SIM808 HTTP request with gps data

Using Arduino Sensors
1

I´m using an Arduino Mega 2560 with the SIM808 module. I want to send a HTTP Request with my current GPS coordinates. Viewed separately (in two sketches) I can use both functions. If I combine both sketches the module does not receive GPS data anymore.

Which changes are necessary, so that both function can work together?

#include DFRobot_SIM808 sim808(&Serial);

char buffer[512];

void setup(){
Serial.begin(9600);

//******** Initialize sim808 module *************
while(!sim808.init()) {
  delay(1000);
  Serial.print("Sim808 init error\r\n");
}
  delay(3000);

  //*********** Attempt DHCP *******************
  while(!sim808.join(F("internet.eplus.de"))) {
  Serial.println("Sim808 join network error");
  delay(2000);
}


//************ Successful DHCP ****************
Serial.print("IP Address is ");
Serial.println(sim808.getIPAddress());


//************* Turn on the GPS power************

  if( sim808.attachGPS())
  Serial.println("Open the GPS power success");
  else 
  Serial.println("Open the GPS power failure");
  delay(2000);  

}

void loop(){

  tcp();
  delay(2000);
}


void tcp()
{

// Update the GPS data
float lati, longi;
if (sim808.getGPS()) {
    lati = sim808.GPSdata.lat;
    longi = sim808.GPSdata.lon;
    sim808.detachGPS();
}
else {
    // No gps, abort
    return;
}


//*********** Establish a TCP connection ************

if (!sim808.connect(TCP,"100.100.100.100", 80)) {
   Serial.println("Connect error");
   return;
}
else {
   Serial.println("Connect POPO success");
}

//*********** Send a GET request *****************

char http_cmd[100];
sprintf(http_cmd, "GET /api/v1/Status?latitude=%f&longitude=%f HTTP/1.0\r\n\r\n\0", lati, longi);
sim808.send(http_cmd, strlen(http_cmd));



//************* Close TCP or UDP connections **********
sim808.close();

//*** Disconnect wireless connection, Close Moving Scene *******
sim808.disconnect();
}