Improving libgweather Locations
This page describes the process for improving the set of locations known by libgweather.
What's in it
libgweather contains information about:
- major cities in each country
- timezones for those cities as well as countries
- weather stations, attached to airports
For cities which aren't in the list, and if you're connected to the Internet, libgweather also uses OpenStreetMap's Nominatim service to search for locations.
Look for a file called Locations.xml on your computer, or download the latest version, to check whether your city, weather station/airport, or timezone is already in there.
What do we want in libgweather
Ideally, libgweather would contain a list of all the more important cities in each country, with a weather station/airport near it listed, so that accurate weather can be fetched, and timezone or world clocks configuration can be done offline, without the need to resort to online databases.
If you live in a specific country, you can probably better understand the expectations of users of that country when it comes to having their nearest "big city" listed. We usually prefer to only list cities with at least 100 thousand inhabitants, but it's not a hard limit when it makes sense.
You've already looked in the Locations.xml file, and in the project's Issues and Merge Requests, and the timezone is incorrect, the weather can't be fetched, or your city isn't listed.
First, try to find if something changed. For example, the country's timezone changed recently, or an airport closed, and collect those references. Our go-to reference is usually Wikipedia, because it usually references sources either in English or other languages.
Possible references are:
All done? Onto the next part
I don't know XML, I don't have time
Simply tell us about the problem, and give us as much information as possible in a new Issue. Make sure to include links to explanation if at all possible. It's easier for you to know that a city is misnamed if you live there, but we want to be sure we're not making mistakes, because that would be quite frustrating.
I know XML at least a little
If you know git, you probably know how to contribute Merge Requests and all that, so carry on to the next section.
For the others, open the text file editor. Once you've made your changes to the file, you'll need to change:
- the first line of the commit message to "locations: [summary of the changes]"
- on the subsequent lines, add more explanation if any is needed, and all the links to justify your change
- choose a descriptive name for the "Branch name". We usually prefer lower-case names with no spaces.
And click "Commit changes". Congratulations on making libgweather better!
Potential problems with changes
We run a battery of automated tests on changes made to the Locations.xml file, to avoid problems on the more than 8000 locations it contains. Here's a list of potential problems we might run into:
- the city is too small. If it has less than 100 thousand inhabitants, we might want to accept it anyway if it is the capital of a state/region in the country, and no bigger cities are around that people would usually search for.
- the airport is too far from the city. We have the coordinates for both the city and a number of airports. If there's no airport listed, we'll try to find the closest one in the same country. This is useful if you have 2 big cities close to each other, but a shared airport.
- the weather station doesn't transmit data to the weather service we use. Don't worry about it, include the airport, and we'll figure it out.
the coordinates are invalid. libgweather expects the coordinates to be decimal, with a space separating them. On most Wikipedia pages, there will be a link to the GeoHack website which will have the decimal value. Don't forget to remove the "," and make sure you copied the "-" signs if they're there!
Other than that, if in doubt, include the information you're unsure about, and look around in the file for examples.
Want to help more? Pick a country, one you know well would be best, and look at the definitions.
- Is every city name correct? (ie, it's the real name of a real city which is actually in that country, not some other country.)
- For cities known by multiple names:
- If the city is known by a different name in English than it is locally, is it listed by its English name, with a comment indicating the local name?
If the city is known by multiple names locally, are there comments indicating the other local names? (Note that we're mostly only interested in local names; it's generally not interesting to have comments giving alternative foreign names for the city, except in the case of cities like Gdańsk/Danzig or Kaliningrad/Königsberg that have very conspicuously changed names over the centuries.)
- For cities with multiple local names but no English-specific name, are we using the right local name as the "English" version? (Eg, since our dataset has both Finnish and Swedish names for many cities in Finland, we have to explicitly tell it to use the Finnish names. There may be other countries that have this problem as well.)
Likewise, for countries that are divided into <state>s, are the <state> names correct? (Basically all the same issues as the city names above apply here.)
Also, are all cities in the correct <state>?
One known bug with the handling of <state>s: we can't currently deal with cities that are considered to be their own state-level entities (eg, Beijing, China or Berlin, Germany); For now, those cities need to be placed inside imaginary <state>s of the same name. This will eventually be fixed.
- Is the use of transliteration / diacritic marks correct and "good"? In some cases we're stripping out diacritic marks to make the names more English-like. (Eg, the source dataset has all sorts of macrons and hooks and stuff in its transliterations of Arabic names, so that "Riyadh" beomes "Riyāḑ", etc. We flatten those back down to ASCII.) It might be the case that in some countries we're stripping out diacritics that we should be leaving there. (Or vice versa, maybe we're leaving in diacritics that should be skipped in the English versions?)
And onto the harder stuff:
- Does each city and each weather station location have the correct coordinates?
- Cities are easy (but time-consuming) to verify; just search for the coordinates in Google Maps. (The coordinates listed don't need to be the exact coordinates of the city center, just something reasonably close.)
- Weather stations are harder; if the weather station is an airport, you can often tell that the coordinates are correct because you can see the airport's runways in the Google Maps satellite view. Other than that, if the station is named after a city or geographic feature, you can at least check that it really is near that feature. (In particularly egregious cases, you can tell that the coordinates must be wrong because they place the weather station in the ocean, or in the wrong country...)