x1、y1 是纬度、经度

Dim x1 As Double = 37.856862
Dim y1 As Double = 112.525760
Dim x2 As Double = 37.857587
Dim y2 As Double = 112.525683

Dim a As Double = p1X - p2X
Dim b As Double = p1Y - p2Y
Dim s As Double = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a/2),2) + Math.Cos(p1X)*Math.Cos(p2X)*Math.Pow(Math.Sin(b/2),2))) * rad
output.show(s)

 没有坐标、没有线路怎么可能计算啊

mark 获取坐标，两点线路

Dim 起点 As String = "天津市西青区西青道三星路1号"
Dim 终点 As String = "青岛市敦化路22号"

Dim rqst As System.Net.HttpWebRequest = System.Net.HttpWebRequest.Create("http://api.map.baidu.com/geocoder/v2/?address=" & 起点 & "&output=json&ak=hAaa2NLELKdAIfMhMjnuEgi1")
Dim rsps As System.Net.HttpWebResponse = rqst.GetResponse
Dim stm As System.IO.Stream = rsps.GetResponseStream()
Dim reader As New System.IO.StreamReader(stm)
Dim json As String = reader.ReadToEnd
\'msgbox(json)
Dim ScriptControl As Object, data  As Object, JscriptCode As String
JscriptCode = "function toObject(json) {eval(""var o=""+json);return o;}"
ScriptControl = CreateObject("MSScriptControl.ScriptControl")
With ScriptControl
    .Language = "Javascript"
    .Timeout = -1
    .AddCode(JscriptCode)
    data = .Run("toObject", json)
End With

Dim lng1 = data.result.location.lng
Dim lat1 = data.result.location.lat

rqst  = System.Net.HttpWebRequest.Create("http://api.map.baidu.com/geocoder/v2/?address=" & 终点 & "&output=json&ak=hAaa2NLELKdAIfMhMjnuEgi1")
rsps = rqst.GetResponse
stm = rsps.GetResponseStream()
reader = New System.IO.StreamReader(stm)
json = reader.ReadToEnd
\'msgbox(json)

JscriptCode = "function toObject(json) {eval(""var o=""+json);return o;}"
ScriptControl = CreateObject("MSScriptControl.ScriptControl")
With ScriptControl
    .Language = "Javascript"
    .Timeout = -1
    .AddCode(JscriptCode)
    data = .Run("toObject", json)
End With

Dim lng2 = data.result.location.lng
Dim lat2 = data.result.location.lat

Dim proc As new Process
proc.file = "http://api.map.baidu.com/direction?origin=latlng:" & lat1 & "," & lng1 & "|name:" & 起点 & "&destination=latlng:" & lat2 & "," & lng2 & "|name:" & 终点 & "&mode=driving&region=西安&output=html&src=yourCompanyName|yourAppName"
\'output.show(proc.file)
proc.start

简单一点就这样

Dim 起点 As String = "天津市西青区西青道三星路1号"
Dim 终点 As String = "青岛市敦化路22号"
Dim proc As new Process
proc.file = "http://api.map.baidu.com/direction?origin=" & 起点 & "&destination=" & 终点 & "&mode=driving&region=西安&output=html&src=yourCompanyName|yourAppName"
output.show(proc.file)
proc.start