Example for MapMark.inc

#include <a_samp>
#include <mapmark>

new Float:GPSx[MAX_PLAYERS];
new Float:GPSy[MAX_PLAYERS];
new bool:GPSon[MAX_PLAYERS];

public OnPlayerCommandText(playerid, cmdtext[])
{
    if (strcmp("/map", cmdtext, true) == 0)
    {
        SendClientMessage(playerid,0x00FF00FF,"Mark a position on the map to transmit it to the server!");

        SetPlayerMarkingMap(playerid,1);

        return 1;
    }

    if (strcmp("/gps", cmdtext, true) == 0)
    {
        SendClientMessage(playerid,0x00FF00FF,"Mark a position on the map to transmit it to the server!");

        SetPlayerMarkingMap(playerid,2);

        return 1;
    }
    return 0;
}
public OnPlayerMarkMap(playerid, MarkID, Float:X, Float:Y, Float:Z)
{
    if(MarkID == 1)
    {
        SendClientMessage(playerid,0xFF0000FF,"MapIcon successfully set.");
        SetPlayerMapIcon(playerid,1,X,Y,Z,32,0,MAPICON_GLOBAL);
    }
    if(MarkID == 2)
    {
        GPSx[playerid] = X;
        GPSy[playerid] = Y;
        GPSon[playerid] = true;
        SetTimerEx("GPSTimer",3000,0,"d",playerid);
    }
}

forward GPSTimer(playerid);
public GPSTimer(playerid)
{
    if(!GPSon[playerid]) return 0;

    new Float: Distance;
    new Float:X, Float:Y, Float:Z;

    GetPlayerPos(playerid,X,Y,Z);
    if(IsPlayerInAnyVehicle(playerid)) GetVehiclePos(GetPlayerVehicleID(playerid),X,Y,Z);

    Distance = GDBP(X,Y,Z,GPSx[playerid],GPSy[playerid],Z);

    if(Distance > 10.0)
    {
        new str[128];

        format(str,sizeof(str),"~r~-GPS-~n~~g~Distance: %.2f",Distance);
        GameTextForPlayer(playerid,str,1000,4);
        SetTimerEx("GPSTimer",500,0,"d",playerid);
    }
    else
    {
        GameTextForPlayer(playerid,"~r~-GPS-~n~~g~Destination reached.",4000,4);
        GPSon[playerid] = false;
    }
    return 1;
}