如何在VEINS中获取指定时间车辆坐标并计算间距？Veins4.6环境求助

Hey there, let's tackle this problem step by step. I've worked with Veins 4.6, SUMO 0.25, and OMNeT++ 5.2 before, so I have some solid ideas on what might be going wrong and how to fix it.

First, Let's Diagnose the Coordinate Issue #

The "abnormally small coordinates" for veh1 usually stems from one of these common pitfalls:

• You're using the wrong method to fetch coordinates (bypassing Veins' built-in coordinate conversion)
• veh1 hasn't started moving in SUMO yet (e.g., its depart time is later than your query time)
• You're querying a non-existent vehicle ID (double-check SUMO's route file for exact IDs)
• The handlePositionUpdate() function isn't triggering correctly for veh1

Proper Way to Get Positions at a Specific Time #

Instead of relying solely on handlePositionUpdate() (which fires on every position tick), use an OMNeT++ timer to query positions exactly when you need them. Here's a complete implementation:

Step 1: Update the Header File (TraCIDemo11p.h)

Add a timer member variable to trigger your position query:

class TraCIDemo11p : public BaseWaveApplLayer {
    // ... existing code ...
    private:
        cMessage* positionQueryTimer; // Timer to trigger position check
};

Step 2: Initialize the Timer in initialize()

Set up the timer to fire at your target simulation time (e.g., 10.0 seconds):

void TraCIDemo11p::initialize(int stage) {
    BaseWaveApplLayer::initialize(stage);
    if (stage == 0) {
        // ... existing initialization code ...
        // Schedule position query at 10.0s (adjust to your target time)
        positionQueryTimer = new cMessage("positionQuery");
        scheduleAt(simTime() + 10.0, positionQueryTimer);
    }
}

Step 3: Handle the Timer and Query Positions

In handleMessage(), add logic to fetch both vehicles' coordinates and calculate distance:

void TraCIDemo11p::handleMessage(cMessage* msg) {
    if (msg == positionQueryTimer) {
        // Get current vehicle's mobility module and position
        TraCIMobility* mobility = TraCIMobilityAccess().get(getParentModule());
        Coord myPos = mobility->getCurrentPosition();
        std::string myId = getParentModule()->getFullName();
        EV_INFO << "[" << myId << "] Position at " << simTime() << ": " << myPos << endl;

        // Fetch the other vehicle's position via TraCI
        TraCICommandInterface* traci = mobility->getCommandInterface();
        const std::string targetVehId = "veh1"; // Match SUMO's vehicle ID

        if (traci->vehicleExists(targetVehId)) {
            TraCICommandInterface::Vehicle* targetVeh = traci->vehicle(targetVehId);
            Coord targetPos = targetVeh->getPosition();
            EV_INFO << "[" << targetVehId << "] Position at " << simTime() << ": " << targetPos << endl;

            // Calculate distance between the two vehicles
            double distance = myPos.distance(targetPos);
            EV_INFO << "Distance between " << myId << " and " << targetVehId << ": " << distance << " meters" << endl;
        } else {
            EV_WARN << "Vehicle " << targetVehId << " does not exist at time " << simTime() << endl;
        }

        // Optional: Reschedule the timer if you need repeated checks
        // scheduleAt(simTime() + 5.0, positionQueryTimer);
    } else {
        // Pass other messages to the base class
        BaseWaveApplLayer::handleMessage(msg);
    }
}

Step 4: Fix handlePositionUpdate() (If You Still Want to Use It)

If you prefer using handlePositionUpdate(), make sure you're fetching coordinates correctly (avoid direct member variable access):

void TraCIDemo11p::handlePositionUpdate(cObject* obj) {
    BaseWaveApplLayer::handlePositionUpdate(obj);

    TraCIMobility* mobility = TraCIMobilityAccess().get(getParentModule());
    Coord currentPos = mobility->getCurrentPosition();
    std::string myId = getParentModule()->getFullName();
    EV_INFO << "[" << myId << "] Position updated at " << simTime() << ": " << currentPos << endl;

    // Fetch veh1's position here too, same as above
    TraCICommandInterface* traci = mobility->getCommandInterface();
    if (traci->vehicleExists("veh1")) {
        TraCICommandInterface::Vehicle* veh1 = traci->vehicle("veh1");
        Coord veh1Pos = veh1->getPosition();
        double dist = currentPos.distance(veh1Pos);
        EV_INFO << "Distance to veh1: " << dist << endl;
    }
}

Key Checks to Fix the Small Coordinate Issue #

• Verify SUMO's Vehicle Configuration: Check your .rou.xml file to ensure veh1 has a valid depart time (earlier than your query time) and a proper route.
• Use Correct Coordinate Methods: Always use getCurrentPosition() (from TraCIMobility) or getPosition() (from TraCICommandInterface::Vehicle)—these handle SUMO-to-OMNeT++ coordinate conversion automatically.
• Validate Vehicle IDs: Ensure the ID you're using in code exactly matches the ID in SUMO (case-sensitive!).

内容的提问来源于stack exchange，提问作者Toothless