How to extract Geographic data from open street map or Google maps

Question

i need to retrieve all the city names from a specific country using openstreet map or google maps. is there any API available?

or is there any other way of getting this world geographic data?

Answer 1

You should definitely checkout GeoNames. They have the entire world in a standardized database. You can download it or use their API.

I download the US database and use a connector I created in C# to insert States, Cities, Towns, and Zip Codes in my database.

    public static class GeoNamesConnector
{
    #region GeoName Constants
    private static readonly string GeoNamesPath = HttpContext.Current.Server.MapPath("~/App_Data/GeoNames/US.txt");
    const int GeoNameIdColumn = 0;
    const int NameColumn = 1;
    const int LatitudeColumn = 4;
    const int LongitudeColumn = 5;
    const int FeatureCodeColumn = 7;
    const int CountryCodeColumn = 8;
    const int Admin1CodeColumn = 10;
    const int Admin2CodeColumn = 11;
    #endregion

    #region AlternateName Constants
    private static readonly string AlternateNamesPath = HttpContext.Current.Server.MapPath("~/App_Data/GeoNames/alternateNames.txt");
    const int AlternateNameIdColumn = 0;
    const int AltNameGeoNameIdColumn = 1;
    const int IsoLanguageColumn = 2;
    const int AlternateNameColumn = 3;
    #endregion

    public static void AddAllEntities(GeoNamesEntities entities)
    {
        //Remember to turn off Intellitrace
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.Start();
        var geoNamesSortedList = AddGeoNames(entities);
        Trace.WriteLine(String.Format("Added GeoNames: {0}", stopwatch.Elapsed));
        stopwatch.Restart();

        SetupGeoNameChildRelationships(geoNamesSortedList, entities);
        Trace.WriteLine(String.Format("Setup GeoName parent/child relationships: {0}", stopwatch.Elapsed));
        stopwatch.Restart();

        AddPostalCodeAlternateNames(geoNamesSortedList, entities);
        Trace.WriteLine(String.Format("Added postal codes and relationships with parent GeoNames: {0}", stopwatch.Elapsed));
    }

    private static SortedList<int, GeoName> AddGeoNames(GeoNamesEntities entities)
    {
        var lineReader = File.ReadLines(GeoNamesPath);
        var geoNames = from line in lineReader.AsParallel()
                       let fields = line.Split(new char[] { '\t' })
                       let fieldCount = fields.Length
                       where fieldCount >= 9
                       let featureCode = fields[FeatureCodeColumn]
                       where featureCode == "ADM1" || featureCode == "ADM2" || featureCode == "PPL"
                       let name = fields[NameColumn]
                       let id = string.IsNullOrEmpty(fields[GeoNameIdColumn]) ? 0 : int.Parse(fields[GeoNameIdColumn])
                       orderby id
                       select new GeoName
                       {
                           Id = Guid.NewGuid(),
                           GeoNameId = id,
                           Name = fields[NameColumn],
                           Latitude = string.IsNullOrEmpty(fields[LatitudeColumn]) ? 0 : Convert.ToDecimal(fields[LatitudeColumn]),
                           Longitude = string.IsNullOrEmpty(fields[LongitudeColumn]) ? 0 : Convert.ToDecimal(fields[LongitudeColumn]),
                           FeatureCode = featureCode,
                           CountryCode = fields[CountryCodeColumn],
                           Admin1Code = fieldCount < 11 ? "" : fields[Admin1CodeColumn],
                           Admin2Code = fieldCount < 12 ? "" : fields[Admin2CodeColumn]
                       };
        var sortedList = new SortedList<int, GeoName>();
        int i = 1;
        foreach (var geoname in geoNames)
        {
            sortedList.Add(geoname.GeoNameId, geoname);
            entities.GeographicAreas.AddObject(geoname);
            if (i++ % 20000 == 0)
                entities.SaveChanges();
        }
        entities.SaveChanges();
        return sortedList;
    }

    private static void SetupGeoNameChildRelationships(SortedList<int, GeoName> geoNamesSortedList, GeoNamesEntities entities)
    {
        foreach (var geoName in geoNamesSortedList.Where(g => g.Value.FeatureCode == "ADM2" || g.Value.FeatureCode == "ADM1"))
        {
            //Setup parent child relationship
            IEnumerable<KeyValuePair<int, GeoName>> children = null;
            switch (geoName.Value.FeatureCode)
            {
                case "ADM1":
                    children =
                        geoNamesSortedList.Where(
                            g =>
                            g.Value.FeatureCode == "ADM2" &&
                            g.Value.Admin1Code == geoName.Value.Admin1Code);
                    break;
                case "ADM2":
                    children =
                        geoNamesSortedList.Where(
                            g =>
                            g.Value.FeatureCode == "PPL" &&
                            g.Value.Admin1Code == geoName.Value.Admin1Code &&
                            g.Value.Admin2Code == geoName.Value.Admin2Code);
                    break;
            }
            if (children != null)
            {
                foreach (var child in children)
                    geoName.Value.Children.Add(child.Value);
            }
            entities.SaveChanges();
        }
    }

    private static void AddPostalCodeAlternateNames(SortedList<int, GeoName> geoNamesSortedList, GeoNamesEntities entities)
    {
        var lineReader = File.ReadLines(AlternateNamesPath);
        var alternativeNames = from line in lineReader.AsParallel()
                               let fields = line.Split(new char[] { '\t' })
                               let fieldCount = fields.Length
                               where fieldCount >= 4 && fields[IsoLanguageColumn] == "post"
                               let geoNameId = int.Parse(fields[AltNameGeoNameIdColumn])
                               orderby geoNameId
                               select new AlternateName
                               {
                                   Id = Guid.NewGuid(),
                                   AlternateNameId = int.Parse(fields[AlternateNameIdColumn]),
                                   ParentGeoNameId = geoNameId,
                                   Name = fields[AlternateNameColumn],
                                   IsoLanguage = fields[IsoLanguageColumn]
                               };
        //Iterate through to convert from lazy (AsParallel) so it is ready for use
        foreach (var alternateName in alternativeNames)
        {
            int key = alternateName.ParentGeoNameId;
            if (geoNamesSortedList.ContainsKey(key))
            {
                entities.GeographicAreas.AddObject(alternateName);
                alternateName.Parent = geoNamesSortedList[key];
            }
        }
        entities.SaveChanges();
    }

}

There is also Open Street Maps that you can download or use their API.

I do not suggest Yahoo's new API they are cutting products left and right and you never know how long it will be around. Also you cannot download a whole dump currently.