99 lines
3.2 KiB
Go
Vendored
99 lines
3.2 KiB
Go
Vendored
// Copyright (c) 2017 Couchbase, Inc.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
package geo
|
|
|
|
import (
|
|
"fmt"
|
|
"math"
|
|
"strconv"
|
|
"strings"
|
|
)
|
|
|
|
type distanceUnit struct {
|
|
conv float64
|
|
suffixes []string
|
|
}
|
|
|
|
var inch = distanceUnit{0.0254, []string{"in", "inch"}}
|
|
var yard = distanceUnit{0.9144, []string{"yd", "yards"}}
|
|
var feet = distanceUnit{0.3048, []string{"ft", "feet"}}
|
|
var kilom = distanceUnit{1000, []string{"km", "kilometers"}}
|
|
var nauticalm = distanceUnit{1852.0, []string{"nm", "nauticalmiles"}}
|
|
var millim = distanceUnit{0.001, []string{"mm", "millimeters"}}
|
|
var centim = distanceUnit{0.01, []string{"cm", "centimeters"}}
|
|
var miles = distanceUnit{1609.344, []string{"mi", "miles"}}
|
|
var meters = distanceUnit{1, []string{"m", "meters"}}
|
|
|
|
var distanceUnits = []*distanceUnit{
|
|
&inch, &yard, &feet, &kilom, &nauticalm, &millim, ¢im, &miles, &meters,
|
|
}
|
|
|
|
// ParseDistance attempts to parse a distance string and return distance in
|
|
// meters. Example formats supported:
|
|
// "5in" "5inch" "7yd" "7yards" "9ft" "9feet" "11km" "11kilometers"
|
|
// "3nm" "3nauticalmiles" "13mm" "13millimeters" "15cm" "15centimeters"
|
|
// "17mi" "17miles" "19m" "19meters"
|
|
// If the unit cannot be determined, the entire string is parsed and the
|
|
// unit of meters is assumed.
|
|
// If the number portion cannot be parsed, 0 and the parse error are returned.
|
|
func ParseDistance(d string) (float64, error) {
|
|
for _, unit := range distanceUnits {
|
|
for _, unitSuffix := range unit.suffixes {
|
|
if strings.HasSuffix(d, unitSuffix) {
|
|
parsedNum, err := strconv.ParseFloat(d[0:len(d)-len(unitSuffix)], 64)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
return parsedNum * unit.conv, nil
|
|
}
|
|
}
|
|
}
|
|
// no unit matched, try assuming meters?
|
|
parsedNum, err := strconv.ParseFloat(d, 64)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
return parsedNum, nil
|
|
}
|
|
|
|
// ParseDistanceUnit attempts to parse a distance unit and return the
|
|
// multiplier for converting this to meters. If the unit cannot be parsed
|
|
// then 0 and the error message is returned.
|
|
func ParseDistanceUnit(u string) (float64, error) {
|
|
for _, unit := range distanceUnits {
|
|
for _, unitSuffix := range unit.suffixes {
|
|
if u == unitSuffix {
|
|
return unit.conv, nil
|
|
}
|
|
}
|
|
}
|
|
return 0, fmt.Errorf("unknown distance unit: %s", u)
|
|
}
|
|
|
|
// Haversin computes the distance between two points.
|
|
// This implemenation uses the sloppy math implemenations which trade off
|
|
// accuracy for performance. The distance returned is in kilometers.
|
|
func Haversin(lon1, lat1, lon2, lat2 float64) float64 {
|
|
x1 := lat1 * degreesToRadian
|
|
x2 := lat2 * degreesToRadian
|
|
h1 := 1 - cos(x1-x2)
|
|
h2 := 1 - cos((lon1-lon2)*degreesToRadian)
|
|
h := (h1 + cos(x1)*cos(x2)*h2) / 2
|
|
avgLat := (x1 + x2) / 2
|
|
diameter := earthDiameter(avgLat)
|
|
|
|
return diameter * asin(math.Min(1, math.Sqrt(h)))
|
|
}
|