Chris Henrick clhenrick

Postgis queries workshop

With this viewer you will have a sandbox space to try different PostGIS capabilities using several datasets. Change the SQL and press Control+S or Command+S and check the results on the map on the right.

You can also play with the styles on the CartoCSS pane.

Editing OSM Boundaries

It's OSM best practice to have boundary=administrative on the constituent ways of a boundary relation, even if the same information is on the country's boundary relation. See http://wiki.openstreetmap.org/wiki/Boundaries and http://wiki.openstreetmap.org/wiki/Relation:boundary
However, the OSM default style only renders borders from relations, so a lot of OSM contributors don't know that the tags on the ways are missing.
Admin_level 2 boundaries on relations (probably no gaps) http://overpass-turbo.eu/s/hcO
Admin_level 2 boundaries on ways (zoom in and look for gaps) http://overpass-turbo.eu/s/hcN

##Task:

Color ramps: *-fill

Basic usage

marker-fill: ramp([column_name], colorbrewer(Greens));
                  |                    |
                  v                    |
      column to calculate ramp         |
                                       v

Processing JSON using jq

jq is useful to slice, filter, map and transform structured json data.

Installing jq

On Mac OS

brew install jq

Parse and append an HTML or SVG string. I use it a lot for appending a template, instead of generating it with d3.

d3.select('.container').appendHTML('<div><svg><g><rect width="50" height="50" /></g></svg></div>');

Unlike using .html, .appendHTML can append multiple elements

d3.select('.container').html('<span id="a"></span>');
d3.select('.container').html('<span id="b"></span>'); // will replace content
d3.select('.container').appendHTML('<span id="c"></span>'); // will append content

Color ramps: *-fill

Basic usage

marker-fill: ramp([column_name], colorbrewer(Greens));
                  |                    |
                  v                    |
      column to calculate ramp         |
                                       v

This Python script utilizes the GeoPy geocoding library to batch geocode a number of addresses, using various services until a pair of latitude/longitude values are returned.

https://gist.github.com/rgdonohue/c4beedd3ca47d29aef01

	import sys
	import urllib
	import urllib2
	import json
	import requests

	# Start a new batch SQL task
	def cartoBatchQuery(username, api_key, sql):
	r = requests.post('http://%s.cartodb.com/api/v2/sql/job?api_key=%s' %(username,api_key),
	headers={'content-type':'application/json'},

	<html>
	<head>
	<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet/v1.0.0-rc.1/leaflet.css" />
	<script src="http://cdn.leafletjs.com/leaflet/v1.0.0-rc.1/leaflet.js"></script>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/0.5.0-alpha2/html2canvas.min.js"></script>
	<script src="https://cdn.rawgit.com/flozz/StackBlur/master/dist/stackblur.min.js"></script>
	<script src="https://code.jquery.com/jquery-2.2.3.min.js"></script>
	<style>
	html, body {
	margin:0;

	<html>
	<head>
	<meta charset='utf-8' />
	<title></title>
	<meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
	<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
	<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.11.4/mapbox-gl.js'></script>
	<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.11.4/mapbox-gl.css' rel='stylesheet' />
	<style>
	body { margin:0; padding:0; }

Chris Henrick clhenrick

Postgis queries workshop

Contents

Editing OSM Boundaries

Color ramps: *-fill

Basic usage

Processing JSON using jq

Installing jq

On Mac OS

Color ramps: *-fill

Basic usage