53 lines
1.6 KiB
Go
53 lines
1.6 KiB
Go
// Copyright 2017 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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package pipoint
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import (
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"math"
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)
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const (
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m1 = 111132.92 // latitude calculation term 1
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m2 = -559.82 // latitude calculation term 2
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m3 = 1.175 // latitude calculation term 3
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m4 = -0.0023 // latitude calculation term 4
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p1 = 111412.84 // longitude calculation term 1
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p2 = -93.5 // longitude calculation term 2
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p3 = 0.118 // longitude calculation term 3
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)
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// LatLength returns the length of a line of latitude at the given
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// latitude. Input is in rad, output in m.
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func LatLength(lat float64) float64 {
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return m1 + m2*math.Cos(2*lat) + m3*math.Cos(4*lat)
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}
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// LonLength returns the length of a line of longitude at the given
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// latitude. Input is in rad, output in m.
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func LonLength(lat float64) float64 {
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return p1*math.Cos(lat) + p2*math.Cos(3*lat) + p3*math.Cos(5*lat)
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}
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// AsRad converts degrees to radians.
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func AsRad(deg float64) float64 {
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return deg * (math.Pi / 180)
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}
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// AsDeg converts radians to degrees.
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func AsDeg(rad float64) float64 {
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return rad * (180 / math.Pi)
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}
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