geo.go

geo.go - Overview

This file provides geographical functions, including distance calculations and GeoHash encoding/decoding.

Detailed Documentation

const earthRadius float64

const earthRadius float64 = 6372797.560856

• Purpose: Defines the Earth's radius in meters.

const bitPrecision int

const bitPrecision = 52

• Purpose: Defines the bit precision for GeoHash.

const bitPrecisionString int

const bitPrecisionString = 10

• Purpose: Defines the bit precision for GeoHash strings.

func DegToRad(deg float64) float64

func DegToRad(deg float64) float64 {
	return math.Pi * deg / 180.0
}

• Purpose: Converts degrees to radians.
  • Parameters:
    • deg: The angle in degrees.
  • Returns: The angle in radians.

func RadToDeg(rad float64) float64

func RadToDeg(rad float64) float64 {
	return 180.0 * rad / math.Pi
}

• Purpose: Converts radians to degrees.
  • Parameters:
    • rad: The angle in radians.
  • Returns: The angle in degrees.

func GetDistance(lon1 float64, lat1 float64, lon2 float64, lat2 float64) float64

func GetDistance(
	lon1,
	lat1,
	lon2,
	lat2 float64,
) float64 {
	lon1r := DegToRad(lon1)
	lon2r := DegToRad(lon2)
	v := math.Sin((lon2r - lon1r) / 2)
	// if v == 0 we can avoid doing expensive math when lons are practically the same
	if v == 0.0 {
		return GetLatDistance(lat1, lat2)
	}

	lat1r := DegToRad(lat1)
	lat2r := DegToRad(lat2)
	u := math.Sin((lat2r - lat1r) / 2)

	a := u*u + math.Cos(lat1r)*math.Cos(lat2r)*v*v

	return 2.0 * earthRadius * math.Asin(math.Sqrt(a))
}

• Purpose: Calculates the distance between two points on Earth using the Haversine formula.
  • Parameters:
    • lon1: Longitude of the first point in degrees.
    • lat1: Latitude of the first point in degrees.
    • lon2: Longitude of the second point in degrees.
    • lat2: Latitude of the second point in degrees.
  • Returns: The distance between the two points in meters.

func GetLatDistance(lat1 float64, lat2 float64) float64

func GetLatDistance(lat1, lat2 float64) float64 {
	return earthRadius * math.Abs(DegToRad(lat2)-DegToRad(lat1))
}

• Purpose: Calculates the distance between two points on the same longitude.
  • Parameters:
    • lat1: Latitude of the first point in degrees.
    • lat2: Latitude of the second point in degrees.
  • Returns: The distance between the two points in meters.

func EncodeInt(lat float64, lon float64) float64

func EncodeInt(lat, lon float64) float64 {
	h := geohash.EncodeIntWithPrecision(lat, lon, bitPrecision)

	return float64(h)
}

• Purpose: Encodes latitude and longitude into a GeoHash integer.
  • Parameters:
    • lat: Latitude in degrees.
    • lon: Longitude in degrees.
  • Returns: The GeoHash as a float64.

func DecodeInt(hash float64) (lat float64, lon float64)

func DecodeInt(hash float64) (lat, lon float64) {
	lat, lon = geohash.DecodeIntWithPrecision(uint64(hash), bitPrecision)

	return lat, lon
}

• Purpose: Decodes a GeoHash integer into latitude and longitude.
  • Parameters:
    • hash: The GeoHash as a float64.
  • Returns:
    • lat: Latitude in degrees.
    • lon: Longitude in degrees.

func EncodeString(lat float64, lon float64) string

func EncodeString(lat, lon float64) string {
	return geohash.EncodeWithPrecision(lat, lon, bitPrecisionString)
}

• Purpose: Encodes latitude and longitude into a GeoHash string.
  • Parameters:
    • lat: Latitude in degrees.
    • lon: Longitude in degrees.
  • Returns: The GeoHash string.

func ConvertDistance(distance float64, unit string) (converted float64, err []byte)

func ConvertDistance(
	distance float64,
	unit string,
) (converted float64, err []byte) {
	switch unit {
	case "m":
		return distance, nil
	case "km":
		return distance / 1000, nil
	case "mi":
		return distance / 1609.34, nil
	case "ft":
		return distance / 0.3048, nil
	default:
		return 0, errors.NewErrWithMessage("ERR unsupported unit provided. please use m, km, ft, mi")
	}
}

• Purpose: Converts a distance from meters to the specified unit.
  • Parameters:
    • distance: The distance in meters.
    • unit: The unit to convert to ("m", "km", "mi", "ft").
  • Returns:
    • converted: The converted distance.
    • err: An error message if the unit is unsupported.

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