All of our data products are produced from weather satellites which have 1-2km^2 spatial resolution. In general, we offer 1km^2 resolution data in North & South America, Australia and eastern Asia, and 2km^2 data over Europe, Middle East, Africa and Western Asia.
The World API will use the latitude and longitude values you provide to interpolate to your location from the nearest points in our database. Our API database does not store all of the 1-2km^2 gridded data. Instead, we thin out these points to provide the greatest coverage over population areas and known areas of interest for solar development activity.
The typical distance to nearest point for ranges from 1 to 5km. The theoretical maximum distance, say for an unlucky place in the middle of the desert, well away from any population or electrical grid assets can be up to 25km.
If you believe these limitations are impacting the quality of the forecast at an area of interest for your application, you can choose to use our "Solar Radiation Sites" or "Utility Scale Sites" data products, which will place an exact location into our API database, dedicated to your site.