SLAM noob here but trying to implement an algorithm that fuses odometry data and mapping based on wifi signal strengths for a 2D robot.
1) After various readings of different resources, I came across this - http://www.qucosa.de/fileadmin/data/qucosa/documents/8644/Dissertation_Niko_Suenderhauf.pdf that explained what sensors are used in mapping and how they are categorized.
There are range-bearing sensors (stereo cameras,RGB-d cameras) that provide both distance and angle (range and bearing), from which is easy to locate (x,y) coordinates of landmarks ---> I can develop a map.
But in case I'm using wifi signal strengths (Received signal strengths) etc, in which case it is range-only (meaning, I can only establish from a robot pose(x,y,theta) as to how far this signal is coming from), how am I developing a map at all?
My question is similar to this - What algorithm can I use for constructing a map of an explored area using a number of ultrasound sensors? but not quite same.
Even if I were using IMU/GPS, how am I using GPS to develop a map? What is my state space there? If I am getting GPS signals / wifi signals/ radio signals, am I estimating the transmitter/AP's location as the map? or the walls of a room I'm navigating in, as a map?
A lot of SLAM literature talks about motion model and measurement model, the former gives me the pose of the robot quite easily because of the odometry and imu.
The latter though is more for development of a map. Am I right in understanding this? If yes, say a] I have walls in a room and I'm using Lidar scanner - this still gives me the location of the wall using the number of beams that give me bearing, and the average distance from all the beams.
b] Or if I have just a single laser scanner, I can still use a camera (distance) and the heading of the robot to calculate the location of wall (the map). https://shaneormonde.wordpress.com/2014/01/25/webcam-laser-rangefinder/#more-403
But If I have wireless signal strengths, I have a distance (distance of the transmitter from which I'm getting the RSS, not the distance of the wall) as to where they are coming from. But how am I estimating the location of walls here?
2) What does the term "correspondences" mean in SLAM literature?