Runtime heightmap fetching from a website that provides heightmap terrain data

[JoshuaLim007]

This is free! Awesome! Collecting heightmap data from real world

1. Use https://www.nextzen.org/
2. Create API key from https://developers.nextzen.org/
3. Use API key to fetch terrain data
4. Look at https://developers.nextzen.org/about.html for data fetching

Notes:

• https://tile.nextzen.org/tilezen/terrain/v1/{tilesize}/terrarium/{z}/{x}/{y}.png?api_key=your-nextzen-api-key
• x,y coordinates are not longitude and latitude, figure out how to map x,y to real world location, or rather figure out how to convert real world coordinates in latitude and longitude to x,y
• z is the scale of image fetched. 0 = the entire world, 1 = some amount of zoom, 2 = more zoom ... up to 13 or so
• x,y ranges from 0->2^z - 1 in integer
• height of terrain is = (red * 256 + green + blue / 256) - 32768 of the texture fetched. According to https://www.mapzen.com/blog/elevation/