Knowledge Base

FAQ & Knowledge Base

How does OpenUV API work?

The clear sky UV Index at sea level is first calculated from the solar zenith angle (SZA) and from ozone forecast fields and based on a math model firstly published by The National Institute of Water and Atmospheric Research (NIWA) of New Zealand. The raw UV Index then factored by elevation (optional) and sun-to-earth distance.

The ozone level data is based on global near-real-time OMTO3e product from OMI Instrument installed on AURA Satellite, NASA.

Fitzpatrick Skin Types & Safe Exposure Time Calculation

The most commonly used scheme to classify a person’s skin type by their response to sun exposure in terms of the degree of burning and tanning was developed by Thomas B. Fitzpatrick, MD, PhD. As a meter of fact even the skin color of Emoji characters based on the Fitzpatrick scale.

How to get UV Index for a specific time?

Use the dt request parameter to obtain estimated UV Index value for any point in time (hours, days, months, years). Please note, if there is no ozone level provided estimated UV Index will be based on a current Ozone level from OMI dataset. For 30 minutes intervals UV Index Forecast for any date use the UV Index Forecast method.

Why do I need to provide elevation from my client side?

In common UV levels increase by 4% for every 300 metres. Though the elevation could be explicitly identified by (lat, lng) using Google Maps API on OpenUV server side we chose to delegate that task to our clients due performance and Google Maps API limitation reasons (2,500 req/daily from one IP Address). Please reference the official Google Documenantion for how to obtain elevation from Google Maps API.

As service will grow we plan to implement elevation datasets available as a part of OpenUV API.

How often is Ozone data updated?

On average, the Ozone Monitoring Instrument (OMI) products available on EOSDIS NASA FTP portal within 3.5 hours after the observation time. Ozone data for a specific location is cached on our servers for 1 hour.

Cloud Effect on UV Radiation Index

There is a bunch of cool things you could do with raw UV Index value in your app, for instance show time to burn based on user's skin type obtained from Apple Health Kit or keep track of UV Index exposure and calculate Vitamin D intake. Check the Knowledge Base and Code Samples pages for more ideas how to use UV Index in your apps.

On average clouds absorb UV radiation, reducing ground-level UV intensity:

Clear skies allow virtually 100% of UV to pass through

Scattered clouds transmit 89%,

Broken clouds transmit 73%,

Overcast skies transmit 31% (see source).

Ultraviolet Radiation Reflection from Surfaces

Highly reflective surfaces can increase surrounding levels of solar UV including concrete, snow, glass, water and polished metals (see source).

Vitamin D and UV Radiation

Vitamin D is a hormone that controls calcium levels in the blood. It is needed to develop and maintain healthy bones, muscles and teeth and is also important for general health. The human body can get vitamin D in two ways: diet or sun exposure.

Minutes for sunlight exposure for sufficient Vitamin D intake (see source):