latTopLeft,lonBottomRight,latBottomRight}&occurredFrom={startTime}&occurredUntil={endTime}&startPosition={startPosition}]
   ## Retrieve lightning observation [?provider={provider1,provider2}&locationWithin={lonTopLeft,latTopLeft,lonBottomRight,latBottomRight}&occurredFrom={startTime}]
   
   #### Example
  -https://lightning.weather.mg/search?provider=NOWCAST&locationWithin=[-10,80],[10,5]&occurredFrom=2017-01-05T12:21:14Z&occurredUntil=2017-01-05T12:21:15Z
  +https://lightning.weather.mg/search?provider=NOWCAST&locationWithin=[-10,80],[10,5]&occurredFrom=2017-01-05T12:21:14Z&occurredUntil=2017-01-05T12:21:15Z&startPosition=30000
   https://lightning.weather.mg/search?provider=NOWCAST&locationWithin=[-10,80],[10,5]&occurredFrom=2017-01-05T12:21:14Z
   https://lightning.weather.mg/search?provider=NOWCAST&locationWithin=[-10,80],[10,5]
   
   ##### Limitation
  -AWS Lambda service response can have size < 6MB
  +AWS Lambda service response can have size < 6MB, it is about 30000 lightning events. If there are more than 30 000 results in storage which comply to the search criteria, they can be retrieved using pagination, by the use of startPosition parameter. In such case response contains Link header with the next startPosition offset.
   If locationWithin is worldwide [-180, 90][180, -90] and occurrence ~3 days
   
   ### Observed lightning for a given boundingBox and time period
  
positive.code:     + occurredUntil: `2017-01-05T12:21:15Z` (end time range, optional)
          - time range period for lightning observation.
  
  
      + provider: `ENGLN,NOWCAST' (string, required)
          - lightning providers.
  
  
  
  + Response 200 (application/json)
  
negative.code: https://lightning.weather.mg/weighted?&temporalResolution=PT15M&spatialResolution=0.5&locationWithin=[-10,80],[10,5]&occurredFrom=2017-01-05T12:19:14Z
  https://lightning.weather.mg/weighted?&temporalResolution=PT15M&spatialResolution=0.5&locationWithin=[-10,80],[10,5]
  
  ##### Limitation
  Since AWS API Gatewey has maximum response time 30 seconds and a Lambda instance can allocate no more than 1.5Gb RAM it is impossible to process a really huge amount of lightning events. Therefore at most 200 000 first lightnings are being taken into account.
  
  ### Observed weighted lightning for a given boundingBox, time period, weighted by time span and spatial resolution
  
  This resource provides data from existing lightning observation providers.
  