diff --git a/GPU_version/vio/src/frame.cpp b/GPU_version/vio/src/frame.cpp
index 0e52a6a..966a668 100644
--- a/GPU_version/vio/src/frame.cpp
+++ b/GPU_version/vio/src/frame.cpp
@@ -145,14 +145,12 @@ void Frame::removeKeyPoint(Feature* ftr)
 bool Frame::isVisible(const Vector3d& xyz_w) const
 {
     if(!id_)return false;
-    std::cerr<<"148is\t";
+    usleep(1000);
     SE3 tem=this->se3();
-    std::cerr<<"150is\t";
+    assert(!xyz_w.hasNaN());
   Vector3d xyz_f = tem*xyz_w;
-    std::cerr<<"152is\t";
   if(xyz_f.z() < 0.0)
     return false; // point is behind the camera
-    std::cerr<<"153is\t";
   Vector2d px = f2c(xyz_f);
   if(px[0] >= 0.0 && px[1] >= 0.0 && px[0] < cam_->width() && px[1] < cam_->height())
     return true;
diff --git a/GPU_version/vio/src/frame_handler_mono.cpp b/GPU_version/vio/src/frame_handler_mono.cpp
index 5844b19..21daefa 100644
--- a/GPU_version/vio/src/frame_handler_mono.cpp
+++ b/GPU_version/vio/src/frame_handler_mono.cpp
@@ -168,7 +168,7 @@ FrameHandlerBase::UpdateResult FrameHandlerMono::processFrame()
   new_frame_->Cov_ = init_f.first;
   // sparse image align
   SparseImgAlignGpu img_align(Config::kltMaxLevel(), Config::kltMinLevel(),30, SparseImgAlignGpu::GaussNewton, false,gpu_fast_);
-  img_align.run(last_frame_, new_frame_);
+  if(!img_align.run(last_frame_, new_frame_))new_frame_->T_f_w_=init_f.second;
   reprojector_.reprojectMap2(new_frame_, last_frame_,overlap_kfs_);
   //assert (false);
   int n_point=0;
diff --git a/GPU_version/vio/src/map.cpp b/GPU_version/vio/src/map.cpp
index 51fef6e..0b3a916 100644
--- a/GPU_version/vio/src/map.cpp
+++ b/GPU_version/vio/src/map.cpp
@@ -120,6 +120,7 @@ void Map::getCloseKeyframes(
     {
       if(keypoint == nullptr)
           continue;
+      if(keypoint->point==NULL)continue;
       if(frame->isVisible(keypoint->point->pos_))
       {
         close_kfs.push_back(
diff --git a/GPU_version/vio/src/reprojector.cpp b/GPU_version/vio/src/reprojector.cpp
index 795b82a..9dad605 100644
--- a/GPU_version/vio/src/reprojector.cpp
+++ b/GPU_version/vio/src/reprojector.cpp
@@ -124,6 +124,7 @@ namespace vio {
             FramePtr frame,
             FramePtr last_frame,
             std::vector<std::pair<FramePtr, std::size_t> > &overlap_kfs) {
+        if(frame->id_<1)return;
         resetGrid();
         cv::Mat descriptors_cur;
         std::vector<cv::KeyPoint> keypoints_cur;