How to use lineCap, lineJoin, setLineDash, lineDashOffset & miterLimit — Cartography might easily be considered the world’s most mature form of data visualization. Over the centuries, mapmakers have created and refined a sophisticated vocabulary of lines and symbols that convey relationships between objects and places. We can learn from their efforts. From blobs of blue, to “x” marks the spot…

How an experimental technology can save the day — For a while now, I’ve been developing a browser-based Earth mapping system using JavaScript and HTML canvas. One of the key challenges of this work has been keeping the user interface responsive while projecting 3D latitudes/longitudes onto a 2D canvas. Every point of every feature on the map must be…

The unlikely trio MUST, SHOULD, and MAY in internet standards — In March of 1997, Scott Bradner penned a short memo titled “Key Words For Use in RFCs to Indicate Requirement Levels”. It is more commonly referred to as simply RFC 2119. The entire document fits comfortably on two pages of paper. That memo would go on to become the single…

The World Wide Web’s hypertext markup language (HTML) has an inherent beauty all its own: Both the author’s words and the typographer’s instructions are contained in a single plain text file. Instructions are encoded using short, easily remembered mnemonics. Mnemonics are wrapped into pairs of less-than/greater-than tags which are easily…

Accuracy · Usability · Safety · Compliance — Every once in a while we come across a truly delightful piece of software: one that lets us accomplish something significant, that’s intuitively clear to operate, that safely and privately handles our needs, and that complies with industry standards and legal requirements. We can easily recognize the excellent quality of…

The classic, brilliant PNPOLY algorithm that dates back to 1970 — W. Randolph Franklin’s “point inclusion in polygon” algorithm weighs in at just seven lines of C code. It’s intuitively easy to understand, yet fast enough to work with sophisticated GIS datasets. It’s one of those gems that every advanced programmer should know. This article demonstrates how to use Franklin’s PNPOLY…

Choosing the right approach to personal data versus big data — This world is being assembled, in bits and pieces, from our interactions with technology: the tracking and surveillance of our movements; the communications and transactions of our commerce; the words and pictures of our inner circle; the desires and fears of our search for knowledge; and even the patterns and…

Correctly configuring CORS for content-type: application/json — The use of dynamic requests to backend servers is prevalent in modern web applications. Despite its commonplace nature, there are some gotchas that trip up even experienced developers. TL;DR In order to successfully preflight a JSON-encoded request to a different domain, the browser’s fetch request must include the HTTP header access-control-request-headers…