Chris Henrick clhenrick

The difference between XYZ and TMS tiles and how to convert between them

Lots of tile-based maps use either the XYZ or TMS scheme. These are the maps that have tiles ending in /0/0/0.png or something. Sometimes if it's a script, it'll look like &z=0&y=0&x=0 instead. Anyway, these are usually maps in Spherical Mercator.

Good examples are OpenStreetMap, Google Maps, MapBox, MapQuest, etc. Lots of maps.

Most of those are in XYZ. The best documentation for that is slippy map tilenames on the OSM Wiki, and Klokan's Tiles a la Google.

Raspberry Pi setup

Just wanted a quick start guide for myself so that I wouldn't have to keep rooting through Google to remember all this stuff. Hopefully it helps other people.

If you had other ideas or suggestions please leave a comment.

Useful things to own before you buy a Pi

The first time I bought a Pi I was enormously frustrated with myself because I didn't own all of this stuff. Kept having to order things off of Amazon and wait to get started... very irritating. This is all good stuff to have laying around anyway:

Installing CartoDB on Ubuntu Server 12.04

Get CartoDB Rails application source

sudo apt-get update

sudo apt-get install git

cd ~

git clone --recursive https://github.com/CartoDB/cartodb20.git

From http://concord-consortium.github.io/developer-notes/automating-gh-pages-integration.html:

How to setup a git repo so gh-pages automatically tracks commits to master and ‘git push origin’ updates the remote master and gh-pages branches.

Setup a test repo:

mkdir pages-test
cd pages-test/
git init .

Using pg.connect is the way to go in a web environment.

PostgreSQL server can only handle 1 query at a time per conenction. That means if you have 1 global new pg.Client() connected to your backend your entire app is bottleknecked based on how fast postgres can respond to queries. It literally will line everything up, queuing each query. Yeah, it's async and so that's alright...but wouldn't you rather multiply your throughput by 10x? Use pg.connect set the pg.defaults.poolSize to something sane (we do 25-100, not sure the right number yet).

new pg.Client is for when you know what you're doing. When you need a single long lived client for some reason or need to very carefully control the life-cycle. A good example of this is when using LISTEN/NOTIFY. The listening client needs to be around and connected and not shared so it can properly handle NOTIFY messages. Other example would be when opening up a 1-off client to kill some hung stuff or in command line scripts.

	<snippet>
	<content><![CDATA[<!DOCTYPE html>
	<!--[if lt IE 7]> <html class="no-js lt-ie9 lt-ie8 lt-ie7"> <![endif]-->
	<!--[if IE 7]> <html class="no-js lt-ie9 lt-ie8"> <![endif]-->
	<!--[if IE 8]> <html class="no-js lt-ie9"> <![endif]-->
	<!--[if gt IE 8]><!--> <html class="no-js"> <!--<![endif]-->
	<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
	<title>${1:Project Name}</title>

	/*
	You'll need something like this in your HTML:
	<script src="http://d3js.org/topojson.v1.min.js"></script>
	*/

	L.TopoJSON = L.GeoJSON.extend({
	addData: function(jsonData) {
	if (jsonData.type === "Topology") {
	for (key in jsonData.objects) {
	geojson = topojson.feature(jsonData, jsonData.objects[key]);

	<!doctype html>
	<html lang="en">
	<head>
	<meta charset="UTF-8">
	</head>
	<body>
	<div class="viewport"></div>

	<script src="//cdnjs.cloudflare.com/ajax/libs/three.js/r58/three.min.js"></script>
	<script src="//threejs.org/examples/js/controls/OrbitControls.js"></script>

	Handlebars.registerHelper( 'times', function( n, block ) {
	var accum = '',
	i = -1;

	while( ++i < n ) {
	accum += block.fn( i );
	}

	return accum;
	});

	<?php
	$ch = curl_init($_GET['url']);
	curl_setopt($ch, CURLOPT_HEADER, 0);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	$output = curl_exec($ch);
	curl_close($ch);
	echo $output;
	?>