Mike Treglia mtreg

Interpolate points along lines using QGIS virtual layers

Suppose we want to interpolate a number of points along each line in a layer:

We have a column called stations that specifies how many points to interpolate on each line:

NYC had an import of over 1 million building footprints and 900,000 addresses in 2014 from the New York City Department of Information Technology and Telecommunications (DoITT). The DoITT GIS releases an updated shapefile of the footprints every quarter, and the latest version can be accessed here: Building footprints | Address points

Open datasets like these are a great opportunity to explore how OSM can be used as a bridge between authoritative information and that crowdsourced by citizens. Two years after the import, it is interesting to see how the OSM data compares with the latest official footprints. The interesting questions to ask is:

What has improved in the DoITT footprints that can be updated in OSM?
What has

Change your database RDS instance security group to allow your machine to access it.
- Add your ip to the security group to acces the instance via Postgres.
Make a copy of the database using pg_dump
- $ pg_dump -h <public dns> -U <my username> -f <name of dump file .sql> <name of my database>
- you will be asked for postgressql password.
- a dump file(.sql) will be created
Restore that dump file to your local database.
- but you might need to drop the database and create it first
- $ psql -U <postgresql username> -d <database name> -f <dump file that you want to restore>

the database is restored

	fast_extract <- function(x, y, ...) {
	## BEWARE no extract options are respected
	raster::extract(x, sfpoly_cells(x, y))
	}

	sfpoly_cells <- function(rast, sfpoly) {
	## BEWARE, could be a big-data, this is not
	## sparsely specified, so it's wasteful on memory, but fast (if you have the mem)
	which(!is.na(fasterize::fasterize(sfpoly, rast)[]))
	}

	# -- coding: utf-8 --

	"""
	/***************************************************************************
	Name : XYZ manager
	Description : Script to save/load/wipe WYZ sources in QGIS 3.0
	Date : February 27, 2017
	copyright : (C) 2017 by Thomas Gratier
	email : thomas.gratier@webgeodatavore.com

	library(tidycensus)
	library(tmap)
	library(tmaptools)
	library(sf)
	library(tigris)
	library(magick)
	library(tidyverse)
	options(tigris_use_cache = TRUE)

	ctys <- c("Dallas", "Tarrant", "Collin County", "Denton",

	CREATE TABLE public.testpolygons1
	(
	gid serial PRIMARY KEY,
	geom geometry(Polygon,3857)
	);

	CREATE TABLE public.testpolygons2
	(
	gid serial PRIMARY KEY,
	geom geometry(Polygon,3857)