CN101833699A - Heuristic route segment path-finding method for ship route design - Google Patents
Heuristic route segment path-finding method for ship route design Download PDFInfo
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Abstract
The invention discloses a heuristic route segment path-finding method for ship route design, comprising heuristic search, a heuristic shortest route segment path-finding algorithm analysis method, an A* algorithm heuristic principle and an improved shortest path algorithm, wherein the heuristic route segment path-finding algorithm puts forwards a method establishing a navigable path tree to reduce meaningless path searching time by being based on a point to point navigable line algorithm and combining with the A* algorithm heuristic principle. By analyzing the particularity of the route segment path-finding algorithm based on a vector diagram in the ship route design, the route segment path-finding algorithm is improved according to an analysis result, the accuracy of a generated route segment path is enhanced and the path-finding efficiency is further increased. Lands, islands and other barriers positioned on a map of the world are expressed by polygons in the vector diagram, and route segment path-finding is to finally find an optimal route segment from communicated paths which are generated between the two outer points of the polygons without passing through the polygons.
Description
Technical field
The present invention relates to the naval technology field, relate in particular to a kind of heuristic leg path-finding method that is used for the steamer line design.
Background technology
In shipping, the quality of flight-line design has great influence to improving the shipping economic benefit.For this reason, it is vital designing a desirable course line.Flight-line design is a more complicated and elaboration, relates to and having a wide range of knowlege, and selectivity and polytrope are strong.Boats and ships ride the sea, and travel along route with land automobile and train and make a world of difference.Because the sea area is wide, move place is big, meteorological condition is changeable, various boats and ships situation difference differences select the course line also to become very complicated.Because flight-line design Air China phase library is the basis, sets up Worldwide Shipping course line transportation network framework by the storehouse, leg.So seeking the footpath, the leg just becomes the emphasis of flight-line design, but the shortest shipping communication path of point-to-point transmission search at sea, and this is that map in the flight-line design is sought the footpath problem.
At artificial intelligence field, the procedural representation that the footpath is sought in the leg is: be starting point by initial data base (state), constantly use and seek the footpath rule in current database (state), change database (state) until the search procedure that comprises impact point.Carrying out the leg and seek the footpath in the world map marine site, is to search in implicit expression figure, and the size of search volume affects to a great extent seeks footpath efficient.World's nautical route design at present is based on the flight-line design of world map, the map fineness is big and figure is complicated, if adopt grating map will face following problem: 1, map rasterizing problem, during the rasterizing of same ratio, ratio is big, can not express the connection in narrow basins such as canal, navigation channel; Ratio is little, and the network behind the rasterizing is huge, has a strong impact on search speed.For meticulous expression straitly just as the time do not make grid network too huge, need adopt different rasterizing ratios in different waters, increased data structure and algorithm complex like this.2, connective pre-service, but grid need be judged the general character of grid when searching for, and the needs consideration is various can understanding and considerate shape.Efficient when seeking footpath algorithm operation in order not influence, but need carry out the pre-service of the grid general character.But in dynamic map, but the general character of grid needs to upgrade.3, expression precision, the expression precision of grating map is by the decision of rasterizing ratio, and generally a ceramic tile is a minimum unit in online game.Therefore, if allow the recreation in the object course be not frank and outspoken, just need carry out the path smoothing processing.
Summary of the invention
Technical matters to be solved by this invention is to have analyzed the drawback that grating map exists in flight-line design, proposes to carry out flight-line design based on polar plot and can avoid these deficiencies.The present invention mainly designs heuristic leg and seeks the footpath algorithm, but this algorithm is based on point-to-point transmission shipping line algorithm, in conjunction with A
*The heuristic principle of algorithm, but the method that has proposed foundation shipping path tree is to reduce the search time in meaningless path.Then, analyzed based on the leg of polar plot and sought the singularity of footpath algorithm in steamer line design.According to analysis result the footpath algorithm is sought in the leg and improve, the accuracy that has improved the path, leg that generates reaches further to have improved seeks footpath efficient.The land of world map, island and other barriers represented by polygon in polar plot, and the leg is sought the footpath and is polygon outside the point-to-point transmission generation and do not pass through polygonal communication path, finally finds optimum leg.
Described method comprises heuristic search, is expanded by selecting most promising node, improves search efficiency, by detecting to determine reasonably order.
Described method comprises that the shortest heuristic leg seeks footpath Algorithm Analysis method, and search P1 is a shortest path between terminal point for starting point P2, but creates the shipping path tree.
Described method comprises A
*The heuristic principle of algorithm, A
*Algorithm is a kind of ordered search algorithm, and its characteristics are in the definition to evaluation function, but algorithm is based on point-to-point transmission shipping line algorithm, in conjunction with A
*The heuristic principle of algorithm, but the method for foundation shipping path tree.
Described method comprises improved shortest path first, and P1 is that starting point, P2 are improved shortest path first between terminal point.
Description of drawings
Fig. 1 is that the present invention adopts the synoptic diagram that concerns between the searching algorithm;
Fig. 2 is an algorithm condition for consistence synoptic diagram of the present invention;
Fig. 3 is that single body of the present invention is sought footpath algorithm exemplary plot;
Fig. 4 is the generating algorithm exemplary plot of the present invention around the barrier route;
But Fig. 5 is a point-to-point transmission shipping line synoptic diagram of the present invention;
But Fig. 6 is the present invention's shipping tree synoptic diagram;
Fig. 7 is that impact point of the present invention is surrounded synoptic diagram by land;
Fig. 8 is that the present invention centers on barrier route selection synoptic diagram;
But Fig. 9 is the present invention's shipping path tree class figure.
Embodiment
In order to make those skilled in the art person understand scheme of the invention process better, the invention process is described in further detail below in conjunction with drawings and embodiments.
At first, be that the present invention adopts the synoptic diagram that concerns between the searching algorithm with reference to Fig. 1:
The information in problem itself and the search procedure is not all used in depth-first search and breadth-first search, and search is carrying out according to permanent order of blindness fully.The efficient of blind search is low, expends too much computer memory and time.If can find a kind of method to be used to arrange the order for the treatment of expanding node, promptly select most promising node to be expanded, so, search efficiency will improve greatly.In many cases, can claim this class search to be heuristic search (Heuristically Search) or information search (Informed Search) is arranged by detecting the next reasonably order of determining.
Heuristic search is that the heuristic information that utilizes problem to have comes guiding search, reaches to reduce the hunting zone, reduces the purpose of problem complexity, and this search procedure of heuristic information of utilizing all is called heuristic search.
In the heuristic search process, sort to OPEN table, this just needs a kind of method and calculates and treat that expanding node is hopeful to lead to destination node in various degree, always wishes to find the expanding node for the treatment of that is hopeful to lead to destination node most preferentially to expand.A kind of the most frequently used method is that an evaluation function f of definition (Evaluation Function) calculates each node, and its purpose is used for estimating the node of " being hopeful " exactly.The principle of a common reference of evaluation function of definition has: node is in the probability on the optimal path; Obtain distance metric or difference measurement between any one node and the destination node collection; Characteristics according to general layout (problem of game) or state are given a mark.Promptly, provide the method for calculating evaluation function from probability angle, difference angle or scoring method according to the heuristic information of problem.
The task of evaluation function is exactly to estimate the significance level of node to be searched, gives their prioritized.Evaluation function f (n) can be any one function, as to define it be that node n is in the probability on the optimal path, or the distance between n node and the destination node, or the score of n general layout or the like.In general, estimate the value of a node, must take all factors into consideration the factor of two aspects: cost of having paid and the cost that will pay.At this, we are defined as evaluation function f (n) the cost estimated value that arrives the minimal cost path of destination node from start node through the n node.Its general type is:
f(n)＝g(n)+h(n)
Wherein g (n) is the actual cost from start node to the n node, and h (n) is the estimation cost of the optimal path from the n node to destination node, mainly is the heuristic information that h (n) has embodied search.Because actual cost g (n) can come out according to the search tree actual computation that generates, and estimate that cost h (n) depends on certain experience estimation, it derives from our understanding to some characteristic of separating of problem, and these characteristics can help us to find separating of problem quickly.
In the evaluation function, g and h relative scale can be controlled by the size of selecting w among the f=g+w*h.W is a positive number, and very big w value then can over emphasis inspire component, and too small w value is the feature of outstanding breadth-first then.Empirical evidence makes the w value with the variation that is inversely proportional to of the node degree of depth in the search tree, can improve search efficiency.Promptly in the place of depth as shallow, the main dependence of search inspired component; And darker place, search becomes breadth-first gradually, and is finally found with a certain paths that guarantees the arrival target.
Ordered search algorithm is arranged GRAPHSEARCH step h with evaluation function f) in node on the OPEN table.According to custom, the node on the OPEN table is arranged according to the incremental order of their f functional values.By inference, certain node with low assessment values may be on the optimal path.Use certain algorithm (as etc. the cost algorithm) select to have on the OPEN table node that the node of minimum f value will be expanded as the next one.This searching method is called ordered search or best-first search, and its algorithm is called ordered search algorithm or best priority algorithm.As seen it always selects the node that most promising node will be expanded as the next one.
Ordered search (Ordered Search) is called best first search (Best-First Search) again.
Order state space search algorithm is as follows:
A) start node S is put in the OPEN table, calculates f (S) and its value and node S are connected.
B) if OPEN is an empty table, then failure is withdrawed from, and nothing is separated.
C) from the OPEN table, select the minimum node i of a f value.The result has several nodes qualified, when wherein having one when the destination node, then selects this destination node, otherwise just selects wherein any node as node i.
D) node i is shifted out from the OPEN table, and it is put into the expanding node table of CLOSED.
E) if i is a destination node, then successfully withdraw from, try to achieve one and separate.
F) expanding node i generates its whole descendant nodes.Each descendant node j for i:
I) calculate f (j).
If ii) j neither in the OPEN table, not in the CLOSED table, then inserts the OPEN table to it with evaluation function f again.Add a pointer that points to its former generation's node i from j, so that in case remember a solution path when finding destination node.
If iii) j is on the OPEN table or on the CLOSED table, the f value of this node in table crossed of f value of more just j having been calculated and previous calculations then.If new f value is less, then:
1. replace old value with this new value.
2. point to i from j, rather than point to its former generation's node.
If 3. node j is in the CLOSED table, then it is retracted the OPEN table.
G) turn to step b).
Breadth-first search, etc. cost search and depth-first search completely are special cases of ordered search technology.For breadth-first search, f (i) is the degree of depth of node i.For etc. cost search, f (i) is the cost from start node to this section of node i path.
The validity of ordered search directly depends on the selection of f, if the f that selects is improper, ordered search just may lose best separating even whole separating.If the hope accurately that is suitable for is not measured, the selection of f will be referred to the content of two aspects so: be the compromise proposal between time and the space on the one hand; Be to guarantee to have separating or separating arbitrarily of an optimum on the other hand.
A
*Algorithm is an ancient technology, and it is used to solve all kinds of mathematical problems at first.The artificial intelligence study early stage it be used to solve the pathfinding problem.Pathfinding algorithm at present commonly used is A
*Mode, principle are to obtain by the node that continuous search approaches the destination.A
*Search method is a kind of optimized method for searching, be current usefulness at most also be state-of-the-art algorithm, its speed is very fast on fairly simple map, can find shortest path very soon, and uses
*The A algorithm can be controlled the search scale easily and stop up to prevent program.
√ A
*The evaluation function of algorithm
Describe graph search (GRAPHSEARCH) in detail with optimal searching algorithm.Optimal searching algorithm is according to the added value of function, and (in graph search step h) resets the node among the OPEN, as eight digital problems.This algorithm of GRAPHSEARCH is called A
*Algorithm.Definition makes A
*The function of carrying out the search of breadth first search or identical cost is feasible.For the family of functions that determines to use, must introduce some other symbols earlier.
If the actual cost of the minimal cost path h (n)=node n and the destination node (traveling through all possible destination node and all possible paths) from n to them.
If the cost of the minimal cost path of g (n)=from start node s to node n.
F (n)=g (n)+h (n) is exactly from s to the destination node and the cost of the minimal cost path of process node n so.
To each node n, establish h
*(n) (the inspiration factor) is certain estimation of h (n), g
*(n) (depth factor) is by A
*The cost of the minimal cost path of finding that arrives node n.At algorithm A
*In, evaluation function f
*Be the estimation of f, this estimation can be provided by following formula:
f
*(n)=g
*(n)+h
*(n) formula (2-3)
For g (n), one significantly select be exactly in the search tree from s to n the cost in this section path, this cost can be when seeking pointer from n to s, the cost of each section camber line that is run into is added up provides (this paths is exactly the minimal cost path from s to n that up to the present finds with searching algorithm).This definition has comprised g
*(n) 〉=g (n).Estimation h for h (n)
*(n), it depends on the heuristic information in the field of relevant issues, claims h
*Be evaluation function.
A
*Algorithm is a kind of ordered search algorithm, and its characteristics are in the definition to evaluation function.For general ordered search, always select the minimum node of f value as expanding node.Therefore, f finds the viewpoint of a minimal cost path to estimate node as required, so the evaluation function value that can consider each node n is two components: cost from start node to node n and the cost that arrives destination node from node n.
√ A
*Algorithm
A
*Algorithm:
A) generate one and only comprise start node s, search graph G, s is placed in the tabulation of being OPEN.
B) generate a tabulation CLOSED, it be initialized as sky.
C) if OPEN is empty, then failure is withdrawed from.
D) first node of selection OPEN moves into CLOSED to it from OPEN, claims that this node is n0.
E) if n is a destination node, in G, the pointer from n to s finds a paths, and the scheme that achieves a solution successfully withdraws from (this pointer definition a search tree, set up in step g).
F) expanding node n generates its follow-up set of node M, and in G, the ancestors of n can not be in M.The member who settles in G makes them become the follow-up of n.
G) from M each not the member among G set up a pointer (for example, neither in OPEN, also not in CLOSED) that points to n.These members of M are added among the OPEN.Each member m in OPEN or among the CLOSED to M, if the best path of the arrival m that up to the present finds is passed through n, just its pointed n. to each member of the M in CLOSED, it is follow-up to be redirected its each in G, so that they point to their ancestors along the best path of up to the present finding.
H) by increasing progressively f
*Value is reset OPEN (identical minimum f
*Value can solve according to the darkest node in the search tree).
I) return step c).
In step g),, will be redirected the pointer that points to this node if search procedure finds that the cost of a node of paths arrival is lower than existing path cost.The redirected Search Results of preserving the back of the node descendants in CLOSED still may need exponential calculation cost.Therefore, in step g), usually can not realize.Along with pushing ahead of search, wherein some pointer finally will be redirected.
A
*Algorithm statement itself is got up very simple, and key is on code optimization, and basic thinking generally all is to exchange the time (search speed) for space (being taking of internal memory), also has such as pretreated technology of some maps such as the multistage accuracies of map in addition.
√ A
*Receivability
To figure and h
*Apply the A that some conditions can guarantee to be applied to figure
*Algorithm can find minimal cost path.The condition of figure is:
● if each node has descendant node among the figure, and number is limited;
● the cost of all arcs is all greater than certain positive number among the figure.
h
*Condition be:
To all the node n in the search graph, h
*(n)≤and h (n), h
*Can not surpass the estimation of actual value h, such h
*Function is called as the optimization estimator.
With these three constraint conditions, as long as have the path that arrives target, A
*Algorithm just can guarantee to find the optimal path of an arrival target.
If A
*Two version A
1 *And A
2 *, its difference is all non-destination nodes, h
1＜h
2, so just say A
1 *Compare A
2 *More well-informed (informed).
The relation of having summarized above-mentioned some searching algorithms of having discussed.When to all node h
*During ≡ 0, what obtain is identical cost algorithms (search is outwards expanded along the edge of identical cost).Work as f
*(n)=g
*(n)=and during the degree of depth (n), what obtain is breadth-first search algorithm, it is outwards expanded along the edge of same depth.Identical cost and breadth-first algorithm all are A
*(h
*≡ 0) special circumstances, so they also all are admissible.
With reference to Fig. 2 is algorithm condition for consistence synoptic diagram of the present invention:
Consider a pair of node (n
i, n
j), n
jBe n
iOne follow-up.If this nodes all in search graph are to all satisfying following condition:
h
*(n
i)-h
*(n
j)≤C (n
i, n
j), wherein.C (n
i, n
j) moving be from n
iTo n
jCost.
Following formula is also write: h
*(n
i)≤C (n
i, n
j)+h
*(n
j) and h
*(n
j) 〉=h
*(n
i)-C (n
i, n
j)
Just say that h obeys condition for consistence.This conditional statement any paths in search graph, the minimizing of appraisal that arrives the optimum cost of target can be greater than this path arc cost.That is to say that after the known cost of having considered an arc, heuristic function is consistent in the part.When the consistance function had hinted that value when node in the search tree is away from start node, it was dull non-decreasing.If n
iAnd n
jBe by A
*Two nodes that on search tree, produce, n
jBe n
iFollow-up.If satisfy condition for consistence, f (n is just arranged
j) 〉=f (n
i).In order to prove this fact, can be from condition for consistence:
h
*(n
j) 〉=h
*(n
i)-C (n
i, n
j) formula (2-4)
All add g for the following formula both sides
*(n
j) have:
h
*(n
j)+g
*(n
j) 〉=h
*(n
i)+g
*(n
j)-C (n
i, n
j) formula (2-5)
But g
*(n
j)=g
*(n
i)+C (n
i, n
j) formula (2-6)
Therefore, f
*(n
j) 〉=f
*(n
i) formula (2-7)
For this reason, condition for consistence is (to h
*) often be called as monotony condition (to f
*).
Condition for consistence is very important, because when it is satisfied, and A
*No longer need to be redirected pointer, searching for a figure and search tree does not just have any difference.
A lot of heuristic functions satisfy condition for consistence.For example, " the out of position digital number " function in the eight digital problems is exactly an example.When a heuristic function does not satisfy condition for consistence, but others are adjusted this function at searching period so and are made it satisfy condition for consistence when being the acceptable condition.If, at A
*Each step, check the follow-up h of the node n just expanded
*Value.Any h value is less than h
*(n) node of value deducts arc cost from n to this node and will obtain their adjusted h
*Value, they just just equal h like this
*(n) value deducts the income value of that section arc cost.
With reference to Fig. 3 is that single body of the present invention is sought footpath algorithm exemplary plot:
The basic problem that single body seeks that the footpath needs in the algorithm to solve is an avoiding obstacles, and the method for easy realization is:
A) draw straight line A from origin-to-destination.
B) advance towards terminal point along line A, once running into barrier in the direction of the clock around the barrier walking, until meeting straight line A.
C) repeating step b), just one finally arrive the destination surely.
D) this algorithm computation path of coming out not is the shortest, sometimes also can walk out strange route, but speed is very fast, can satisfy real-time requirement in the recreation on more low-grade PC, in the recreation " red police " to seek the footpath algorithm be based on this.Can do some to above-mentioned algorithm and improve, make the track route of loose impediment more become reasonable.
Loose impediment is obstacle thing walking in the counterclockwise direction, and should not go in the direction of the clock to talk in a roundabout way.So, when running into barrier, at first to judge around direction.If compared with clockwise direction, walking counterclockwise can be met straight line A with shorter path, chooses so counterclockwise and walks around barrier, and vice versa.
The distance that detours is reduced in the path that as far as possible takes the air line.Earlier go out track route B by above-mentioned algorithm computation, then when loose impediment is advanced around barrier on route B, whenever make a move and just draw straight line C to terminal point from current location, if along straight line C advance can with at present also not certain section of the track route B of process meet, just stop detouring, directly walk to route B, thereby shortened the path by straight line C.
When terminal point is among barrier surrounds, loose impediment may be reached home never, is in the direction of the clock or counterclockwise detours and all can only retour, and can't advance.Processing mode for this situation is exactly one week of obstacle thing, selects from the nearest place of terminal point as terminal point.
Single body seeks that the footpath algorithm is mainly concerned with straight line in specific implementation and around the generation technique of barrier route.The rasterisation of straight line generates can reference computers graphics teaching material, repeats no more here.Provide generating algorithm (being example in a clockwise direction) below around the barrier route:
A) when walking around barrier, to judge the direction of current barrier earlier with respect to loose impediment, be labeled as integer i.For example: barrier is in the front-right of loose impediment, and just note is made direction 5.
B) then direction j=(i+n) mod8 is checked in loose impediment successively, (n=1...7), and till finding direction j place clear.If barrier be positioned at directly over 7, loose impediment sees that at first can the upper left side pass through to 0=(7+1) mod8, if obstructed left direction 1=(7+2) mod8 that just then tries, also not all right go up by figure successively again shown in arrow sound out all the other several directions, until finding an exit, and make a move toward this direction row.If barrier is positioned at lower left 2, then check by seven directions such as below 3, lower right 4, right-hand 5, upper right side 6, top 7, upper left side 0, lefts 1 whether path is arranged successively.As for the processing of barrier, draw analogous conclusions with respect to other position of loose impediment.
C) repeating step a), b), just can finish clockwise and walk around barrier.
But with reference to Fig. 5 is point-to-point transmission shipping line synoptic diagram of the present invention:
But set up the shipping line of P1, P2 point-to-point transmission according to following steps, P1 is starting point S, and P2 is terminal point E, Path[] for turning to the group of counting in the path, leg:
(1) tie point S, E, line SE are the shipping p-wire;
(2) if line SE does not intersect (promptly not passing through land, barrier etc.) with any polygon, but then line SE is the shipping line of point-to-point transmission, to (5) step; Otherwise P1P2 and polygon intersect, to (3) step;
(3) zequin S is to intersecting with p-wire and (two, but be called the shipping point) A1, A2 apart from the nearest polygonal point of contact of starting point;
(4) be new terminal point with the A1 point, forward step (1) to but search starting point S is the shipping line of terminal point E to A1;
(5) E is added Path[].Work as E=P2, but find the shipping line of P1 to P2, Path[] be the turning point sequence in path, leg; As E ≠ P2, forwarding step (1) search E to is starting point S, but P2 is the shipping line of terminal point E.
But according to above shipping line search method, a but shipping line between search P1, P2.
2) the footpath algorithm is sought in the shortest leg of point-to-point transmission
The simplest, but on search point-to-point transmission shipping line basis, when running into barrier, but remember the shipping point, but but search for the shipping line respectively from shipping point, but search out all shipping paths like this, path (1), (2), (3) can obtain at 2 and ask shortest path, and (2) are shortest path.
Above method will travel through all feasible paths, adopt depth-first strategy, inefficiency.Following surface analysis also designs the shortest heuristic leg and seeks the footpath algorithm.
The footpath Algorithm Analysis is sought in the shortest heuristic leg:
But based on point-to-point transmission shipping line algorithm, determine the route searching direction, reduce the blind search route, dwindle the search volume, improve search speed.
But when selecting next one shipping point, adopt the evaluation function control strategy.But select optimum current next step shipping point search of shipping point beginning according to evaluation function.
But the heuristic evaluation function of shipping point n:
f(n)＝g(n)+h(n)
Wherein, g (n) but be distance from starting point to shipping point n, h (n) but be the air line distance of shipping point n to impact point.
But shipping path tree
Every but all may there be many shipping lines in the leg, finally only selects the shipping line of an optimum.In order to save search time, the non-optimal path that stops search as soon as possible seems very necessary.But adopt the shipping path tree method of (being equivalent to the CLOSED table in the graph-search strategy), in the route searching process of leg, set up starting point to impact point searching route tree, but shipping point is node in the tree.But, write down current shortest path PathLen if search the shipping line.But search the relatively relation of g (n) and PathLen of new shipping point n, if g (n) 〉=PathLen then mark stop further to search for from n at every turn.
P1 is that starting point, P2 are that shortest path first is as follows between terminal point E:
Initial shortest path length PathLen is ∞; But OPEN table is arranged according to evaluation function value ascending order and is tabulated for current shipping point node in the path tree (mark stop search except) pointer; But n is current shipping point.
(1) but P1 is shipping path tree root node Root, Root is current Parent node, makes n=P1;
(2) calculate f (n), the n node pointer is inserted the OPEN table in proper order;
(3) shift out p from OPEN heading end, but p correspondence shipping point is starting point S;
(4) connect S, E, line SE is the shipping p-wire;
(5) if line SE does not intersect (promptly not passing through land, barrier etc.) with any polygon, but then line SE is the shipping line of point-to-point transmission, to (8) step; Otherwise, to (6) step;
(6) zequin S is to intersecting with p-wire and (two get final product the shipping point) TP1, TP2 apart from the nearest polygonal point of contact of starting point;
(7) but be new terminal point with first shipping point TP1, forward step (4) to but search starting point S is the shipping line of terminal point E to TP1; But with second shipping point TP2 is new terminal point, forward step (4) to but search starting point S is the shipping line of terminal point E to TP2;
(8) but be the present invention's shipping tree synoptic diagram with reference to Fig. 6:
Work as E==P2, but find the shipping line of P1 to P2.
A) create leaf node with P2, make the child node of current parent's node Parent;
B) calculating the new route distance is currPathLen;
C) upgrade shortest path length (PathLen=(PathLen==∞) currPathLen:Min (PathLen, currPathLen)) in the present tree.
As E ≠ P2,
A) create new node with E, add under current parent's node Parent as its child node;
B) calculate present node evaluation function f (E);
C) if f (E) 〉=PathLen, mark stops to change step (3) from present node search;
D) the present node pointer inserts the OPEN table according to f (E) order;
E) the new node conduct is current parent's node Parent;
F) forwarding step (4) search E to is starting point S, but P2 is the shipping line of terminal point E.
(9) path of the leaf node of shortest path length PathLen correspondence (leaf node dates back to the reverse path of root node) is the path, the shortest leg of point-to-point transmission.
Adopt above algorithm, P1 is to the shortest path between P2 in search, but creates the shipping path tree.Wherein path (3) have surpassed shortest path owing to f (d) and have stopped search at the d place.
Seeking the footpath based on the leg of polar plot is to seek the footpath algorithm in the special applications in navigation field, has its singularity, be that impact point of the present invention is surrounded synoptic diagram by land with reference to Fig. 7, has analyzed the leg and has sought special circumstances in the algorithm of footpath:
1) the shipping p-wire is chosen problem
When choosing the shipping p-wire of point-to-point transmission, directly connect 2 points.The earth is a continuous sphere, and therefore, what this mode was chosen in flight-line design is not optimum p-wire.
We change shipping p-wire choosing method, and adopting the great circle line of point-to-point transmission is the shipping p-wire, and we represent circular arc with broken line in the plane, and the shipping p-wire is represented by straight-line segment string (one group of end to end non-closed line segment) like this.
2) course line path deviation target problem
But when generating point-to-point transmission shipping line, when impact point is surrounded by land, begin searching route from P1 and will depart from P2, but and can't find the shipping line.
From the P1 beginning, when toward (1) direction search, departed from objectives; When toward (2) direction search, but through behind the shipping point A, A still can not sail through to P2, so but look for next one shipping point from the A point, calculate the A point with respect to polygonal point of contact.Wherein the C point exists and repeats (1) routing problem toward (1) direction; But another one shipping point B's P2, this point have departed from objectives, and can't find the shipping line of P1 to P2 forever but should be.
In order to solve when point during by the polygon semi-surrounding, the problem that searching route departs from objectives, but we propose some the strategy that the computing method at polygonal local point of contact are chosen shipping point.When but next one shipping point departs from objectives, calculate shipping point strategy but change.According to the method, behind the A point, searching route changes (3) into, but has finally found the shipping line of P1 to P2.
3) repeat search routing problem
With reference to Fig. 8 is that the present invention centers on barrier route selection synoptic diagram, 2) but in when having pointed out search shipping line, have path repeat search problem.Exist this problem reason to be, but search during shipping point, and carrying out along certain fixed-direction, but but when finding two shippings, direction wherein is " review " path of having searched for just at every turn.
In order to solve the duplicate paths problem, but when search shipping point,, avoid " review " to search for according to fixing direction search (clockwise or counterclockwise).Note simultaneously, this method be around same polygon search the time according to fixed-direction, but this direction is determined by the shipping point that begins around current polygon search.Therefore, but when jumping to another one polygon search shipping line from certain polygon, this direction may change.Search for point along clockwise direction from P1, need jump to the another one polygon, but have two shipping point B and C, but when continuing search shipping line through B, search for along clockwise direction (1) through A; But when continuing search shipping line through C, search for along counter clockwise direction (2).
But, adapt to flight-line design is calculated shortest path at sphere singularity by using great circle route instead as the p-wire in the shipping line algorithm; But in shipping line search process, increase the direction of search factor,, prevent " review " search to guarantee when same barrier is searched for, keeping the direction of search; But during search next one shipping point, the detection that departs from objectives prevents to arrive impact point.
1) but improved shipping line algorithm
The shipping p-wire adopts the great circle line that but former shipping line search algorithm is improved.But set up the shipping line of P1, P2 point-to-point transmission, P1 is starting point S, and P2 is terminal point E, Path[] but be the array of shipping great circle line in the path, leg, and initial search direction is clockwise and counterclockwise both direction:
(1) great circle line SE is order line segment aggregate Array[between S, E], Array[] as the shipping p-wire;
(2) order travels through Array[] judge whether line segment intersects with polygon, if great circle line SE does not intersect (promptly not passing through land, barrier etc.) with any polygon, but then great circle line SE is the shipping line of point-to-point transmission, to (5) step; Otherwise, to (3) step;
(3), adopt point to polygon point of contact strategy, but zequin S is to intersecting with p-wire and apart from the nearest polygonal shipping point of starting point according to the direction of search.
A) two-way, but a shipping point respectively searched for towards clockwise, counter clockwise direction respectively;
B) clockwise, but a shipping point searched for toward the clockwise direction;
C) counterclockwise, but towards counterclockwise searching for a shipping point.
Judge but whether each shipping point departs from objectives.If depart from objectives, but, adopt point, but but calculate and replace the replacement shipping point of current shipping point to the local point of contact of polygon strategy according to this shipping point direction.
(4) but be new terminal point E with shipping point, forward step (1) to but search starting point S to the shipping line of terminal point E;
(5) with great circle line SE strings of segments Array[] adding Path[].Work as E=P2, but find the shipping line of P1 to P2, Path[] middle conductor string end points generic sequence is the turning point sequence in path, leg; As E ≠ P2, forwarding step (1) search E to is starting point S, but P2 is the shipping line of terminal point E.
2) improved shortest path first
But according to the improvement of shipping p-wire, but the heuristic evaluation function of shipping point n is amended as follows:
f(n)＝g(n)+h(n)
Wherein, g (n) but be distance from starting point to shipping point n, h (n) but be the great circle linear distance of shipping point n to impact point.
P1 is that starting point, P2 are that improved shortest path first is as follows between terminal point E:
Initial shortest path length PathLen is ∞; But OPEN table is arranged tabulation for current shipping node in the path tree (mark stop search except) pointer according to evaluation function value ascending order; But n is current shipping node.
(1) but be shipping path tree root node Root with P1, Root is current Parent node, initial search direction is two-way, makes n=P1;
(2) calculate f (n), the n node pointer is inserted the OPEN table in proper order;
(3) shift out p from OPEN heading end, but p correspondence shipping point is starting point S;
(4) great circle line SE is order line segment aggregate Array[between connection S, E], Array[] as the shipping p-wire;
(5) order travels through Array[] judge whether line segment intersects with polygon, if great circle line SE does not intersect (promptly not passing through land, barrier etc.) with any polygon, but then great circle line SE is the shipping line of point-to-point transmission, to (8) step; Otherwise, to (6) step;
(6), adopt point to polygon point of contact strategy, but zequin S and write down the corresponding direction of search to intersecting with p-wire and apart from the nearest polygonal shipping point of starting point according to the direction of search.
D) two-way, but a shipping point respectively searched for towards clockwise, counter clockwise direction respectively;
E) clockwise, but a shipping point searched for toward the clockwise direction;
F) counterclockwise, but towards counterclockwise searching for a shipping point.
Judge but whether each shipping point departs from objectives.If depart from objectives, but, adopt point, but but calculate and replace the replacement shipping point of current shipping point to the local point of contact of polygon strategy according to this shipping point direction.
(7) but be new terminal point with shipping point TP respectively, according to (2), (3), (4), (5) but recursive calculation starting point S is the shipping line of terminal point E to TP, the direction of search is the corresponding direction of search of TP;
(8) with Array[] create new node, add under current parent's node Parent as its child node.
Work as E==P2, but find the shipping line of P1 to P2,
A) create leaf node with P2, as the child node of new node;
B) calculating the new route distance is currPathLen;
C) upgrade shortest path length (PathLen=(PathLen==∞) in the present tree
currPathLen：Min(PathLen，currPathLen))。
As E ≠ P2,
A) calculate present node evaluation function f (E);
B) if f (E) 〉=PathLen, mark stops to change step (3) from present node search;
C) the present node pointer inserts the OPEN table according to f (E) order;
D) new node is current parent's node Parent;
E) changeing step (4) search E is starting point S, but P2 is the shipping line of terminal point E, the direction of search be the E counterparty to.
(9) path of the leaf node of shortest path length PathLen correspondence (leaf node dates back to the reverse path of root node) is the path, the shortest leg of point-to-point transmission.
But with reference to Fig. 9 is the present invention's shipping path tree class figure:
Root node is the leg starting point, and leaf node is the leg terminal point, and tree node primitive data nodeData is the set of IShape2D type, and each node is by NodeDataIdx key map metadata.Leg computation process is the process that makes up the leg path tree, and all leaf nodes of visit after the tree establishment is finished, the pel of the RouteMap index of leaf node are linked in sequence and just are the path, leg.
Interface is calculated in the leg:
Public void CalculateRoute (LineString2D testline, RouteTree tree, RouteTreeNodeparent, Polygon2D.TANGENTPOINT_SEARCH_DIRECT factor); // calculate the path, leg of p-wire testline, build path tree tree, the leading portion road of current p-wire only node is parent, current searching direction is factor.
More than the invention process is described in detail, used embodiment herein the present invention set forth, more than the explanation of Shi Shiing just is used for help understanding method of the present invention; Simultaneously, for one of ordinary skill in the art, according to thought of the present invention, the part that all can change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.
Claims (9)
1. one kind is used for the heuristic leg path-finding method that steamer line designs, and it is characterized in that described method comprises: footpath Algorithm Analysis method, A are sought in heuristic search, the shortest heuristic leg
*The heuristic principle of algorithm, the method for solution repeat search routing problem, but improved shipping line algorithm and improved shortest path first.
2. method according to claim 1 is characterized in that, described heuristic search is expanded by selecting most promising node, improves search efficiency, by detecting to determine reasonably order.
3. method according to claim 1 is characterized in that, footpath Algorithm Analysis method is sought in described the shortest heuristic leg, and search P1 is a shortest path between terminal point for starting point P2, but creates the shipping path tree.
4. method according to claim 1 is characterized in that, described A
*The heuristic principle of algorithm, A
*Algorithm is a kind of ordered search algorithm, and its characteristics are in the definition to evaluation function, but algorithm based on point-to-point transmission shipping line algorithm, but set up the method for shipping path tree.
5. method according to claim 1, it is characterized in that, the method of described solution repeat search routing problem, but by using great circle route instead as the p-wire in the shipping line algorithm, adapt to flight-line design and calculate the singularity of shortest path at sphere, but in shipping line search process, increase the direction of search factor, to guarantee when same barrier is searched for, the keeping direction of search, prevent " review " search, but during search next one shipping point, the detection that departs from objectives prevents to arrive impact point.
6. method according to claim 1 is characterized in that, but described improved shipping line algorithm, but the shipping p-wire adopts the great circle line that former shipping line search algorithm is improved.
7. method according to claim 1 is characterized in that, described improved shortest path first, P1 are that starting point, P2 are that improved shortest path first comprises between terminal point E:
Initial shortest path length PathLen is ∞; But OPEN table is arranged tabulation for current shipping node in the path tree (mark stop search except) pointer according to evaluation function value ascending order; But n is current shipping node.
(1) but be shipping path tree root node Root with P1, Root is current Parent node, initial search direction is two-way, makes n=P1;
(2) calculate f (n), the n node pointer is inserted the OPEN table in proper order;
(3) shift out p from OPEN heading end, but p correspondence shipping point is starting point S;
(4) great circle line SE is order line segment aggregate Array[between connection S, E], Array[] as the shipping p-wire;
(5) order travels through Array[] judge whether line segment intersects with polygon, if great circle line SE does not intersect (promptly not passing through land, barrier etc.) with any polygon, but then great circle line SE is the shipping line of point-to-point transmission, to (8) step; Otherwise, to (6) step;
(6), adopt point to polygon point of contact strategy, but zequin S and write down the corresponding direction of search to intersecting with p-wire and apart from the nearest polygonal shipping point of starting point according to the direction of search.
A) two-way, but a shipping point respectively searched for towards clockwise, counter clockwise direction respectively;
B) clockwise, but a shipping point searched for toward the clockwise direction;
C) counterclockwise, but towards counterclockwise searching for a shipping point.
Judge but whether each shipping point departs from objectives.If depart from objectives, but, adopt point, but but calculate and replace the replacement shipping point of current shipping point to the local point of contact of polygon strategy according to this shipping point direction.
(7) but be new terminal point with shipping point TP respectively, according to (2), (3), (4), (5) but recursive calculation starting point S is the shipping line of terminal point E to TP, the direction of search is the corresponding direction of search of TP;
(8) with Array[] create new node, add under current parent's node Parent as its child node.
Work as E==P2, but find the shipping line of P1 to P2,
A) create leaf node with P2, as the child node of new node;
B) calculating the new route distance is currPathLen;
C) upgrade shortest path length (PathLen=(PathLen==∞) currPathLen:Min (PathLen, currPathLen)) in the present tree.
As E ≠ P2,
A) calculate present node evaluation function f (E);
B) if f (E) 〉=PathLen, mark stops to change step (3) from present node search;
C) the present node pointer inserts the OPEN table according to f (E) order;
D) new node is current parent's node Parent;
E) changeing step (4) search E is starting point S, but P2 is the shipping line of terminal point E, the direction of search be the E counterparty to.
(9) path of the leaf node of shortest path length PathLen correspondence (leaf node dates back to the reverse path of root node) is the path, the shortest leg of point-to-point transmission.
8. method according to claim 1 is characterized in that, described method is sought the singularity of footpath algorithm in the steamer line design by analyzing based on the leg of polar plot, the footpath algorithm is sought in the leg improve.
9. method according to claim 1, it is characterized in that, described method represented by polygon in polar plot at land, island and other barriers of world map, and the leg is sought the footpath and is polygon outside the point-to-point transmission generation and do not pass through polygonal communication path, finally finds optimum leg.
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