Update README.md

Author: fercabe

README.md

@@ -1,7 +1,27 @@
 # DLL: Direct Lidar Localization
 
-Robot localization based on direct registration of 3D LIDAR on maps.
+## Summary
+
+This package presents DLL, a direct map-based localization technique using 3D LIDAR for its application to aerial robots. DLL implements a point cloud to map registration based on non-linear optimization of the distance of the points and the map, thus not requiring  features, neither point correspondences. Given an initial pose, the method is able to track the pose of the robot by refining the predicted pose from odometry. The method performs much better than Monte-Carlo localization methods and achieves comparable precision to other optimization-based approaches but running one order of magnitude faster. The method is also robust under odometric errors. 
+
+DLL is fully integarted in Robot Operating System (ROS). It follows the general localization apparoch of ROS, DLL makes use of sensor data to compute the translation that better fits the robot odometry TF into the map. Although an odometry system is recommended for fast and accurate localization, DLL also performs well without odometry information if the robot moves smoothly. 
 
 ## Dependencies
+There are not hard dependencies except for Google Ceres Solver and 
+ - ceres: Follow installation instructions for Google Ceres (http://ceres-solver.org/installation.html)
+ - ROS: The package has been tested in ROS Melodic under Ubunto 18.04. Follow installation instruction from ROS (http://wiki.ros.org/melodic/Installation/Ubuntu)
+
+## Compilation
+Download this source code into the src folder of your catkin worksapce:
+```
+$ cd catkin_ws/src
+$ git clone https://github.com/robotics-upo/dll
+```
+Compile the project:
+```
+$ cd catkin_ws
+$ source devel/setup.bash
+$ catkin_make
+```
 
- - ceres: Follow in installation instructions for Google Ceres
+## How to use DLL