// Reverse geocode
func (g *GeoBed) ReverseGeocode(lat float64, lng float64) GeobedCity {
c := GeobedCity{}
gh := geohash.Encode(lat, lng)
// This is produced with empty lat/lng values - don't look for anything.
if gh == "7zzzzzzzzzzz" {
return c
}
// Note: All geohashes are going to be 12 characters long. Even if the precision on the lat/lng isn't great. The geohash package will center things.
// Obviously lat/lng like 37, -122 is a guess. That's no where near the resolution of a city. Though we're going to allow guesses.
mostMatched := 0
matched := 0
for k, v := range g.c {
// check first two characters to reduce the number of loops
if v.Geohash[0] == gh[0] && v.Geohash[1] == gh[1] {
matched = 2
for i := 2; i <= len(gh); i++ {
//log.Println(gh[0:i])
if v.Geohash[0:i] == gh[0:i] {
matched++
}
}
// tie breakers go to city with larger population (NOTE: There's still a chance that the next pass will uncover a better match)
if matched == mostMatched && g.c[k].Population > c.Population {
c = g.c[k]
// log.Println("MATCHES")
// log.Println(matched)
// log.Println("CITY")
// log.Println(c.City)
// log.Println("POPULATION")
// log.Println(c.Population)
}
if matched > mostMatched {
c = g.c[k]
mostMatched = matched
}
}
}
return c
}
// Unzips the data sets and loads the data.
func (g *GeoBed) loadDataSets() {
locationDedupeIdx = make(map[string]bool)
for _, f := range dataSetFiles {
// This one is zipped
if f["id"] == "geonamesCities1000" {
rz, err := zip.OpenReader(f["path"])
if err != nil {
log.Fatal(err)
}
defer rz.Close()
for _, uF := range rz.File {
fi, err := uF.Open()
if err != nil {
log.Fatal(err)
}
defer fi.Close()
// Geonames uses a tab delineated format and it's not even consistent. No CSV reader that I've found for Go can understand this.
// I'm not expecting any reader to either because it's an invalid CSV to be frank. However, we can still split up each row by \t
scanner := bufio.NewScanner(fi)
scanner.Split(bufio.ScanLines)
i := 1
for scanner.Scan() {
i++
// So regexp, sadly, must be used (well, unless I wanted parse each string byte by byte, pushing each into a buffer to append to a slice until a tab is reached, etc.).
// But I'd have to also then put in a condition if the next byte was a \t rune, then append an empty string, etc. This just, for now, seems nicer (easier).
// This is only an import/update, so it shouldn't be an issue for performance. If it is, then I'll look into other solutions.
fields := regexp.MustCompile("\t").Split(scanner.Text(), 19)
// NOTE: Now using a combined GeobedCity struct since not all data sets have the same fields.
// Plus, the entire point was to geocode forward and reverse. Bonus information like elevation and such is just superfluous.
// Leaving it here because it may be configurable... If options are passed to NewGeobed() then maybe Geobed can simply be a Geonames search.
// Don't even load in MaxMind data...And if that's the case, maybe that bonus information is desired.
if len(fields) == 19 {
//id, _ := strconv.Atoi(fields[0])
lat, _ := strconv.ParseFloat(fields[4], 64)
lng, _ := strconv.ParseFloat(fields[5], 64)
pop, _ := strconv.Atoi(fields[14])
//elv, _ := strconv.Atoi(fields[15])
//dem, _ := strconv.Atoi(fields[16])
gh := geohash.Encode(lat, lng)
// This is produced with empty lat/lng values - don't store it.
if gh == "7zzzzzzzzzzz" {
gh = ""
}
var c GeobedCity
c.City = strings.Trim(string(fields[1]), " ")
c.CityAlt = string(fields[3])
c.Country = string(fields[8])
c.Region = string(fields[10])
c.Latitude = lat
c.Longitude = lng
c.Population = int32(pop)
c.Geohash = gh
// Don't include entries without a city name. If we want to geocode the centers of countries and states, then we can do that faster through other means.
if len(c.City) > 0 {
g.c = append(g.c, c)
}
}
}
}
}
// ...And this one is Gzipped (and this one may have worked with the CSV package, but parse it the same way as the others line by line)
if f["id"] == "maxmindWorldCities" {
// It also has a lot of dupes
maxMindCityDedupeIdx = make(map[string][]string)
fi, err := os.Open(f["path"])
if err != nil {
log.Println(err)
}
defer fi.Close()
fz, err := gzip.NewReader(fi)
if err != nil {
log.Println(err)
}
defer fz.Close()
scanner := bufio.NewScanner(fz)
scanner.Split(bufio.ScanLines)
i := 1
for scanner.Scan() {
i++
t := scanner.Text()
fields := strings.Split(t, ",")
if len(fields) == 7 {
var b bytes.Buffer
b.WriteString(fields[0]) // country
b.WriteString(fields[3]) // region
b.WriteString(fields[1]) // city
idx := b.String()
b.Reset()
maxMindCityDedupeIdx[idx] = fields
}
}
// Loop the map of fields after dupes have been removed (about 1/5th less... 2.6m vs 3.1m inreases lookup performance).
for _, fields := range maxMindCityDedupeIdx {
if fields[0] != "" && fields[0] != "0" {
if fields[2] != "AccentCity" {
pop, _ := strconv.Atoi(fields[4])
lat, _ := strconv.ParseFloat(fields[5], 64)
lng, _ := strconv.ParseFloat(fields[6], 64)
// MaxMind's data set is a bit dirty. I've seen city names surrounded by parenthesis in a few places.
cn := strings.Trim(string(fields[2]), " ")
cn = strings.Trim(cn, "( )")
// Don't take any city names with erroneous punctuation either.
if strings.Contains(cn, "!") || strings.Contains(cn, "@") {
continue
}
gh := geohash.Encode(lat, lng)
// This is produced with empty lat/lng values - don't store it.
if gh == "7zzzzzzzzzzz" {
gh = ""
}
// If the geohash was seen before...
_, ok := locationDedupeIdx[gh]
if !ok {
locationDedupeIdx[gh] = true
var c GeobedCity
c.City = cn
c.Country = toUpper(string(fields[0]))
c.Region = string(fields[3])
c.Latitude = lat
c.Longitude = lng
c.Population = int32(pop)
c.Geohash = gh
// Don't include entries without a city name. If we want to geocode the centers of countries and states, then we can do that faster through other means.
if len(c.City) > 0 && len(c.Country) > 0 {
g.c = append(g.c, c)
}
}
}
}
}
// Clear out the temrporary index (set to nil, it does get re-created) so that Go can garbage collect it at some point whenever it feels the need.
maxMindCityDedupeIdx = nil
locationDedupeIdx = nil
}
// ...And this one is just plain text
if f["id"] == "geonamesCountryInfo" {
fi, err := os.Open(f["path"])
if err != nil {
log.Fatal(err)
}
defer fi.Close()
scanner := bufio.NewScanner(fi)
scanner.Split(bufio.ScanLines)
i := 1
for scanner.Scan() {
t := scanner.Text()
// There are a bunch of lines in this file that are comments, they start with #
if string(t[0]) != "#" {
i++
fields := regexp.MustCompile("\t").Split(t, 19)
if len(fields) == 19 {
if fields[0] != "" && fields[0] != "0" {
isoNumeric, _ := strconv.Atoi(fields[2])
area, _ := strconv.Atoi(fields[6])
pop, _ := strconv.Atoi(fields[7])
gid, _ := strconv.Atoi(fields[16])
var ci CountryInfo
ci.ISO = string(fields[0])
ci.ISO3 = string(fields[1])
ci.ISONumeric = int16(isoNumeric)
ci.Fips = string(fields[3])
ci.Country = string(fields[4])
ci.Capital = string(fields[5])
ci.Area = int32(area)
ci.Population = int32(pop)
ci.Continent = string(fields[8])
ci.Tld = string(fields[9])
ci.CurrencyCode = string(fields[10])
ci.CurrencyName = string(fields[11])
ci.Phone = string(fields[12])
ci.PostalCodeFormat = string(fields[13])
ci.PostalCodeRegex = string(fields[14])
ci.Languages = string(fields[15])
ci.GeonameId = int32(gid)
ci.Neighbours = string(fields[17])
ci.EquivalentFipsCode = string(fields[18])
g.co = append(g.co, ci)
}
}
}
}
}
}
// Sort []GeobedCity by city names to help with binary search (the City field is the most searched upon field and the matching names can be easily filtered down from there).
sort.Sort(g.c)
//debug
//log.Println("TOTAL RECORDS:")
//log.Println(len(g.c))
// Index the locations of city names in the g.c []GeoCity slice. This way when searching the range can be limited so it will be faster.
cityNameIdx = make(map[string]int)
for k, v := range g.c {
// Get the index key for the first character of the city name.
ik := toLower(string(v.City[0]))
if val, ok := cityNameIdx[ik]; ok {
// If this key number is greater than what was previously recorded, then set it as the new indexed key.
if val < k {
cityNameIdx[ik] = k
}
} else {
// If the index key has not yet been set for this value, then set it.
cityNameIdx[ik] = k
}
// Get the index key for the first two characters of the city name.
// if len(v.CityLower) >= 2 {
// ik2 := v.CityLower[0:2]
// if val, ok := cityNameIdx[ik2]; ok {
// // If this key number is greater than what was previously recorded, then set it as the new indexed key.
// if val < k {
// cityNameIdx[ik2] = k
// }
// } else {
// // If the index key has not yet been set for this value, then set it.
// cityNameIdx[ik2] = k
// }
// }
}
}