Tag Archives: data

TAFL — as a proper geodatabase

Update, 2017: TAFL now seems to be completely dead, and Spectrum Management System has replaced it. None of the records appear to be open data, and the search environment seems — if this is actually possible — slower and less feature-filled than in 2013.

Update, 2013-08-13: Looks like most of the summary pages for these data sets have been pulled from data.gc.ca; they’re 404ing. The data, current at the beginning of this month, can still be found at these URLs:

I build wind farms. You knew that, right? One of the things you have to take into account in planning a wind farm is existing radio infrastructure: cell towers, microwave links, the (now-increasingly-rare) terrestrial television reception.

I’ve previously written on how to make the oddly blobby shape files to avoid microwave links.  But finding the locations of radio transmitters in Canada is tricky, despite there being two ways of doing it:

  1. Wrestle with the Spectrum Direct website, which can’t handle the large search radii needed for comprehensive wind farm design. At best, it spits out weird fixed-width text data, which takes some effort to parse.
  2. Download the Technical and Administrative Frequency Lists (TAFL; see update above for URLs), and try to parse those (layout, fields). Unless you’re really patient, or have mad OpenRefine skillz, this is going to be unrewarding, as the files occasionally drop format bombs like
    never do this, okay?
    Yes, you just saw conditional different fixed-width fields in a fixed-width text file. In my best Malcolm Tucker (caution, swearies) voice I exhort you to never do this.

So searching for links is far from obvious, and it’s not like wireless operators do anything conventional like register their links on the title of the properties they cross … so these databases are it, and we must work with them.

The good things is that TAFL is now Open Data, defined by a reasonable Open Government Licence, and available on the data.gc.ca website. Unfortunately, the official Industry Canada tool to process and query these files, is a little, uh, behind the times:tafl2dbfYes, it’s an MS-DOS exe. It spits out DBase III Files. It won’t run on Windows 7 or 8. It will run on DOSBox, but it’s rather slow, and fails on bigger files.

That’s why I wrote taflmunge. It currently does one thing properly, and another kinda-sorta:

  1. For all TAFL records fed to it, generates a SpatiaLite database containing these points and all their data; certainly all the fields that the old EXE produced. This process seems to work for all the data I’ve fed to it.
  2. Tries to calculate point-to-point links for microwave communications. This it does less well, but I can see where the SQL is going wrong, and will fix it soon.

taflmunge runs anywhere SpatiaLite does. I’ve tested it on Linux and Windows 7. It’s just a SQL script, so no additional glue language required. The database can be queried on anything that supports SQLite, but for real spatial cleverness, needs SpatiaLite loaded. Full instructions are in the taflmunge / README.md.

TAFL is clearly maintained by licensees, as the data can be a bit “vernacular”. Take, for example, a tower near me:


The tower is near the top of the image, but the database entries are spread out by several hundred meters. It’s the best we’ve got to work with.

Ultimately, I’d like to keep this maintained (the Open Data TAFL files are updated monthly), and host it in a nice WebGIS that would allow querying by location, frequency, call sign, operator, … But that’s for later. For now, I’ll stick with refining it locally, and I hope that someone will find it useful.

Toronto Data really open

Looks like the data sets at toronto.ca/open might finally actually be open; that is, usable in a way that doesn’t bind subsequent users to impossible terms. The new licence (which unfortunately is behind a squirrelly link) basically just requires you to put a reference to this paragraph somewhere near your data/application/whatever:

Contains public sector Datasets made available under the City of Toronto’s Open Data Licence v2.0.

and a link to the licence, where possible.

Gone are the revocation clauses, which really prevented any open use before, because they would require you to track down all the subsequent users of the data and get them to stop. Good. I think we can now use the data in OpenStreetMap.

While commenting on the licence’s squirrelly URL — I mean, could you remember http://www1.toronto.ca/wps/portal/open_data/open_data_fact_sheet_details?vgnextoid=59986aa8cc819210VgnVCM10000067d60f89RCRD? — I stumbled upon the comedy gold that is the City of Toronto Comments Wall log. There goes my planned reading for the day.

Land Information Ontario – or, how I semi-accidentally ordered 3.5GB of terrain data

The Ontario Ministry of Natural Resources has a fairly well-hidden service that provides free geodata to the general public. One has to register with a sign and e-mail form, but there’s a large number of useful data sets available. The only disadvantage is that you can’t tell if your order will be delivered by download, or physically burnt to DVD and mailed from the MNR in Peterborough. The municipalities shown above were a download; the DEMs of my entire UTM zone? They’re in the mail …

free geodata for the numpty-about-Toronto

So if I want to learn some GIS skills, it would be helpful if I had some data to work with. Here are two data sources I have slight familiarity with:

toronto.ca | Open

Shapefiles, comprising:

The mixed map projections are a bit of a pain, and there are reports that some of the data is skewed from the rest of the Canadian data, but there’s much to love about this data.

GeoGratis, from Natural Resources Canada

An absolute tonne of data, in vector and raster formats. Services I’ve used are CanVec (vector data covering almost every feature) and Toporama (raster topographic maps; it has an associated Toporama Web Map Service).