Gao Xiang slam14 lecture - note 1

• Gao Xiang is the master B The lecture video of the station , It is suggested that before watching the video 《 Vision SLAM Fourteen speak 》 Go through it
• 《 Vision SLAM Fourteen speak 》 The code is hosted in by chapter here
  preparation ：
• How to be in windows Lower installation VMware And create linux virtual machine (ubuntu)

slam Basic concepts

• slam： A body equipped with a specific sensor , Without prior environmental information , During exercise Model the environment , meanwhile Estimate your movement
• Map model ： A generalized map , Baidu map is a kind of map , Discrete points in the space environment , For positioning , stay slam It is also called map
• slam Application field ： robot 、 Unmanned aerial vehicle (uav) 、 unmanned 、 Augmented reality
• Introductory books ：The Bible: Multiple View Gemetry in Computer Vision
  State Estimation for Robotics: A Matrix Lie Group Approch
  Probabilistic Robotics
• SLAM Two related types of sensors ：
  Installed in the environment , Such as QR code identification 、GPS、 Guide 、 Magnetic stripe
  Carried on the robot body , Such as IMU, laser 、 The camera
• Vision SLAM The camera ：
  Monocular ： No depth
  Binocular ： Calculate the depth by parallax stereo
  RGBD： Measure the depth by physical methods , Measuring depth by physical means , Such as structured light
  ToF, Active measurement , High power consumption , The depth value is accurate , The depth of each pixel can be measured ,
  Small range , Generally tens of meters , Susceptible to interference , It is difficult to apply outdoors （ Structured light is easily disturbed by natural light ）
• Vision SLAM frame ： front end VO, Back end Optimization, Loop back detection ：Loop Closing, Drawing ：Mapping

slam The simplest description of the problem

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Knowledge of linear algebra

The outer product of a vector （ Cross riding ）
summary ： The outer product of two vectors , Also called cross multiplication , The result is a vector, not a scalar , The outer product of two vectors is perpendicular to the coordinate plane composed of these two vectors .
Definition ： vector a And b Outer product of a×b It's a vector , Its length is equal to |a×b|=|a||b|sin(a,b), Its direction is orthogonal to a And b, also ,(a,b,a×b) Form a right-handed system . Special ,0×a=a×0, Besides , For any vector a,a×a=0.
For vector a Sum vector b：

a and b The outer product formula of is ：

among ：

The geometric meaning of vector outer product ：
（ in fact , There is no geometric meaning above three dimensions , Therefore, the discussion of geometric meaning in linear algebra is of little significance , It only plays an auxiliary role in understanding ）
In three-dimensional geometry , vector a Sum vector b The result of the outer product of is a normal vector , The vector is perpendicular to a and b A plane of vectors . stay 3D In iconography , The concept of outer product is very useful , You can use the outer product of two vectors , Generate a third perpendicular to a,b The normal vector of , To build X、Y、Z Coordinate system . As shown in the figure below