Canadian Postal Data:FAQ
From Melissa Data Wiki
- What does this data consist of?
- This data consists of a Record ID, Postal Code, Shape (WKB), and WKT (well-known text).
Well-Known Text (WKT)
- What is Well-Known Text (WKT)?
- WKT is the Open Geospatial Consortium(OGC) standard for spatial data. This represents the vector geometry of the postal codes. The postal code shapes will either be a MultiPolygon or a Polygon.
MULTIPOLYGON (((40 40, 20 45, 45 30, 40 40)), ((20 35, 10 30, 10 10, 30 5, 45 20, 20 35), (30 20, 20 15, 20 25, 30 20)))
POLYGON((-122.358 47.653, -122.348 47.649, -122.348 47.658, -122.358 47.658, -122.358 47.653))
- What is Shape?
- Shape is in Well-Known Binary (WKB) format that can be used within SQL Server’s built in geography functions. Well-known binary will be in hexadecimal as a geography instance (Not geometry).
How to Use Data
- How do I use this data?
- To utilize this data, you require Geospatial tools for GIS, mapping, and data visualization. You can programmatically use the data to cater to your business needs with any language that supports Geospatial tools and/or Database Engines that have built-in libraries that can manipulate Geospatial data.
- How good is your data?
- Our data or polygons were generated with verified address geo coordinates. We only included verified addresses as the outer bounds of the polygons. We are currently using Canada Post data to create these polygons.
- How accurate can I expect your data to be?
- The level of accuracy will vary from each postal code range depending on the coverage available from Canada Post. Generally, you will see that the shapes are an accurate representation of the postal codes, while some may represent a convex hull. There may be some shapes that do not include highways, parks, or streets. This occurs because we are using address geo coordinates to generate the shapes. Additionally, there are some postal codes that may not fully developed, and this may occur because there are not enough data points that are available within that specific area.
Comparison to Competitors
- How do you compare against your competitors?
- We believe we are slightly above average in comparison to our competitors. We are still working on getting more coverage for Canadian Geocoordinates, and we will continually update the data to provide the best quality information. We do not use crowd sourced systems, but instead use verified address rooftop geo coordinates to generate these shapes. The difference would be measured by the data sources and the algorithms used to generate these shapes.
- How precise is your data?
- We use verified address geo coordinates to create the outer bounds of the polygons. There may be some areas that are missing from the actual polygon. The methodology used to create these polygons generates more precise shapes with verified rooftop geo coordinate data. Due to the shapes being created with rooftop information, there may be some areas of the polygon that should be included. For example, streets, parks, and highways will generally not be included within these polygons. We base our shapes off of validated information, and are using that to create the outer bounds of the shapes.
- What are the thresholds for error, if any?
- The thresholds would be with the individual address being utilized to create geo coordinates. We may omit streets, parks, and highways that do not have an address. This is one of the reasons why you may see more multipolygons within the data. For this reason, we may see polygons that should be larger to cover the full boundaries of the postal codes.
Data Sources and Generation
- What is your data source and how did you generate the data?
- We have generated this data using Canada Post data. This data was generated to fit the Industry standard to make it easier to manipulate. This data includes WKT to ensure flexibility for all our customers. To generate these polygons, we used GIS tools to create these polygons based upon the rooftop geo coordinates. The algorithms are designed to get the outer bound points of each postal code to create the polygons.
Not Matching Google Maps
- Why does your polygon not match google maps?
- Google maps may have different data points to generate these polygons. In many cases, you may see that our shapes have significantly more vertices. There will be some polygons that are extremely similar to Google Maps, while some are completely different. Google’s shapes have more rounded edges and their data sources could be either similar or completely different from our data.
- Why are there multipolygons?
- The multipolygons are created because individual addresses are used to create the outer bounds of the polygons. These shapes are sometimes separated by streets, bodies of water, parks and highways. There may be some instances where this is not the case, but generally these shapes will be multipolygons if the postal codes are separated by streets or highways.
Canadian Postal Code Counts and Missing Postal Codes
- How many postal code are there in Canada and why is there some postal code polygons missing?
- Canada Post may not have the Rooftop level geo coordinates for specific postal codes or for individual addresses. Also, some areas of postal codes are less developed than others, which is why there may be some postal codes that do not have any information. We are continuing to improve our coverage.
Outside of Bounds Address
- I found an address with a postal code that lies outside of your postal code polygon, why did this happen?
- This may occur depending on the level of coverage for the specific postal code in question. There may be instances where the polygon does not encompass the full postal code. The coverage rate for the polygons will generally hold a majority of verified addresses. There may be some postal codes that does not have great coverage.
Polygon Shape Differs
- Why does your polygon shape differ from other vendors or sources? Which is correct?
- We use verified addresses as the outer bounds of the polygon. Some other vendors may use different data sources and algorithms to create these shapes. We use verified Rooftop geo coordinates to create the shapes. Some sources may be interpolated data, the source of data could be different, or the methodology for generating these shapes could differ.