Instant Veins 4.7-i1 Localization Time of Arrival - omnet++

Question

I am a masters student working on localization, using ranging (time of arrival between vehicle and RSU) and relative location (Using emulated Inertial Navigation System).
I have done an implementation of my kalman filter based localization logic on Matlab, now I would like to implement this on veins. I want only the RSU to send out a message comprising of its location and ID
1) I know that i can use
double Coord = mobility->getCurrentPosition().x;
double Coord = mobility->getCurrentPosition().y;
to the location of RSU(and my vehicle as well), I do not understand how I should assign these coordinates to the message. I cannot use sstream since I understand that the message are supposed to be of type const char *
Thanks for any input
Edit 1: So this is what my new code on RSU looks like:
#include "RsuScOne.h"
#include <sstream>
Define_Module(RsuScOne);
void RsuScOne::initialize(int stage) {
BaseWaveApplLayer::initialize(stage);
if (stage == 0) {
//Initializing members and pointers of your application goes here
//WaveShortMessage* wsm = new WaveShortMessage();
EV << "Initializing " << std::endl;
}
else if (stage == 1) {
//Initializing members that require initialized other modules goes here
}
}
void RsuScOne::finish() {
BaseWaveApplLayer::finish();
//statistics recording goes here
cancelEvent(sendWSAEvt);
}
void RsuScOne::onWSM(WaveShortMessage* wsm) {
//Your application has received a data message from another car or RSU
//code for handling the message goes here, see TraciDemo11p.cc for examples
populateWSM(wsm);
std::stringstream ss;
ss<<mobility->getCurrentPosition().x<<mobility->getCurrentPosition().y;
wsm->setWsmData(ss.str().c_str());
scheduleAt(simTime()+par("beaconInterval").doubleValue(), sendWSAEvt);
EV<<wsm;
}
void RsuScOne::handleSelfMsg(cMessage* msg) {
BaseWaveApplLayer::handleSelfMsg(msg);
}
But I realize that all that being done now is my RSU constantly sending a generic BSM, Why is this so?