Drew Silcock new Stream(consciousness)

Calculating meters per pixel from aerial photographs


Say you’re doing some aerial photogrammetry, for scientific purposes. Then you need to know those pernickety little details like the resolution that your pictures will produce, and the precision you can infer from this. This post shows how to calculate how many meters each pixel of a photo taken by a particular camera corresponds to, given the required information.

The trigonometry assumes that you are flying a UAV with the camera facing directly downwards. The example values given are those taken from the Canon Ixus 132 I am using for my aerial photogrammetry project.

Proper line numbers with Jekyll

By default, Jekyll uses the (excellent) Pygments syntax highlighter for code blocks. While this works well, the line numbers it produces are less than satisfactory.

Here’s the default lineno option, inline:


This works, but has two main visual and practical problems: 1. There is no visual separation between the line numbers and the code, causing them to visually become indistinct, and 2. When trying to copy code from the codeblocks, the line numbers are included, annoyingly.

So what’s the alternative?

Compiling zsh without root

This article describes how to compile zshell on a Linux machine without root, for instance when working remotely on a server on which you do not have root.

Coding cheatsheet

Here’s a load of quick snippets of easy-to-forget but often used commands, tricks and tips. It’s got useful info about git, Vim, Python and Perl.