Is there any way to do feature-based localization using OpenCV?

Question

Im using OpenCV feature detection to estimate robot position based on comparison of LIDAR result and virtual map. I've try using orb feature detection followed by flannbasedmatcher, but the match result gone wrong. here's some of my code

Ptr<ORB> orb_a = ORB::create();
Ptr<ORB> orb_b = ORB::create();
vector <cv::KeyPoint> kp1,kp2;
Mat desc1,desc2;

/* set orb :
   1. ORB name
   2. nfeatures
   3. Nlevels
   4. EdgeThreshold
   5. First Level
   6. WTA
   7. Score Type
   8. Patchsize
   9. Scale Factor  */
Mat hmap,hlidar;

setORB(orb_a,500,8,100,0,4,ORB::HARRIS_SCORE,31,1.1);   //map
orb_a->detectAndCompute(lidarmap,noArray(),kp1,desc1);
  drawKeypoints(lidarmap,kp1,hmap,Scalar::all(-1),DrawMatchesFlags::DEFAULT);

setORB(orb_b,50,8,30,0,4,ORB::HARRIS_SCORE,10,1.5); //lidar
orb_b->detectAndCompute(lidarused,noArray(),kp2,desc2);
  drawKeypoints(lidarused,kp2,hlidar,Scalar::all(-1),DrawMatchesFlags::DEFAULT);

//flann

FlannBasedMatcher matcher;
std::vector<DMatch>matches;
matcher.match (desc1,desc2,matches);

double maxdist = 0, mindist = 100000;

for (int i = 0; i< desc1.rows; i++)
        {
        double dist = matches[i].distance;
        if (dist<mindist) mindist = dist;
        if (dist>maxdist) maxdist = dist;
        }
if (mindist<0.02) mindist = 0.02;

printf ("min : %7.3f \t max : %7.3f \n",mindist,maxdist);

vector <DMatch> good_matches;

for (int i=1; i<desc1.rows; i++)
        {
    if (matches[i].distance >= 2*mindist && matches[i].distance<maxdist/2)
            {
            good_matches.push_back (matches[i]);
            }
        }
Mat imgmatches;
drawMatches (lidarmap,kp1,
             lidarused,kp2,
             good_matches,imgmatches,
             Scalar::all(-1), Scalar::all(-1),
             vector<char>(),DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS);

here's the result. Detection seems okay, but it's terrible when i rotate second image

Is flann matcher only works on unscaled and unrotated image? Can i use flann to match bicolor image (BW) ? or can somebody point where i'm doing it wrong? thanks in advance

score 1 · Accepted Answer · answered Jan 23 '16 at 16:56

1

From my experience ORB features are too weak to be used with FLANN. Try your code with sift or surf. If it works you can try to tweak in order to use ORB.

Another option is to use DBoW2 Library. They have descent results with binary features.

answered Jan 23 '16 at 16:56

weblucas

46
2

i change ORB with SURF, and it works better. but the problem still same. i got wrong detection using FLANN matcher. how to improve the result of FLANN? – duck Feb 22 '16 at 08:34

Is there any way to do feature-based localization using OpenCV?

1 Answers1