以下の続きになります。
3GIM > Arduino UNO R3 から3G通信 - Qiita

// 3GIM(V2) sample sketch -- getLocation

# include <SoftwareSerial.h>
# include "a3gim.h"

# define baudrate 	9600UL
# define baudrate_3gim   115200
const int powerPin = 7;     // 3gim power pin(If not using power control, 0 is set.)

void setup()
{
  Serial.begin(baudrate);
  delay(3000);    // Wait for start serial monitor
  Serial.println("GPS Ready.");

  Serial.print("Initializing.. ");
  if (a3gs.start(powerPin) == 0 && a3gs.begin(0, baudrate_3gim) == 0) {
    Serial.println("Succeeded. It maybe takes several minutes.");
    char lat[15], lng[15];
    if (a3gs.getLocation(a3gsMPBASED, lat, lng) == 0) {
      Serial.print("OK: ");
      Serial.print(lat);
      Serial.print(", ");
      Serial.println(lng);
    }
    else
      Serial.println("Sorry, I don't know this location.");
  }
  else
    Serial.println("Failed.");

  Serial.println("Shutdown..");
  a3gs.end();
  a3gs.shutdown();
}

void loop()
{
}

// END

結果

Ready.
Initializing.. Succeeded. It maybe takes several minutes.
OK: 31.790, 56
Shutdown..