Mapping Earthquake Data Coding Challenge

On Friday Simon finished another beautiful Daniel Shiffman coding challenge called Mapping Earthquake Data. The purpose of this coding challenge was to visualize earthquake data from the USGS website ( by mapping the latitude, longitude and the magnitude of earthquakes with p5.js. The map imagery is pulled from mapbox.js and the math demonstrated coverts latitude, longitude to x,y via Web Mercator (the de facto standard for web mapping applications).

In Web Mercator, the “world coordinates” are adjusted such that the upper left corner is (0, 0) and the lower right corner is (256, 256). To visualize a place on the map, its coordinates are calculated with the help of this crazy formula:

{\begin{aligned}x&={\frac {128}{\pi }}2^{\text{zoom level}}(\lambda +\pi ){\text{ pixels}}\\y&={\frac {128}{\pi }}2^{\text{zoom level}}\left(\pi -\ln \left[\tan \left({\frac {\pi }{4}}+{\frac {\varphi }{2}}\right)\right]\right){\text{ pixels}}\end{aligned}}

where λ is the longitude in radians and φ is latitude in radians.

Daniel Shiffman turned parts of the formula into a, b and c to make it easier to apply it within the code. The coordinates he got as the result should then be subtracted from the center of the screen. Simon first forgot to do that subtraction bit and his Shanghai ended up outside the screen, which caused a lot of tears. The next day, after a long search, he found the problem.

And his math tutor explained what logarithms are.




Mapping Earthquake Data Coding Challenge 17 Mar 2017 2

Mapping Earthquake Data Coding Challenge 17 Mar 2017


While Mom and sis were away on a ballet weekend to Amsterdam Simon and Dad reviewed some topography. Topography is one of the things Simon used to be completely obsessed with. When he was 5, he spent hours drawing political maps of whole continents and regions from memory. For example, he would sit down and draw the map of the Caribbean, the tiniest islands included. When he drew a map of Latin America on his Christmas card at school that year his teacher didn’t hang the card on the wall, together with everyone else’s cards, because Simon’s card “wasn’t about Christmas”.

We were wondering how much Simon remembered now, without having practiced any topography this year. Turned out he’s still standing strong:

And here is Simon when he was 5: