Du Analytics Lab is a set of free site-analysis tools built by Daniel Du. It has no server of its own: its pages are static files, your browser does the analysis, and it asks public data services for what it needs. This page lists which services, what each one is sent, what your browser keeps, and the licence and credit for every source of data.
The short version
The address you type goes to Photon, a public address-search service, so that it can suggest matches.
When you choose a site, its coordinates go to the public map-data and open-data servers listed below, to fetch what is around it.
This site sets no cookies and has no analytics, advertising or tracking. It never asks where your device is.
Reports (PDF) are made in your browser. They are not uploaded anywhere.
The site keeps some saved answers and one setting in your browser, so that coming back is fast. They are listed below.
What leaves your browser
Your browser sends each of these requests itself, straight to the service named. None passes through a server of ours. Like any web server, each service also sees your IP address and your browser's type; this site cannot prevent that, and each service has its own privacy terms.
Address search photon.komoot.io
Sent
The text in the address box, once you have typed at least three characters and paused for a moment, so a partly typed address is sent too. With it goes a fixed point in downtown Toronto, which makes nearby places rank first. It is not your location: this site never asks for it. Photon is a public search service run by komoot.
When
Whenever you search for an address, on any page.
Map data overpass-api.de and overpass.kumi.systems
Sent
A query for the OpenStreetMap streets, footpaths, buildings, businesses and stops around the site. It holds the site's coordinates and a search distance. In Competitor Density it also holds a brand or business name if you type one. If the first server is slow, the same query goes to the second as well.
When
Site Reach, and the walking and driving areas in Demographics; the building outline in Site Constraints; the walking index in Pedestrian Activity; Competitor Density's brand and name searches, and its categories where the data files built into this site do not cover the site; Drive-By Visibility where those files do not cover the site.
City of Toronto and TRCA map layers gis.toronto.ca and services1.arcgis.com
Sent
The site's coordinates, as a box reaching about 500 m out from the site, for each layer being checked, and a request for each layer's name to confirm it is still the layer expected. The second address is TRCA's ArcGIS Online account.
When
Site Constraints. Site Reach also asks for the same layers in the background while it works, so that Site Constraints opens quickly afterwards. Only the layers that cover the site are asked; whether the site is inside the City or TRCA area is decided in your browser, from files on this site.
Map tiles tiles.openfreemap.org
Sent
Requests for the map style, tiles, fonts and symbols. The tile addresses show which part of the world your map is showing; the address you typed is not in them.
When
Whenever a map is on screen.
Satellite imagery server.arcgisonline.com
Sent
Requests for satellite image tiles of the area on screen, from Esri.
When
Only when you choose Satellite. The choice is remembered in this browser (see below), so the imagery is asked for again on your next visit until you choose Map.
This site's own files d-anieldu.github.io
Sent
Requests for this site's pages, scripts, fonts, images and data files. The data files (census, Toronto counts, businesses, building heights, boundaries) are split into map cells and requested by cell, so the host can tell which part of the region you looked at. When a page is opened from a link that carries a site (the ?at=…&q=… part of its address), the host receives that as part of the link, as any web server does. The site is hosted on GitHub Pages, and GitHub's privacy statement applies to those requests.
When
Every visit.
Your mail app mailto:
Sent
Nothing, until you press send in your own mail app. The "Email Daniel" buttons are ordinary links that open a message to danieljzdu@gmail.com with the subject "Inquiry: Development Analytics" and, if you have chosen a site, its address in the message, for you to change or discard.
What your browser keeps
Saved answers IndexedDB
Answers from the Overpass servers and from the City and TRCA map layers are saved for about a day, a limited number at a time, so looking at the same site again is instant. They are map data for the sites you looked up, and each is filed under the coordinates of its site. Which Overpass server was slow or out of date is remembered for half an hour.
Your map choice localStorage
One item, named basemap, holds Map or Satellite.
Copies of this site's files service worker
A small program in your browser (a service worker) keeps copies of this site's own pages, scripts, fonts, images and data files, so that visits after the first load faster and a page you have opened before still opens offline. It handles only files from this site. Requests to the services above never pass through it.
The web address
The site you choose is written into the page's address, as ?at=latitude,longitude&q=address, so that every tool opens the same site and a link can be shared. It also goes into your browser history. Anyone you send that link to sees the address.
To remove all of this, clear the site data for d-anieldu.github.io in your browser's settings.
Cookies and tracking
This site sets no cookies. It has no analytics, advertising, session recording, social-media buttons or tracking pixels, and it loads no script, font or image from another website: the fonts are served from this site. It has no accounts and no form that sends anything to a server of ours, and it does not ask for your device's location.
Data sources, licences and credits
Each source is used under its own licence, and is credited as the licence asks. Reports print the credit for the sources they used, with the product and date.
OpenStreetMap
Used for
Streets, footpaths, buildings, businesses and transit stops: the network every travel time is measured on, the businesses counted and the buildings that block a view. It is read live from the Overpass servers, and from a daily copy of Ontario's map data (from Geofabrik) that is cut into files when the site is built. It is edited by volunteers and can be incomplete or out of date.
Address search. Photon searches OpenStreetMap data, so its results carry the OpenStreetMap credit above. Its terms ask for fair use: heavy use is throttled, and there is no guarantee that it is available.
City of Toronto Open Data
Used for
Pedestrian and vehicle counts at intersections (Traffic Volumes at Intersections for All Modes), building heights (3D Massing), the city boundary, and the City's map layers checked by Site Constraints: the Ravine and Natural Feature Protection By-law, Environmentally Significant Areas, the Natural Heritage System, Provincially Significant Wetlands, the Provincial Greenbelt, the Heritage Register and Heritage Conservation Districts, basement flooding study areas and hydro corridors.
Licence
Open Government Licence – Toronto.
Credit
Contains information licensed under the Open Government Licence – Toronto
Toronto and Region Conservation Authority (TRCA)
Used for
The regulatory floodline and the regulation limit checked by Site Constraints, and the TRCA area that decides whether they apply.
Licence
TRCA Open Data Licence v 1.0.
Credit
Contains information made available under the Toronto and Region Conservation Authority (TRCA)'s Open Data Licence v 1.0
Statistics Canada
Used for
The 2021 Census of Population (its profile, geographic attribute files and boundary files), July 1 population estimates and a table of mortgage rates. They feed Demographics and the resident counts in Pedestrian Activity.
Licence
Statistics Canada Open Licence.
Credit
Adapted from Statistics Canada, [name of product], [reference date]. This does not constitute an endorsement by Statistics Canada of this product.
Canada Mortgage and Housing Corporation (CMHC)
Used for
The Rental Market Survey, the Starts and Completions Survey and the rented condominium tables: rents, vacancy and new housing supply in Demographics.
Credit
Adapted from Canada Mortgage and Housing Corporation, [name of product], [reference date]. This does not constitute an endorsement by Canada Mortgage and Housing Corporation of this product.
Ontario Ministry of Finance
Used for
The Ontario Population Projections by census division, in Demographics.
Licence
Open Government Licence – Ontario.
Credit
Contains information licensed under the Open Government Licence – Ontario
Esri World Imagery
Used for
The Satellite map, only when you choose it.
Credit
Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community
Who runs this
Du Analytics Lab is built by Daniel Du, University of Waterloo, in a personal capacity. It is not an official statement of the University of Waterloo. Every result is informational screening, built on modelled estimates and public data, and is not professional advice; each report ends with the full notice.
Questions, corrections, or a property to discuss: danieljzdu@gmail.com. An inquiry is a plain email. The "Email Daniel" buttons only open your own mail app with a message already written; there is no form, no booking link and no tracking behind them, and this site does not see what you send. Daniel's development analytics work is at d-anieldu.github.io/du-analytics.
Next step
Development Analytics
Lot-level evidence for Toronto zoning applications and hearings at the Committee of Adjustment, TLAB and the OLT: every lot nearby measured, every source cited.