這個程式是根據網上找到的VC程式碼改寫而成的Delphi庫單元，經驗算，比較準確，支援西安80及北京54。

程式碼及使用方法如下:

unit Translate; 
{ 
經緯度座標與高斯-克呂格投影座標的互算。 
時間：2009-05-11 
部落格：http://wallimn.iteye.com 
轉載請保留此資訊 
} 
interface 

uses Math; 
type 
TTranslate = class(TObject) 
protected 
a,f,e2,e12:double; 
A1,A2,A3,A4:double; 
private 
L0:double; // 中央子午線經度 
public 
procedure BL2xy(B,L :double; var x,y :double); 
procedure xy2BL(x,y :double; var B,L :double); 
procedure SetL0(dL0:double); 
end; 

TTranslate_Krasovsky = class(TTranslate) 
public 
    constructor Create; 
end; 

TTranslate_IUGG1975=class(TTranslate) 
public 
    constructor Create; 
end; 

function Dms2Rad( Dms:double) : double ; 
function Rad2Dms( Rad:double)  : double  ; 

implementation 
{ 
將度、分、秒形式轉化成弧度 
} 
function Dms2Rad( Dms:double) : double ; 
var 
  Degree,Miniute,Second:Double; 
  Rad:Double; 
  Sign:Integer; 
begin 
if(Dms >= 0) then 
Sign := 1 
else 
Sign := -1; 
Dms := abs(Dms); 
Degree := floor(Dms); 
Miniute := floor(Dms * 100) mod 100; 
Second := floor(Dms * 10000) mod 100; 
Rad := Sign * (Degree + Miniute / 60.0 + Second / 3600.0) * PI / 180.0; 
result:= Rad; 
end; 
{ 
將弧度轉換成度、分、秒錶示形式； 
轉換的結果是度， 
} 
function Rad2Dms( Rad:double)  : double  ; 
var 
  Degree, Miniute, Second:double; 
  Sign:integer; 
begin 
if(Rad >= 0)     then 
Sign := 1 
else 
Sign := -1; 
Rad := abs(Rad * 180.0 / PI); 
Degree := floor(Rad); 
Miniute := floor(Rad * 60) mod 60; 
Second := floor(Rad * 3600) mod 60; 
Result := Sign * (Degree + Miniute / 100.0 + Second / 10000.0); 
  //Result:=Rad * 180/PI; 
end; 
{ TTranslate } 
{ 
B,L　為以度為單位的緯度及經度 
x,y　為轉換結果，即投影座標，其中y不帶帶號 
時間：2009-05-11 
部落格：http://wallimn.iteye.com 
} 
procedure TTranslate.BL2xy(B, L: double; var x, y: double); 
var 
  XX, N, t, t2, m, m2, ng2:double; 
  sinB, cosB:double; 
begin 
  B:= B*PI/180.0; 
  L:= L*PI/180.0; 
XX := A1 * B * 180.0 / PI + A2 * sin(2 * B) + A3 * sin(4 * B) + A4 * sin(6 * B); 
sinB := sin(B); 
cosB := cos(B); 
t := tan(B); 
t2 := t * t; 
N := a / sqrt(1 - e2 * sinB * sinB); 
m := cosB * (L - L0); 
m2 := m * m; 
ng2 := cosB * cosB * e2 / (1 - e2); 
//x,y的計算公式見孔祥元等主編武漢大學出版社2002年出版的《控制測量學》 
x := XX + N * t * ((0.5 + ((5 - t2 + 9 * ng2 + 4 * ng2 * ng2) / 24.0 + (61 - 
58 * t2 + t2 * t2) * m2 / 720.0) * m2) * m2); 
y := N * m * ( 1 + m2 * ( (1 - t2 + ng2) / 6.0 + m2 * ( 5 - 18 * t2 + t2 * t2 
+ 14 * ng2 - 58 * ng2 * t2 ) / 120.0)); 
y := y + 500000; 
end; 

{ 
設定中央子午線的經度，以度為單位 
} 
procedure TTranslate.SetL0(dL0: double); 
begin 
  //L0:= Dms2Rad(dL0); 
  L0:=dL0*PI/180.0; 
end; 
{ 
x,y　投影座標，其中y不帶帶號 
B,L　為轉換結果，以度為單位的緯度及經度 
時間：2009-05-11 
部落格：http://wallimn.iteye.com 
} 

procedure TTranslate.xy2BL(x, y: double; var B, L: double); 
var 
  sinB, cosB, t, t2, N ,ng2, V, yN:double; 
  preB0, B0:double; 
  eta:double; 
begin 
y := y- 500000; 
B0 := x / A1; 
repeat 
begin 
preB0 := B0; 
B0 := B0 * PI / 180.0; 
B0 := (x - (A2 * sin(2 * B0) + A3 * sin(4 * B0) + A4 * sin(6 * B0))) / A1; 
eta := abs(B0 - preB0); 
end 
  until(eta <= 0.000000001); 
B0 := B0 * PI / 180.0; 
B := Rad2Dms(B0); 
sinB := sin(B0); 
cosB := cos(B0); 
t := tan(B0); 
t2 := t * t; 
N := a / sqrt(1 - e2 * sinB * sinB); 
ng2 := cosB * cosB * e2 / (1 - e2); 
V := sqrt(1 + ng2); 
yN := y / N; 
B := B0 - (yN * yN - (5 + 3 * t2 + ng2 - 9 * ng2 * t2) * yN * yN * yN * yN / 
12.0 + (61 + 90 * t2 + 45 * t2 * t2) * yN * yN * yN * yN * yN * yN / 360.0) 
* V * V * t / 2; 
L := L0 + (yN - (1 + 2 * t2 + ng2) * yN * yN * yN / 6.0 + (5 + 28 * t2 + 24 
* t2 * t2 + 6 * ng2 + 8 * ng2 * t2) * yN * yN * yN * yN * yN / 120.0) / cosB; 

  //B:=Rad2Dms(B); 
  //L:=Rad2Dms(L); 
  B:=B*180.0/PI; 
  L:=L*180.0/PI; 
end; 

{ TTranslate_Krasovsky } 

constructor TTranslate_Krasovsky.Create; 
begin 
a := 6378245; 
f := 298.3; 
e2 := 1 - ((f - 1) / f) * ((f - 1) / f); 
e12 := (f / (f - 1)) * (f / (f - 1)) - 1; 
A1 := 111134.8611; 
A2 := -16036.4803; 
A3 := 16.8281; 
A4 := -0.0220; 
end; 

{ TTranslate_IUGG1975 } 

constructor TTranslate_IUGG1975.Create; 
begin 
a := 6378140; 
f := 298.257; 
e2 := 1 - ((f - 1) / f) * ((f - 1) / f); 
e12 := (f / (f - 1)) * (f / (f - 1)) - 1; 
A1 := 111133.0047;  //這幾個A是什麼意思？ 
A2 := -16038.5282; 
A3 := 16.8326; 
A4 := -0.0220; 
end; 

end. 
 

引用此庫單元，具體使用方法如下：

 
procedure TFrmMain.Button1Click(Sender: TObject); 
var 
t:TTranslate; 
L,B:Double; 
begin 
t :=TTranslate_IUGG1975.create; 
t.SetL0(111); 
t.xy2BL(strToFloat(edtX.text),strToFloat(edtY.text),L,B); 
showmessage('L='+FloatToStr(L)+' B='+FloatToStr(B)); 
//執行結果：L=20,B=109.15 
end;