GridLocW - a Lat/Long to Maidenhead converter for Windows - with optional GPS support

{ GridLocW : Grid Locator (for) Windows }

{ Name derived from the various versions of Gridloc around on the web - most of which are DOS or BASIC (eg GWBASIC) releases }

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A side issue from operating in the 2009 John Moyle Field Day was the fact that some operators - particularly home stations - did not know their (maidenhead) grid squares. To make it easier for any future field days, I wrote GridLocW - Grid Locator (for) Windows - in the pascal-based environment of "Delphi". That way, provided they can give me a latitude and longtitude, I can calculate it for them via software loaded on the logging PC - and then tell them as well - as using it in the log itself. Of course, it has a side benefit for any field day operators in that it has internal GPS support that can tell them exactly what grid square they are in - all they need to do is connect a suitable GPS to the PC via a serial port -and run GridLocW !

Best of all, it''s free !

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While doing a bit of research on Latitude/Longtitude to Maidenhead converters, I discovered that the likes of the ARRL only have links to DOS-based converters on their web site and that led me to extract some code from a Delphi-based application that I have been using for some time. The result is a program that will will run on any 32 bit version of Windows - ie Win 2000 and up, does decimal or degrees/minutes/seconds cross-conversions as well as the Maidenhead grid squares.

To make it easier to use in some situations, I have written in some simple GPS support to determine latitude and longtitude details. Most GPS devices that output data to a serial port ( direct or via a serial/USB adapter) should work with this software. You will still need to press the "Convert" button to obtain your grid square details.. Hey, YOU have to do something.

The "Raw" tickbox allows part of the GPS data to be displayed so that you will find it easier to determine that you are on the correct COM port. Once you know, you will probably never use Raw again.

Please do not copy the file/s from this site and publish them on any other sites otherwise software revisions will not be apparent - and that means bugs will not be fixed in those versions. Always link to the actual files here so that any downloads come only from this site.

• The Clear Dec button clears only the Decimal format boxes and Maidenhead grid
• The Clear D/M/S button clears only the D/M/S format boxes and Maidenhead grid
• The Clear All button clears all of the Lat/Long boxes and Maidenhead grid

• that GPS devices can have different message streams so may not display all of the available selections in the Raw GPS Data box.
• the Time detail in some GPS data has decimals of seconds available while others do not.
• just be sure that you have satellite acquisition BEFORE YOU COMPLAIN THAT THE GPS PART DOESN'T WORK !
• The "Latest Version" button will take you to this web page provided that you have a valid internet connection at the time.

GridLocW.EXE : NO LONGER AVAILABLE FOR DOWNLOAD - SEE GridLocWM.exe below
( right-click and Save Target As.. ) { about 490KB }

OR

GridLocW.ZIP : NO LONGER AVAILABLE FOR DOWNLOAD - SEE GridLocWM.zip below
(right-click and Save Target As.. ) { about 260KB }
[ ZIP contains 1 file ]

THIS version is dated 20/3/2009 and is known to have some "bugs"....
AND WILL NOT BE UPDATED FURTHER - SEE GRIDLOCWM BELOW FOR ALL LATER REVISIONS

There is greater error trapping included in the later releases !

Note - the above images may not show the current release date and all functions

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For those of you who want "more", there is an additional version of GridLocW called GridLocWM which has a world map facility built-in - which works in two ways.

The displayed info from the cursor position is reasonably accurate however as the map is not perfect, there are some small errors noted - particularly towards the RH side. The textual info is correct.

Because the map graphic is included within the application, this version is considerably larger to download.
Note that map operation is inhibited on screen resolutions smaller than 1024 x 768 pixels.

This is what the main program screen looks like....

(Mouse over to see full size)

CHANGELOG :

Note : in Australia, we use DD/MM/YY format so all dates quoted in documentation are this format.

As of the version dated 02/04/2009, there is also an Australian map option which is accessed by selecting the AUS box next to the map button.
Note that by the time places like Tasmania are accessed, the linearity of the map itself is not particularly good and some positioning errors are introduced,
this being a normal situation with Mercator-series maps. Unfortunately I have not located any suitable linear-scaled maps on the web.
( I could have removed Tassie but then some 'Taswegians' would have been upset. )

Minor changes at Version dated 15/5/09 : Added automatical recall of main program position, updated date formats to suit international users, last COM port, last map used etc.. plus a map of the USA & some of the Central Americas. Maps ( World, Aus, USA) are selected from a drop-down box at LHS. Size is now 4.7MB as an EXE, 1MB as a ZIP.

Minor changes at Version dated 16/5/09 : Added mouse pointer distance plus bearing from GPS location - featured only on World map - using Vincenty's formula. Added an extra checkbox on primary screen to allow display of Imperial measurements of GPS height and any distances (Metric is standard). Size is still around 4.7MB as an EXE, 1MB as a ZIP.

Minor changes at Version dated 19/5/09 : Added an entry box for a destination Maidenhead Grid plus a Calculate button to convert back to a Latitude and Longtitude (at the centre of the grid), plus a distance in Km (/ Statute Miles) and bearing in degrees FROM the main Calculated Grid value.

Minor changes at Version dated 20/5/09 : Added mouse pointer distance plus bearing from GPS location to the USA and Australian maps. When right-clicking on a map, a Summary box appears with the Lat/ Long/ Grid / Distance / Bearing values 'frozen'. The Summary box can be moved from over the map (to a clear part of screen) and subsequent left-clicks on alternate map areas will update the 'frozen' data. Added more error trapping for occasional floating point, COM and initial Windows registry startup errors.

World:
Locator JJ00 is at 0 degrees latitude, 0 degrees longtitude and is the default marker placed when there are no Lat and Long values in the decimal degrees boxes.

AUS Map :

USA Map :

Other maps may be added in future releases IF I can find suitable linear map images.

GridLocWM.EXE
( right-click and Save Target As.. ) { about 4.8MB }

OR

GridLocWM.ZIP
(right-click and Save Target As.. ) { about 1000KB }
[ ZIP contains 1 file ]

Current version is dated 19/5/2009

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No installation is necessary for either version, no setup.exe, no additional files. Just run GridLocW.exe / GridLocWM.exe from the folder it is saved/extracted into..

Free to download, free to use, but please - no copies on other websites.

If, perchance, your GPS does not decode correctly then use something like Windows HyperTerminal to capture some of the raw GPS serial output into a text file to email to me.
Please make sure that the device has a good satellite acquisition window by taking the unit to near a door, window or even outside.

Formatting/indentation of the Delphi code has been lost in the functions & procedure listed below, which is normal for web pages which only allow one space between characters & no tabs. Even so, those who need to should be able to copy and paste into a Delphi Unit for inclusion with their own code to create an application.

------------------------------------ Added 30 June 2009 ------------------------------------

For those who are seeking info/code on Vincenty's formula in Delphi :

//* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
//* Vincenty Inverse Solution of Geodesics on the Ellipsoid (c) Chris Veness 2002-2008, edited to suit Delphi 5 by Doug Hunter VK4ADC 2009 */
//* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

//*
// * Calculate geodesic distance (in m) between two points specified by latitude/longitude
// * (in numeric degrees) using Vincenty inverse formula for ellipsoids
// Returns the distance as the function result, the forward azimuth in the var Azim in the calling variable.

// eg yy := distVincenty(strtofloat(form1.edit1.text), strtofloat(form1.edit2.text), strtofloat(form1.edit3.text), strtofloat(form1.edit4.text), zz);
// where edit1 & edit 2 are first Lat & Long (respectively) in decimal format, edit3 and edit 4 are second Lat & Long (respectively) in decimal format, returns distance in metres in yy (real), azimuth in degrees in zz (real), // */

function distVincenty(lat1, lon1, lat2, lon2 : real; var azim : real) : real;

var
a, b, c, f, U1, U2, uSq, sinU1, sinU2, CosU1, CosU2,lambda, lambdap, sinlambda, sinsigma, coslambda, cossigma, sigma, sinalpha, cosSqalpha, cos2sigmam, deltasigma : double;
l, aa, bb, s, rads, a1, a2 : real;
iterlimit : integer;

begin
azim := 0;
rads := pi / 180;
a := 6378137; b := 6356752.3142; f := 1/298.257223563; // WGS-84 ellipsoid
L := (lon2-lon1)* rads;
U1 := arctan((1-f) * tan(lat1 * rads));
U2 := arctan((1-f) * tan(lat2 * rads));
sinU1 := sin(U1);
cosU1 := cos(U1);
sinU2 := sin(U2);
cosU2 := cos(U2);

lambda := L;
lambdaP := 100;
iterLimit := 100;
while (abs(lambda-lambdaP) > 1e-12) and (iterLimit>0) do
begin
sinLambda := sin(lambda);
cosLambda := cos(lambda);
sinSigma := sqrt((cosU2*sinLambda) * (cosU2*sinLambda) +
(cosU1*sinU2-sinU1*cosU2*cosLambda) * (cosU1*sinU2-sinU1*cosU2*cosLambda));
if (sinSigma =0) then
begin // co-incident points
iterlimit := 0;
exit;
end;
cosSigma := sinU1*sinU2 + cosU1*cosU2*cosLambda;
sigma := arctan2(sinSigma, cosSigma);
sinAlpha := cosU1 * cosU2 * sinLambda / sinSigma;
cosSqAlpha := 1 - sinAlpha*sinAlpha;
if (sinU1 <> 0) and (sinU2 <> 0) and (cosSqAlpha <> 0)
then cos2SigmaM := cosSigma - 2*sinU1*sinU2/cosSqAlpha
else cos2SigmaM := cosSigma;
if cos2SigmaM = 0 then
begin
iterlimit := 0;
exit; // equatorial line: cosSqAlpha=0 (§6)
end;
C := f/16*cosSqAlpha*(4+f*(4-3*cosSqAlpha));
lambdaP := lambda;
lambda := L + (1-C) * f * sinAlpha *
(sigma + C*sinSigma*(cos2SigmaM+C*cosSigma*(-1+2*cos2SigmaM*cos2SigmaM)));

dec(iterlimit);
end;

if (iterLimit = 0) then result := 0
else
begin // formula failed to converge

uSq := cosSqAlpha * (a*a - b*b) / (b*b);
AA := 1 + uSq/16384*(4096+uSq*(-768+uSq*(320-175*uSq)));
BB := uSq/1024 * (256+uSq*(-128+uSq*(74-47*uSq)));
deltaSigma := BB*sinSigma*(cos2SigmaM+BB/4*(cosSigma*(-1+2*cos2SigmaM*cos2SigmaM)-
BB/6*cos2SigmaM*(-3+4*sinSigma*sinSigma)*(-3+4*cos2SigmaM*cos2SigmaM)));
s := b*AA*(sigma-deltaSigma);

a1 := arctan2(cosU2*sinlambda, cosU1*sinU2 - sinU1*cosU2*coslambda);
a2 := arctan2(cosU1*sinlambda, -sinU1*cosU2 + cosU1*sinU2*coslambda);

// same lines as above but with different variable names to be declared globally

// fwdAz = arctan2(cosU2*sinLambda, cosU1*sinU2-sinU1*cosU2*cosLambda);
// revAz = arctan2(cosU1*sinLambda, -sinU1*cosU2+cosU1*sinU2*cosLambda);

azim := a1; // Forward azimuth in degrees, only really need this one
result := s; // distance in metres
end;
end;

For those who are seeking info/code on con conversion of Latitude and Longtitude to a Maidenhead Grid locator in Delphi :

// Not the neatest code I have encountered but certainly works.

// Pass it the Lat and long values (eg -27.3 & 153.2 ) and returns the Maidenhead code as the result.
// eg form1.edit9.text := latlong_to_maidenhead(lat,long);

function latlong_to_maidenhead(lat_d,long_d : real): string;
var alphas, nums, codes : string;
g1zz,g2zz,g3zz,g4zz,g5zz,g6zz : string;
ge,te : real;
g1,g2,g3,g4,g5,g6 : integer;

nszz,ewzz, sv : string;
begin
alphas := 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
nums := '0123456789';

{CALCULATE THE GRID LOCATOR}

GE := (Long_D+ 180) / 20;
TE := (Lat_d + 90) / 10;
G1 := trunc(GE);
G2 := trunc(TE);
G1ZZ := alphas[G1+1];
G2ZZ := alphas[G2+1];

GE := (GE - G1) * 10;
TE := (TE - g2) * 10;
G3 := trunc(GE) ;
G4 := trunc(TE);
G3ZZ := nums[G3+1];
G4ZZ := nums[G4+1];

G5 := trunc((GE - G3)*24);
G6 := trunc((TE - G4)*24);
G5ZZ := alphas[G5+1];
G6ZZ := alphas[G6+1];

sv := G1ZZ+G2ZZ+G3ZZ+G4ZZ;
if (trunc(lat_d) = lat_d) and (trunc(long_d) = long_d) then result := sv else
result := sv+lowercase(G5ZZ)+lowercase(G6ZZ);

end;

For those who are seeking info/code on conversion of a Maidenhead Grid locator back to Latitude and Longtitude in Delphi :

// Again, not the neatest code I have encountered but certainly works.

Variables : mh = maidenhead in 4 or 6 charcater format, Lat : lat:6:2, Long : long:6:2

PROCEDURE maidenhead_to_latlong(mh : string; var lat,long : real);

var g1,g2,g3,g4,g5,g6 : integer;
g1s,g2s,g3s,g4s,g5s,g6s : char;
a,b,c,d : integer;
s1,s2,s3,s4 : string;
ge,te,gn,tn : real;

begin
lat := 0;
long := 0;

a := length(mh);
if a < 4 then
begin
lat := 0;
long := 0;
exit;
end;

{ upper case}
for b := 1 to a do mh[b] := upcase(mh[b]);

{ separate chars of maidenhead code }
for b := 1 to a do
begin
case b of
1 : g1s := mh[1];
2 : g2s := mh[2];
3 : g3s := mh[3];
4 : g4s := mh[4];
5 : g5s := mh[5];
6 : g6s := mh[6];
end;
end;

{ allow for last 2 chars to be missing}
if a = 4 then
begin
g5 := 0;
g6 := 0;
g5s := chr(0);
g6s := chr(0);
end;

g1 := ord(g1s) - 65;
g2 := ord(g2s) - 65;
g3 := ord(g3s) - 48;
g4 := ord(g4s) - 48;
g5 := ord(g5s) - 65;
g6 := ord(g6s) - 65;

ge := 20 * g1;
te := 10 * g2;
gn := 0;
tn := 0;
ge := ge + (2 * G3);
te := te + g4;
if a > 4 then
begin
gn := g5 * 5;
if gn > 59 then ge := ge + 1;
if gn > 59 then gn := gn - 60;
tn := 2.5 * g6;
end;

ge := int(ge - 180);
if ge < 0 then gn := 60 - gn;
if ge < 0 then
begin
if g5 = 0 then ge := ge + 1;
end;
gn := int(g5 div 5) * 5;

long:= (ge)+ (gn / 60);

te := int(te - 90);
if te < 0 then gn := 60 -gn;
if te < 0 then
begin
if g5 = 0 then te := te + 1;
end;
tn := int(tn / 2.5) * 2.5;

lat := (te) + (tn / 60);

end;