# Map-Matching-Based Localization Using Camera and Low-Cost GPS for Lane-Level Accuracy +
## 1 Introduction  
Autonomous driving or drive-less car system is a promising technology for the future transportation that potentially has the capacity to improve road safety and to have a better mobility. Self-driving cars promise to bring a number of benefits to society, including prevention of road accidents, optimal fuel usage, comfort and convenience [1]. An autonomous vehicle is a car that can drive itself without human intervention. It is therefore obvious that for this type of vehicle, it must be able to know its location very precisely and very quickly in order to know where it is on the road. Indeed, with such a steering system, the driving of an autonomous vehicle is automated. This system must enable it to travel and make decisions without the driver's intervention. In other words, an autonomous vehicle must be able to navigate independently without human intervention to reach a predetermined destination from the current location. When it comes to navigation task, it requires the understanding of situation of the surrounding environment and the knowing of its current location, which is the actual position relative to a predefined path toward the destination. Determining the actual vehicle position, known as the vehicle localization, is a crucial task in autonomous car. An autonomous car must be able to localize precisely its position in order to perform various maneuvers such as changing lanes and turning. As humans, we can drive much faster and safer if we are familiar with the route or if we have been provided sufficient road signs and obstacles to guide us in driving on unfamiliar roads. We already know what to expect for the upcoming situations and conditions such as where the intersections and stop signs are, where and when to take a turn, turn left or turn right, and etc. Likewise human, autonomous cars can drive more efficiently if we provide them with sufficient information that can tell them where to look and what actions to expect. An autonomous car can benefit from all this information provided it is equipped with a precise localization system. Since the navigation goal is to reach a predetermined destination location from the start position, localization can guide the vehicle to achieve the destination location in performing the navigation task. With a precise information of its position, the vehicle will be able to easily manage the maneuvers. The intersections, stop signs, curbs, lanes and turns can be handled easily because the vehicle knows where, when and what actions is expected. Figure 1 shows an illustration of the upcoming events provided by a digital map to the autonomous vehicle. With this information, the vehicle knows what actions must be taken in the next few seconds. In order to perform complex maneuvers, an autonomous vehicle needs an accurate and robust real-time localization. Nowadays, localization has emerged as one of the crucial issues in drive-less cars development [3]. A lot of research has been done over the last decade on vehicle localization systems. The GNSS (i.e., global navigation satellite system) is one of the most widely used sensors for localizing the vehicle's positions, such as the global positioning system (GPS). However, using only GPS solution for the localization system is not optimal to support the AV maneuvers. The accuracy of GPS often degrades due to poor satellite constellation geometry, shadowing, and multi-path propagation of satellite signals [4]. To address the GPS positioning errors, complementary systems depending on dead-reckoning sensors including accelerometer, gyroscope, and odometers have been proposed. Figure 1: An illustration of the expected upcoming events that the autonomous car must be aware of. By having an accurate localization system, the vehicle can precisely locate the next upcoming events, so that the vehicle knows what action must be taken in the next seconds. Image source: extracted from Bosch’s video [2]. However, the systems using these kinds of sensors have some drawbacks.