Landmark-based navigation systems have proven benefits relative to traditional turn-by-turn systems that use street names and distances. However, one obstacle to the implementation of landmark-based navigation systems is the complex challenge of selecting salient local landmarks at each decision point for each user. In this paper, we present Pharos, a novel system that extends turn-by-turn navigation instructions using a single global landmark (e.g. the Eiffel Tower, the Burj Khalifa, municipal TV towers) rather than multiple, hard-to-select local landmarks. We first show that our approach is feasible in a large number of cities around the world through the use of computer vision to select global landmarks. We then present the results of a study demonstrating that by including global landmarks in navigation instructions, users navigate more confidently and build a more accurate mental map of the navigated area than using turn-by-turn instructions.
As global landmarks can be seen from longer distances and therefore the mere location information is not sufficient, visibility tests are always necessary. Visual landmark detection is related to the problems of location recognition, object recognition and image retrieval. For computer vision it is common to use simple image features, such as edges or corners in an image. For example, SIFT @cite_20 , SURF @cite_2 and ORB @cite_32 are popular image feature descriptors, which can be used together with machine learning approaches, e.g. support vector machines @cite_8 to predict whether an image contains a particular landmark. Most recently convolutional neural networks @cite_12 have become very popular; they work directly on the pixel data.
@cite_8 @cite_32 @cite_2 @cite_20 @cite_12
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The recognition of a place depicted in an image typically adopts methods from image retrieval in large-scale databases. First, a query image is described as a “bag-of-features” and compared to every image in the database. Second, the most similar images are passed to a geometric verification stage. However, this is an inefficient approach when considering that some database images may be almost identical, and many image features may not repeatedly occur. We address this issue by clustering similar database images to represent distinct scenes, and tracking local features that are consistently detected to form a set of real-world landmarks. Query images are then matched to landmarks rather than features, and a probabilistic model of landmark properties is learned from the cluster to appropriately verify or reject putative feature matches. We present novelties in both a bag-of-features retrieval and geometric verification stage based on this concept. Results on a database of 200K images of popular tourist destinations show improvements in both recognition performance and efficiency compared to traditional image retrieval methods. Traditional approaches to simultaneous localization and mapping (SLAM) rely on low-level geometric features such as points, lines, and planes. They are unable to assign semantic labels to landmarks observed in the environment. Furthermore, loop closure recognition based on low-level features is often viewpoint-dependent and subject to failure in ambiguous or repetitive environments. On the other hand, object recognition methods can infer landmark classes and scales, resulting in a small set of easily recognizable landmarks, ideal for view-independent unambiguous loop closure. In a map with several objects of the same class, however, a crucial data association problem exists. While data association and recognition are discrete problems usually solved using discrete inference, classical SLAM is a continuous optimization over metric information. In this paper, we formulate an optimization problem over sensor states and semantic landmark positions that integrates metric information, semantic information, and data associations, and decompose it into two interconnected problems: an estimation of discrete data association and landmark class probabilities, and a continuous optimization over the metric states. The estimated landmark and robot poses affect the association and class distributions, which in turn affect the robot-landmark pose optimization. The performance of our algorithm is demonstrated on indoor and outdoor datasets. Facial landmark detection is a fundamental step for many tasks in computer vision such as expression recognition and face alignment. In this paper, we focus on the detection of landmarks under realistic scenarios that include pose, illumination and expression challenges as well as blur and low-resolution input. In our approach, an n-point shape of point-landmarks is represented as a union of simpler polygonal sub-shapes. The core idea of our method is to find the sequence of deformation parameters simultaneously for all sub-shapes that transform each point-landmark into its target landmark location. To accomplish this task, we introduce an agglomerate of fern regressors. To optimize the convergence speed and accuracy we take advantage of search localization using component-landmark detectors, multi-scale analysis and learning of point cloud dynamics. Results from extensive experiments on facial images from several challenging publicly available databases demonstrate that our method (ACFeR) can reliably detect landmarks with accuracy comparable to commercial software and other state-of-the-art methods. This paper proposes a new framework for visual place recognition that incrementally learns models of each place and offers adaptability to dynamic elements in the scene. Traditional Bag-Of-Words (BOW) image-retrieval approaches to place recognition typically treat images in a holistic manner and are not capable of dealing with sub-scene dynamics, such as structural changes to a building facade or seasonal effects on foliage. However, by treating local features as observations of real-world landmarks in a scene that is observed repeatedly over a period of time, such dynamics can be modelled at a local level, and the spatio-temporal properties of each landmark can be independently updated incrementally. The method proposed models each place as a set of such landmarks and their geometric relationships. A new BOW filtering stage and geometric verification scheme are introduced to compute a similarity score between a query image and each scene model. As further training images are acquired for each place, the landmark properties are updated over time and in the long term, the model can adapt to dynamic behaviour in the scene. Results on an outdoor dataset of images captured along a 7 km path, over a period of 5 months, show an improvement in recognition performance when compared to state-of-the-art image retrieval approaches to place recognition.