NGeoNames

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Inspired by https://github.com/AReallyGoodName/OfflineReverseGeocode

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# ![Logo](https://raw.githubusercontent.com/RobThree/NGeoNames/master/icon.png) NGeoNames

Inspired by [OfflineReverseGeocode](https://github.com/AReallyGoodName/OfflineReverseGeocode) found at [this Reddit post](http://www.reddit.com/r/programming/comments/281msj/). You may also be interested in [GeoSharp](https://github.com/Necrolis/GeoSharp). Uses [KdTree](https://github.com/codeandcats/KdTree). Built and tested on .Net 4.5.

This library provides classes for downloading, reading and parsing, writing and composing [files from](http://download.geonames.org/export/dump/) [GeoNames.org](http://download.geonames.org/export/zip/) and provides (reverse) geocoding methods like `NearestNeighbourSearch()` and `RadialSearch()` on the downloaded dataset(s).

This library is available as [NuGet package](https://www.nuget.org/packages/NGeoNames/).

## Basic usage / example / "quick start"

```c#
var datadir = @"D:\test\geo\";

// Download file (optional; you can point a GeoFileReader to existing files ofcourse)
var downloader = GeoFileDownloader.CreateGeoFileDownloader();
downloader.DownloadFile("NL.zip", datadir);    // Zipfile will be automatically extracted

// Read NL.txt file to memory (NL = ISO3166-2:The Netherlands)
var nldata = GeoFileReader.ReadExtendedGeoNames(Path.Combine(datadir, "NL.txt")).ToArray();   
// Note: we "Materialize" the file to memory by calling ToArray()

// We're going to use Amsterdam as "search-center"
var amsterdam = nldata.Where(n => 
        n.Name.Equals("Amsterdam", StringComparison.OrdinalIgnoreCase) 
        && n.FeatureCode.Equals("PPLC")
    ).First();

// Initialize a reversegeocoder with our geo-items from The Netherlands
var reversegeocoder = new ReverseGeoCode<ExtendedGeoName>(nldata);
// Locate 250 geo-items near the center of Amsterdam
var results = reversegeocoder.RadialSearch(amsterdam, 250);  
// Print the results
foreach (var r in results) {
    Console.WriteLine(
        string.Format(
            CultureInfo.InvariantCulture, "{0}, {1} {2} ({3:F4}Km)", 
            r.Latitude, r.Longitude, r.Name, r.DistanceTo(amsterdam) / 1000d
        )
    );
}
```

## Overview

The library provides for the following main operations:

1. [Downloading / retrieving data from geonames.org](#downloading) (Optional)
2. [Reading / parsing geonames.org data](#parsing)
3. [Utilizing geonames.org data](#utilizing)
4. [Writing / composing geonames.org data](#composing)

The library consists mainly of parsers, composers and entities (in their respective namespaces) and a `GeoFileReader` and `GeoFileWriter` to read/parse and write/compose geonames.org compatible files, a `GeoFileDownloader` to retrieve files from geonames.org and a `ReverseGeoCode<T>` class to do the heavy lifting of the reverse geocoding itself.

Because some "geoname files" can be very large (like `allcountries.txt`) we have a `GeoName` entity which is a simplified version (and baseclass) of an `ExtendedGeoName`. The `GeoName` class contains a unique id which can be used to resolve the `ExtendedGeoName` easily for more information when required. It is, however, recommended to use `<countrycode>.txt` (e.g. `GB.txt`) `cities15000.txt` or `cities1000.txt` for example to reduce the dataset to a smaller size, You can also compose your own custom datasets using the `GeoFileWriter` and composers.

Also worth noting is that the readers return an `IEnumerable<SomeEntity>`; make sure that you materialize these enumerables to a list, array or other datastructure (using `.ToList()`, `.ToArray()`, `.ToDictionary()` etc.) if you access it more than once to avoid file I/O to the underlying file each time you access the data.

### <a name="downloading"></a>Downloading / retrieving data from geonames.org (Optional)

To download files from geonames.org you can use the `GeoFileDownloader` class which is, in essence, a wrapper for a basic [`WebClient`](http://msdn.microsoft.com/en-us/library/system.net.webclient.aspx). The simplest form is:

```c#
// Downloads (and extracts) geoname data in NL.zip from geonames.org
GeoFileDownloader.CreateGeoFileDownloader()
    .DownloadFile("NL.zip", @"D:\my\geodata\geo");
    
// Downloads (and extracts) postalcode data in NL.zip from geonames.org
GeoFileDownloader.CreatePostalcodeDownloader()
    .DownloadFile("NL.zip", @"D:\my\geodata\postalcode");
```

You can specify the BaseUri in the `GeoFileDownloader` constructor or just pass an absolute url to the `DownloadFile()` method if you want to use another location than the default `http://download.geonames.org/export/dump/`. The static 'factory methods'  `CreateGeoFileDownloader()` and `CreatePostalcodeDownloader` are the easiest way to create a `GeoFileDownloader`; these use the built-in values for the BaseUri. The `GeoFileDownloader` has properties to set a (HTTP) `CachePolicy`, `Proxy` and `Credentials` to use when downloading the file. The filedownloader, by default, downloads a file only if the destination file doesn't exist *or* when the destination file has "expired" (by default 24 hours). It uses the file's CreationDate to determine when the file was downloaded and if a newer version should be downloaded. The "TTL", how long a file will be 'valid', can be set using the `DefaultTTL` property of the `GeoFileDownloader` class. You can also use the `DownloadFileWhenOlderThan()` method which allows you to explicitly set a TTL. When a filename is specified (e.g. `d:\folder\foo.txt`) the file will be named accordingly.

ZIP files are automatically extracted in the destinationfolder; the original zipfile is preserved because the `GeoFileDownloader` needs to know which files are supposed to be in the zipfile and thus in the destinationdirectory in their extracted form.

### <a name="parsing"></a>Reading / parsing geonames.org data

Once files are downloaded using the `GeoFileDownloader`, *or* by using your own custom/specific implementation, the files can be accessed using the `GeoFileReader` class. This class contains a number of static "convenience methods" like `ReadGeoNames()` and it's "sibling" `ReadExtendedGeoNames()`. but also `ReadCountryInfo()`, `ReadAlternateNames()` etc. There is a "convenience method" for each entity.

```c#
// Open file "cities1000.txt" and retrieve only cities in the US
var cities_in_us = GeoFileReader.ReadExtendedGeoNames(@"D:\my\geodata\cities1000.txt")
        .Where(p => p.CountryCode.Equals("US", StringComparison.OrdinalIgnoreCase))
        .OrderBy(p => p.Name);
```

Again, **please note** that `Read<Something>` methods return an `IEnumerable<T>`. Whenever you want to access the data more than once you will probably want to call `.ToArray()` or similar to materialize the data into memory. The `GeoFileReader` class has two static method (`ReadBuiltInContinents()` and `ReadBuiltInFeatureClasses()`) that can be used to use built-in values for continents and [feature codes](http://www.geonames.org/export/codes.html) which are not provided by geonames.org as downloadable files. You can, however, craft your own files for this purpose and use the `ReadContinents()` and `ReadFeatureClasses()` if you want to specify your own values / update built-in values (should `NGeoNames`'s values be outdated for example).

You can also add your own entities and, as long as you provide a parser for it, use the `GeoFileReader` class to read/parse files for these entities as well:

```c#
var data = new GeoFileReader().ReadRecords<MyEntity>("d:\foo\bar.txt", new MyEntityParser());
```

As long as your parser implements `IParser<MyEntity>` you're good to go. A parser can skip a fixed number of lines in a file (for example a 'header' record), skip comments (for example lines starting with `#`) and you can even specify the encoding to use etc. Examples and more information can be found in the unittests.

Another thing to note is that the `GeoFileReader` will try to "autodetect" if the file is a plain text file (`.txt` extension) or a GZipped file (`.gz` extension). Support for GZip was added to keep the footprint of the files lower when desired. This will, however, trade-off I/O speed and CPU load for space. The `ReadRecords<T>()` method has an overload where you can explicitly specify the type of the file (should you want to use your own file-extensions like `.dat` for example).

> Support for compressing downloaded files using the `GeoFileDownloader` on the fly is planned for a later version; for now you will have to GZip the files manually.

The `GeoFileReader` also supports the use of [`Stream`](http://msdn.microsoft.com/en-us/library/system.io.stream.aspx)s so you can provide data from a MemoryStream for example or any other source that can be wrapped in a stream.

As you'll probably realize by now, the `GeoFileReader` class *combined* with [LINQ](http://msdn.microsoft.com/en-us/library/bb397926.aspx) allows for very powerful querying, filtering and sorting of the data. Combine it with the `GeoFileWriter` to persist custom datasets (custom "materialized views") and the sky is the limit.

### <a name="utilizing"></a>Utilizing geonames.org data

The 'heart' of the library is the `ReverseGeoCode<T>` class. When you supply it with either `IEnumerable<GeoNames>` or `IEnumerable<ExtendedGeoNames>` it can be used to do a `RadialSearch()` or `NearestNeighbourSearch()`. Supplying the class with data can be done by either passing it to the class constructor or by using the `Add()` or `AddRange()` methods. You may want to call the `Balance()` method to balance the internal KD-tree, however; this is done automatically when the data is supplied via the constructor. Even if you choose to store your data in a database or custom (binary?) fileformat or anything else; as long as you provide an `IEnumerable` to this class you'll be able to use it.

```c#
// Create our ReverseGeoCode class and supply it with data
var r = new ReverseGeoCode<ExtendedGeoName>(
        GeoFileReader.ReadExtendedGeoNames(@"D:\foo\cities1000.txt")
    );
            
// Create a point from a lat/long pair from which we want to conduct our search(es) (center)
var new_york = r.CreateFromLatLong(40.7056308, -73.9780035);

// Find 10 nearest
r.NearestNeighbourSearch(new_york, 10);
```

Ofcourse there's no need to dabble with lat/long at all:

```c#
// Read data into memory
var data = GeoFileReader.ReadExtendedGeoNames(@"D:\foo\cities1000.txt")
        .ToDictionary(p => p.Id);

// Find New York by it's geoname ID (O(1) lookup)
var new_york = data[5128581];

// Find 10 nearest
var r = new ReverseGeoCode<ExtendedGeoName>(data.Values);
r.NearestNeighbourSearch(new_york, 10);
```

Or simply find by name:

```c#
// Read data into memory
var data = GeoFileReader.ReadExtendedGeoNames(@"D:\foo\cities1000.txt")
        .ToArray();

// Find New York by it's name (linear search, O(n))
var new_york = data.Where(p => p.Name.Equals("New York City")).First();

// Find 10 nearest
var r = new ReverseGeoCode<ExtendedGeoName>(data);
r.NearestNeighbourSearch(new_york, 10);
```

Depending on how you want to search/use the underlying data you may want to use other, more optimal, datastructures than demonstrated above. It's up to you!

Note that the library is based on the [**International System of Units (SI)**](http://en.wikipedia.org/wiki/International_System_of_Units); units of distance are specified in **meters**. If you want to use the imperial system (e.g. miles, nautical miles, yards, foot and whathaveyou's) you need to convert to/from meters. The `GeoUtil` class provides helper-methods for converting miles/yards to meters and vice versa.

The `GeoName` class (and, by extension, the `ExtendedGeoName` class) has a `DistanceTo()` method which can be used to determine the exact distance betweem two points.

Both the `NearestNeighbourSearch()` and `RadialSearch()` methods have some overloads that accept lat/long pairs as *doubles* as well.

### <a name="composing"></a>Writing / composing geonames.org data

The `NGeoNames.Composers` namespace holds composers (the opposite of parsers) to enable you to write geoname.org datafiles. For this you can use the `GeoNameFileWriter` class which, like the `GeoNameFileReader` class, has generic methods for writing records (`WriteRecords<T>`) and static "convenience methods" to write specific entities to a file. If you wanted to 'transform' a file like `allcountries.txt` to a file with data from, say, the [Benelux](http://en.wikipedia.org/wiki/Benelux)) you could supply the `GeoNameFileWriter` with data from `BE.txt`, `NL.txt` and `LU.txt` *or* data from `allcountries.txt` or `cities1000.txt` filtered with a LINQ query to only data from these countries.

Below is an example of what this would look like (with an extra filter added to filter out records with `population < 1000`):

```c#
// Filter 'allcountries.txt' to only BE, NL, LU entries with a population of >= 1000
GeoFileWriter.WriteExtendedGeoNames(@"d:\foo\benelux1000.txt",
   GeoFileReader.ReadExtendedGeoNames(@"d:\foo\allcountries.txt")
      .Where(e => new[] { "BE", "NL", "LU" }.Contains(e.CountryCode) && e.Population >= 1000)
      .OrderBy(e => e.CountryCode).ThenBy(e => e.Name)
);

// ...or...

// Join BE, NL en LU datasets, filter records with a population of >= 1000
GeoFileWriter.WriteExtendedGeoNames(@"d:\foo\benelux1000.txt",
   GeoFileReader.ReadExtendedGeoNames(@"d:\foo\BE.txt")
      .Union(GeoFileReader.ReadExtendedGeoNames(@"d:\foo\NL.txt"))
      .Union(GeoFileReader.ReadExtendedGeoNames(@"d:\foo\LU.txt"))
        .Where(e => e.Population >= 1000)
        .OrderBy(e => e.CountryCode).ThenBy(e => e.Name)
);

```

### A word about "extended format"

The `GeoNamesReader` and `GeoNamesWriter` and the (Extended)GeoName parsers/composers always assume the `ExtendedGeoName` format (e.g. 19 fields of data) unless explicitly specified. The parameter **extendedfileformat** may pop-up on some method overloads; whenever this parameter is passed `false` the class will assume a 'simple' (or non-extended) format with only 4 fields of data: Id, Name, Latitude and Longitude. This format is more compact; especially when writing `GeoName` entities instead of `ExtendedGeoName` entities to a file. However, to remain compatible with the original files you probably don't want to use this 'simple' format. Make sure you understand the consequences before you do!

## Help

The [NuGet package](https://www.nuget.org/packages/NGeoNames/) comes with a Windows Help File (`NGeonames.chm`) with lots more information. You can also build this help file, or other formats, yourself using [Sandcastle Help File Builder](https://shfb.codeplex.com/). And finally you can use the richly commented code if you don't want to build or use help files.

## Project status

<img src="http://riii.nl/womm" width="200" height="200" align="left"> The project will be updated from time-to-time when required. I am happy to accept pull-requests; if you're interested in contributing to this library please contact me. If you have any issues please [open an issue](https://github.com/RobThree/NGeoNames/issues).

[![Build status](https://ci.appveyor.com/api/projects/status/mkmbxvm1w0mxaifv)](https://ci.appveyor.com/project/RobIII/ngeonames) <a href="https://www.nuget.org/packages/NGeoNames/"><img src="http://img.shields.io/nuget/v/NGeoNames.svg?style=flat-square" alt="NuGet version" height="18"></a>

## License

Licensed under MIT license. See [LICENSE](LICENSE) for details.

[Logo / icon](http://www.iconninja.com/earth-search-internet-icon-44388) sourced from iconninja.com ([Archived page](http://riii.me/rftqo))

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