Least-cost Routes Research Articles

Methodologies for Addressing the Performance Issues of Routing in Mobile Ad hoc Networks: A Review

The objective of this review article is to offer an insight into the performance issues pertinent to routing in Mobile Ad hoc Networks. This work has studied the approaches for solving the performance issues such as changes in topology, energy consumption of mobile nodes, delay, routing overhead, message delivery time, throughput, packet delivery ratio, security of networks and mobility management. To provide a perception of solutions for these issues, this study concentrates on various methodologies such as Effective Hierarchical Routing Algorithm, Link Stability with Energy Aware Multipath Routing protocol, Path Encounter Rate metric and Trust-based Source Routing protocol. Effective Hierarchical Routing Algorithm computes the route and has decreased the load of routing protocols. Link Stability with Energy Aware Multipath Routing protocol finds routes with small delay. Delivery ratio of packet in LSEA is improved on par with Ad hoc On-demand Distance Vector Routing (AODV). Delivery ratio of packets in LSEA was enhanced by 40%. To get an efficient metric for routing in high mobility situations, Path Encounter Rate metric was proposed. Throughput achieved with this metric was 30% higher than those obtained by the hop-count metric. To choose a least-cost route with security constraints, TSR was proposed. TSR has improved the packet delivery ratio, ratio of identifying the malicious nodes as well as network throughput. This review of different methods can be used by researchers to find a better solution to these issues.

On a class of three-dimensional transshipment problems

The transshipment technique is used to find the shortest route from one point in a network to another point and is very useful to reduce the cost of transportation. In this article, we have formulated a three-dimensional linear transshipment problem. Sometimes, because of the budget/political constraints, the total flow of transportation is specified by some external decision maker which thereby results in restricted and enhanced flow in the market. The optimal solution of such problems is of practical interest to the decision maker and thus has motivated us to discuss such problems as a particular case of the original problem. The optimal solution of the specified problem is obtained by transforming it into an equivalent transportation problem by adding an additional row and a column and avoids the necessity of determining a least-cost route for every origin-destination pair. The algorithm is easy to understand and apply and it can serve the managers by providing a solution to a variety of production-distribution problems having heterogeneous commodities. Numerical examples are also included to support the theory.

Landscapes of State Formation: Geospatial Analysis of Aksumite Settlement Patterns (Ethiopia)

Landscape-scale dynamics of the Kingdom of Aksum and its territories are exceptionally well-suited to help refine understanding of ancient complex polities in Africa and beyond. Archaeological explanations of ancient state formation have long centered on a small number of so-called primary cases that are thought to have inspired the rise of descendant, secondary states. Yet the rise of Aksum shows both local and multiregional influences which contradict diffusion and independent-origination focused explanations. Over four summer field-seasons (2005–2008), the Eastern Tigrai Archaeological Project (ETAP) targeted a 196-km2 inland area between Aksum and the Red Sea recording 137 sites, including 7 ancient towns larger than 6 ha. We report results of spatial analysis of site sizes, site clustering, trade routes, and spatial associations of sites with landforms and hydrology. Least-cost path GIS analysis of trade routes from Adulis to Aksum is broadly consistent with the reports of the Periplus Maris Erythraei, yet many travelers may have opted for a more circuitous highland itinerary rather than a direct least-cost route. Rank-size analysis reveals no conclusive evidence of site-size hierarchies suggesting, at least in this area, complex polities may not be characterized by clear categories of different size settlements. Ripley’s K multiscalar cluster analysis shows a spatial distribution of sites lacking pronounced clustering/dispersion, indicating that settlement locations were not determined predominantly by the proximity of neighbors. Finally, satellite imagery modeling shows statistically significant associations between settlements, landforms, and water-rich areas most amenable to high-productivity agriculture, showing environmental conditions played a pivotal role in shaping landscape-scale site patterning.

Human-induced changes in landscape configuration influence individual movement routines: lessons from a versatile, highly mobile species.

Landscape conversion by humans may have detrimental effects on animal populations inhabiting managed ecosystems, but human-altered areas may also provide suitable environments for tolerant species. We investigated the spatial ecology of a highly mobile nocturnal avian species–the red-necked nightjar (Caprimulgus ruficollis)–in two contrastingly managed areas in Southwestern Spain to provide management recommendations for species having multiple habitat requirements. Based on habitat use by radiotagged nightjars, we created maps of functional heterogeneity in both areas so that the movements of breeding individuals could be modeled using least-cost path analyses. In both the natural and the managed area, nightjars used remnants of native shrublands as nesting sites, while pinewood patches (either newly planted or natural mature) and roads were selected as roosting and foraging habitats, respectively. Although the fraction of functional habitat was held relatively constant (60.9% vs. 74.1% in the natural and the managed area, respectively), landscape configuration changed noticeably. As a result, least-cost routes (summed linear distances) from nest locations to the nearest roost and foraging sites were three times larger in the natural than in the managed area (mean ± SE: 1356±76 m vs. 439±32 m). It seems likely that the increased proximity of functional habitats in the managed area relative to the natural one is underlying the significantly higher abundances of nightjars observed therein, where breeders should travel shorter distances to link together essential resources, thus likely reducing their energy expenditure and mortality risks. Our results suggest that landscape configuration, but not habitat availability, is responsible for the observed differences between the natural and the managed area in the abundance and movements of breeding nightjars, although no effect on body condition was detected. Agricultural landscapes could be moderately managed to preserve small native remnants and to favor the juxtaposition of functional habitats to benefit those farm species relying on patchy resources.

A new method for deriving glacier centerlines applied to glaciers in Alaska and northwest Canada

Abstract. This study presents a new method to derive centerlines for the main branches and major tributaries of a set of glaciers, requiring glacier outlines and a digital elevation model (DEM) as input. The method relies on a "cost grid–least-cost route approach" that comprises three main steps. First, termini and heads are identified for every glacier. Second, centerlines are derived by calculating the least-cost route on a previously established cost grid. Third, the centerlines are split into branches and a branch order is allocated. Application to 21 720 glaciers in Alaska and northwest Canada (Yukon, British Columbia) yields 41 860 centerlines. The algorithm performs robustly, requiring no manual adjustments for 87.8% of the glaciers. Manual adjustments are required primarily to correct the locations of glacier heads (7.0% corrected) and termini (3.5% corrected). With corrected heads and termini, only 1.4% of the derived centerlines need edits. A comparison of the lengths from a hydrological approach to the lengths from our longest centerlines reveals considerable variation. Although the average length ratio is close to unity, only ~ 50% of the 21 720 glaciers have the two lengths within 10% of each other. A second comparison shows that our centerline lengths between lowest and highest glacier elevations compare well to our longest centerline lengths. For > 70% of the 4350 glaciers with two or more branches, the two lengths are within 5% of each other. Our final product can be used for calculating glacier length, conducting length change analyses, topological analyses, or flowline modeling.

Reinforcement Learning for Routing in Cognitive Radio Ad Hoc Networks

Cognitive radio (CR) enables unlicensed users (or secondary users, SUs) to sense for and exploit underutilized licensed spectrum owned by the licensed users (or primary users, PUs). Reinforcement learning (RL) is an artificial intelligence approach that enables a node to observe, learn, and make appropriate decisions on action selection in order to maximize network performance. Routing enables a source node to search for a least-cost route to its destination node. While there have been increasing efforts to enhance the traditional RL approach for routing in wireless networks, this research area remains largely unexplored in the domain of routing in CR networks. This paper applies RL in routing and investigates the effects of various features of RL (i.e., reward function, exploitation, and exploration, as well as learning rate) through simulation. New approaches and recommendations are proposed to enhance the features in order to improve the network performance brought about by RL to routing. Simulation results show that the RL parameters of the reward function, exploitation, and exploration, as well as learning rate, must be well regulated, and the new approaches proposed in this paper improves SUs' network performance without significantly jeopardizing PUs' network performance, specifically SUs' interference to PUs.

Evaluating inputs to models of hominin raw material selection: map resolution and path choices

Selection of an appropriate scale is an important decision in study design in many branches of science, since perceived patterns often change with the scales of spatial extent or resolution of an analysis. In previously published work, we created a resource selection model to determine the importance of several independent variables for the selection of lithic materials by hominins at a Middle Palaeolithic site in southern France. Two of these independent variables (calories exerted and difficulty of the terrain covered in travel from source to site) were calculated using elevation data extracted from maps. In the present paper, we examine the differences in model performance when the variables ‘Calories’ and ‘Difficulty’ are calculated using 1) three base maps for elevation that differed in map resolution (from finest to coarsest: a 1:25,000 topographic base map, SPOT DEM, and SRTM DEM), and 2) two different methods for determining the route from source to site (straight-line route and least-cost route; both methods exclude areas with slopes >60% from travel). Our best model was the one that used data calculated using the topographic base map; however, the SRTM DEM-based data produced models of essentially equal quality. Regardless of map scale, models that used data calculated using a straight-line route always outperformed models that used data calculated using a least-cost route. This supports our previous finding that a straight-line route is a more appropriate measure for the path from lithic source to site than a least-cost route. We conclude that the map resolution of each of the base maps used here is appropriate for analyses involving spatial data pertaining to Neandertal activity because this type of data is essentially always coarse-grained.

Solving the Least-Cost Route Cut and Fill Sequencing Problem Using Particle Swarm

AbstractSeveral researchers have attempted to formulate and solve different classes of the earthwork allocation problem. Linear programming (LP) and integer programming (IP) techniques have traditionally been applied to minimize transportation costs and mass-haul distances associated with earthwork processes. However, typical formulations of the earthwork allocation problem do not consider the sequence of equipment movement and are, therefore, limited in their ability to establish a practical and workable hauling plan. A more complex problem, which is formulated and solved in this research, is the least-cost route cut and fill problem (LCRCFP). The primary objective of the LCRCFP is to determine the specific route to be traveled and the quantities of soil that construction equipment must haul to meet the desired grade while minimizing the total distance traveled. In this research, the LCRCFP was formulated as a mixed binary optimization problem and solved using a traditional branch-and-bound method and a ...

How Far Out of the Way Will We Travel?

Current travel demand models are calibrated for motorized transportation and do not perform as well for nonmotorized modes. Little evidence exists on how much, and for what reasons, the routes people travel deviate from the shortest-path or least-cost routes generated by transportation models. This paper investigates differences in total distance, road type used, and built environment features for shortest-path routes versus actual routes for utilitarian bicycle trips (n = 50) and car trips (n = 67) in Metro Vancouver, Canada. Bike trips were, on average, 360 m longer than the shortest possible route; car trips were 540 m longer. Regardless of mode, people do not detour far off the shortest route: detour ratios (actual distance/shortest distance) were similar, with three-fourths of trips within 10% of the shortest distance and at least 90% within 25%. Differences in the built environment measures en route suggest why bike commuters chose to detour: the actual routes had significantly more bicycle facilities (traffic-calming features, bike stencils, and signage) than did the shortest-path routes. Compared with shortest-path routes, cyclists spent significantly less of their travel distance along arterial roads and significantly more along local roads, off-street paths, and routes with bike facilities. As expected, car trips were more likely to be along highways and less likely to be along local roads than predicted by the shortest route. The results illustrate factors that might be included in travel models to more accurately model nonmotorized transportation and provide guidance for how dense bike facilities need to be when infrastructure to support cycling is designed.

Planning Routes Across Economic Terrains: Maximizing Utility, Following Heuristics

We designed an economic task to investigate human planning of routes in landscapes where travel in different kinds of terrain incurs different costs. Participants moved their finger across a touch screen from a starting point to a destination. The screen was divided into distinct kinds of terrain and travel within each kind of terrain imposed a cost proportional to distance traveled. We varied costs and spatial configurations of terrains and participants received fixed bonuses minus the total cost of the routes they chose. We first compared performance to a model maximizing gain. All but one of 12 participants failed to adopt least-cost routes and their failure to do so reduced their winnings by about 30% (median value). We tested in detail whether participants’ choices of routes satisfied three necessary conditions (heuristics) for a route to maximize gain. We report failures of one heuristic for 7 out of 12 participants. Last of all, we modeled human performance with the assumption that participants assign subjective utilities to costs and maximize utility. For 7 out 12 participants, the fitted utility function was an accelerating power function of actual cost and for the remaining 5, a decelerating power function. We discuss connections between utility aggregation in route planning and decision under risk. Our task could be adapted to investigate human strategy and optimality of route planning in full-scale landscapes.

The sensitivity of least-cost habitat graphs to relative cost surface values

Maintaining and restoring connectivity among high-quality habitat patches is recognized as an important goal for the conservation of animal populations. To provide an efficient measure of potential connectivity pathways in heterogeneous landscapes, least-cost route analysis has been combined with graph-theoretical techniques. In this study we use spatially explicit least-cost habitat graphs to examine how matrix quality and spatial configuration influence assessments of habitat connectivity. We generated artificial landscapes comprised of three landcover types ranked consistently from low to high quality: inhospitable matrix, hospitable matrix, and habitat. We controlled the area and degree of fragmentation of each landcover in a factorial experiment for a total of 20 combinations replicated 100 times. In each landscape we compared eight sets of relative landcover qualities (cost values of 1 for habitat, between 1.5 and 150 for hospitable matrix, and 3–10,000 for inhospitable matrix). We found that the spatial location of least-cost routes was sensitive to differences in relative cost values assigned to landcover types and that the degree of sensitivity depended on the spatial structure of the landscape. Highest sensitivity was found in landscapes with fragmented habitat and between 20 and 50% hospitable matrix; sensitivity decreased as habitat fragmentation decreased and the amount of hospitable matrix increased. As a means of coping with this sensitivity, we propose identifying multiple low-cost routes between pairs of habitat patches that collectively delineate probable movement zones. These probable movement zones account for uncertainty in least-cost routes and may be more robust to variation in landcover cost values.

The vehicle routing problem in field logistics part I

The vehicle routing problem (VRP) has been characterised as one of the great success stories of operational research, providing and facilitating, for over fifty years, optimal planning solutions for vehicle fleets in a large number of real-life applications. In its simplest form, a VRP can be described as the problem of determining least-cost routes from one depot to a set of geographically dispersed “customers” (such as cities, stores, warehouses, and schools). VRP constitutes one of the most challenging combinatorial optimisation problems. A large number of different approaches have been developed over the years and a number of software packages are available on the market. In the agriculture, the VRP has only very recently been applied to the planning and execution of in-field operations, despite the fact that almost all agricultural field operations (AFO) inherently involve the motion of vehicles. In this paper, a dedicated classification of AFO is devised and tailored to a conceptual application of the VRP within the domain of agricultural field logistics. The concept regards the operations of primary agricultural machines, with the worked tracks in the field representing the “customers” using VRP methodology. By casting the agricultural fleet management problem in the framework of well-known VRP instances, over half a century of research and implementation experience can be brought to bear on the problem. This will provide for the enhanced management of conventional machinery systems, as well as, the mission and route-planning aspects of the high level control of emerging field robots.

The design of vehicle routes for a third-party logistics service provider using the simulated annealing algorithm

Increased globalisation and the subsequent competitive pressures have emphasised the importance of Third-Party Logistics (3PL) in managing logistics processes as well as customer and supplier relationships in logistics and supply chain management. Organisations can gain approximately 9% of saved costs and a 15% increase in capacity and quality, on average, through outsourcing their logistics activity to 3PL service providers. Transportation planning and management is a basic service provided by 3PL service providers with the goal to provide customer value in excess of their cost to serve customers. Since the transportation cost constitutes a significant fraction of the total logistics cost, 3PL service providers are motivated to improve their efficiency by ensuring on-time deliveries and pick-ups by designing least-cost routes with efficient routing strategies. In this paper, a Simulated Annealing (SA)-based metaheuristic algorithm was developed for and used by a 3PL service provider for the efficient routing of the vehicles for pick-up for an automotive parts manufacturing company.

Pipeline design for a least-cost router application for CO 2 transport in the CO 2 sequestration cycle

CO 2 capture and geological storage (CCS) is considered as a viable option to mitigate greenhouse gas emissions during the transition phase towards the use of clean and renewable energy. This paper concentrates on the transport of CO 2 between source (CO 2 capture at plants) and sink (geological storage reservoirs). In the cost estimation of CO 2 transport, the pipeline diameter plays an important role. In this respect, the paper reviews equations that were used in several reports on CO 2 pipeline transport. As some parameters are not taken into account in these equations, alternative formulas are proposed which calculate the proper inner diameter size based on flow rate, pressure drop per unit length, CO 2 density, CO 2 viscosity, pipeline material roughness and topographic height differences (the Darcy–Weisbach solution) and, in addition, on the amount and type of bends (the Manning solution). Comparison between calculated diameters using the reviewed and the proposed equations demonstrate the important influence of elevation difference (which is not considered in the reviewed equations) and pipeline material roughness-related factor on the calculated diameter. Concerning the latter, it is suggested that a Darcy–Weisbach roughness height of 0.045 mm better corresponds to a Manning factor of 0.009 than higher Manning values previously proposed in literature. Comparison with the actual diameter of the Weyburn pipeline confirms the accuracy of the proposed equations. Comparison with other existing CO 2 pipelines (without pressure information) indicate that the pipelines are designed for lower pressure gradients than 25 Pa/m or for (future) higher flow rates. The proposed Manning equation is implemented in an economic least-cost route planner in order to obtain the best economic solution for pipeline trajectory and corresponding diameter.

Flexible Multipath Search Algorithm for Multipurpose Location-Based Activities

An algorithm is developed that provides not only least-cost alternate routes but also ones that are close to the least-cost routes for users to select from multiple paths that route through points of interest. The algorithm utilizes a link-based search method rather than the traditional node-based search method. The link-based algorithm is able to use the existing transportation network by allowing U-turns and restricting left turns without modifications. The algorithm also uses relative prices rather than absolute prices in selecting paths. The relative price is the difference between the minimum price available in the market and the price that is available on a path. Introduction of relative prices enables the provision of flexible route guidance to meet the various needs of users. The algorithm developed has been applied to a virtual network, which successfully demonstrated the implementation of the multipath search algorithm for multipurpose activities.

AN ASP-BASED MODEL EMPLOYING A TABU SEARCH METHOD FOR MAKING e-LOGISTICS DECISIONS

In this article, a decision support system for solving the vehicle routing problem is presented. This system has been developed in a way that allows it to be used as a web-based application service provider. Therefore, it is feasible for any company to access it over the internet, in order to obtain the best fleet schedules (a set of least-cost routes) concerning its daily orders or supplies. The application consists of several web pages, written in plain Application Service Providers (ASP) and Hypertext Markup Language (HTML) code, containing the java applets and JavaScript functions that encapsulate the routing methods, and determine the routing plan.

Application of Remote Sensing and Geographic Information System in infrastructure development

Road transportation network development is a vital component of infrastructure development. Absence of database on roads of Trivandrum district was felt as a major hindrance in prioritizing improvement/development/repair of the roads for better traffic efficacy. High resolution PAN imagery (IRS-IC, September-December 1999, 1:25,000 scale) was visually interpreted to decipher road net work for preparing an elaborate database for Kerala Highway. The data were incorporated on 1:25,000 scale SOI base maps. Field verification was carried out to identify and categorize the PWD roads as per their administrative sections. Final maps were digitized in ARC/INFO environment. Information about terrain conditions was also generated using satellite remote sensing images and aerial photographs. Incorporating the height source and elevation data in the value field and taking mass points as input, a TIN (Triangulated Irregular Network) model of a sample area near Vellanad, 22 km east of Trivandrum city was created to analyse the terrain-road network interrelationship. Our case study involving draping of road network on TIN model as well as on geomorphology map established that this methodology could be used to define alternative and efficient route corridors, with particular emphasis on selection of the least-cost route and prioritization of repair.

C02 Emission Reduction in Canada: Results from an Energy System Model

Canada is committed to stabilizing emissions of greenhouse gases at 1990 levels by the year 2000. This paper examines the costs and benefits of meeting the key component of this commitment: energy-related carbon dioxide (CO2) emissions. The analysis uses a dynamic linear programming methodology to produce a process-oriented, techno-economic model of the Canadian energy system for the period 1990-2030. Three scenarios are analyzed to investigate the effects of sectoral vs. overall limits on C02 emissions compared to a business-as-usual (BAU) base case. The results from this work point to least-cost routes to CO2 emission reduction, as well as addressing the issue of equity vs. efficiency in achieving the reductions. Potential collateral benefits to emission reduction are also discussed.

A spatiotemporal analysis for fed beef in the southeastern United States

The southeastern states of Mississippi, Alabama, Georgia, and Florida currently export the majority of their feeder calves and import processed fed beef to satisfy consumer demand. The objective of this article is to determine the least-cost routes of backgrounding, feeding/finishing, slaughtering/processing, and distributing boxed beef for these southeastern states. A spatiotemporal model is developed which determines the optimal routes for all production, processing, and distribution phases. Results indicate that the least-cost solution could be reached by substantially expanding production, in all phases, in southern Alabama.

Planning Time-Phased Regional Treatment Systems

An economic optimization model for selecting least-cost regional wastewater treatment facility locations, interceptor routes, and capacity expansion schedules is developed. The model explicitly considers the interaction between facility location and capacity expansion decisions on total system cost. Cost functions for treatment facilities and interceptors and growth patterns for future wastewater flows may be of any form. The model is solved with a three-phase heuristic procedure that makes strong use of dynamic programming. In comparison with a mixed integer programming model on a large-scale problem the procedure demonstrates significant advantages in computational time, accuracy, and user requirements. The model is applied to facilities planning in a 208 study area of Massachusetts to demonstrate how the economic impacts of alternative management objectives and demographic projections can be assessed.