Abstract:
Automatic map generation is enabled by assigning priorities to each city in a list of cities under consideration for display on a map. A mapping engine determines a reference count for each city, indicating how frequently the city appears in one or more corpora of documents. Based on the reference count, and optionally upon other data such as population and political importance, a priority score is assigned to each city. Each city is then assigned to one of a plurality of categories according to the city&#39;s priority score. A map is then generated including cities from a specified highest number of categories. In one embodiment, cities from a higher-scored category are presented in a more significant way, e.g., in capital letters, bold type, etc., than are those in the next-highest scored category.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application 60/590,667, filed Jul. 23, 2004, and which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to computerized cartography. In particular, the present invention is directed to automatically assigning priorities to elements of a map based on properties of those elements.  
         [0004]     2. Description of the Related Art  
         [0005]     In making maps of states, provinces, countries, or regions, whether by hand or by using a computer program, it is a common practice to display cities as labeled points. Because not all cities are equally significant, cities are prioritized. More important cities—that is, cities that are more likely to be searched for on a map by a wide audience—are displayed and labeled; less important cities are displayed and labeled only where they do not interfere with the display of more important cities. Typically, when cities of various priorities are displayed, the most important cities are displayed with a larger or bolder symbol, and their names are displayed in larger or bolder type, or in all capital letters.  
         [0006]     The most common method of assigning priorities to cities is by population. Cities of population greater than some number p 1  are shown most prominently; cities with population less than p 1  but greater than some number p 2  are shown less prominently; cities with population less than p 2  but greater than some number p 3  are shown still less prominently; and so on, until cities with population less than some number p n  are not shown at all.  
         [0007]     However, a purely population-based method of assigning priorities is not always optimal. Some cities are important despite having small populations. For example, one typically expects to find a country&#39;s capital city on a map that includes that country. The capital of the United States, Washington, D.C., had a population of 572,059 in the 2000 census, making it only the 21st largest city in the United States—smaller than the city of Milwaukee, Wis., the 19th largest city. In spite of Milwaukee&#39;s greater population, it would seem odd to find Milwaukee but not Washington labeled on a national map. To account for this, mapmakers often make adjustments to the priorities of cities, in order to make sure that cities that are more important than their populations would imply are displayed appropriately.  
         [0008]     A difficulty in making these sorts of adjustments is that the mapmakers require knowledge about the politics and other cultural aspects of the country or region being mapped, and while it is relatively easy to determine that Washington is the capital of the United States, it is less obvious that Las Vegas, Nev. (population 478,434) is significantly more important from a mapping perspective than is Albuquerque, New Mexico (population 448,607). While both Las Vegas and Albuquerque are approximately the same size, Las Vegas is a major American tourism center (and thus is often searched for on a map), while Albuquerque is not.  
         [0009]     Now that an increasing number of maps are being produced using computers, it is desirable to automate the determination of which cities should be included without relying solely on population data and without requiring that the mapmakers have extensive political and cultural knowledge of the area being mapped.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention enables automatic map generation by assigning priorities to each city in a list of cities under consideration for display on a map. A mapping engine determines a reference count for each city, the reference count indicating how frequently the city appears in one or more corpora of documents. The corpus of documents itself is chosen as appropriate for the intended use of the map. Based on the reference count, and optionally upon other data such as population and political importance, a priority score is assigned to each city. Each city is then assigned to one of a plurality of categories according to the city&#39;s priority score. A map is then generated including cities from a specified highest number of categories. In one embodiment, cities from a higher-scored category are presented in a more significant way, e.g., in capital letters, bold type, etc., than are those in the next-highest scored category. In an alternative embodiment, cities are placed on the map without being assigned to categories. In this embodiment, a specified number of cities, e.g., the 10 cities with the highest priority scores, or the top 40, or the top 60, etc., are placed on the map. Alternatively, a top percentage of cities can be placed on the map, or in yet another alternative, a user can vary the number of cities placed on the map in real time to suit his preference. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a block diagram illustrating a system for automatically generating maps in accordance with an embodiment of the present invention.  
         [0012]      FIG. 2  is a flowchart illustrating a method for automatically generating maps in accordance with an embodiment of the present invention. 
     
    
       [0013]     The figures depict preferred embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     Referring now to  FIG. 1 , there is shown a system  100  for automatically generating maps in accordance with an embodiment of the present invention. System  100  includes a mapping engine  104 ; map source data store  102 ; and a corpus  106 . Also shown is an output map  108 . Map  108  in one embodiment is a paper or other physical map; in an alternative embodiment, map  108  is provided electronically, e.g., on a web page. The functionality of the mapping engine is described below with respect to  FIG. 2 .  
         [0015]     Map source data  102  includes a list of cities and attributes of each city. In one embodiment, attributes include location and population. In another embodiment, attributes also include additional data about each city, such as whether it is the capital of the country or a region, etc. Map source data  102  can originate from a variety of sources, such as a census bureau, ministry of commerce, post office, commercial vendor, etc.  
         [0016]     Typically, there are more cities included in source data  102  than can be accommodated by the map  108  because of the map&#39;s size. Accordingly, a subset of the cities must be selected to place on the map  108 , and subsets of that subset must be selected to be displayed with greater or lesser prominence. This selection is performed by mapping engine  104 .  
         [0017]     Mapping engine  104  assigns priorities to each city in the map source data  102 . Priorities are determined according to the frequency with which cities occur in the corpus of documents  106 . The corpus of documents  106  is chosen as appropriate for the intended use of the map. For example, in building a map for general use on the World Wide Web, corpus  106  preferably includes a set of Web pages indexed by a search engine. The number of references to a city in the corpus  106  can be determined, e.g., by performing a search for a string of the form “&lt;city name&gt;, &lt;state abbreviation&gt;” or “&lt;city name&gt;, &lt;state name&gt;”. There are several known methods for performing searches for terms in a corpus, and any can be used by system  100  to obtain a count for the frequency of each city in the corpus  106 . In one embodiment, the metric used by mapping engine  104  is the number of pages that include the city name. In an alternative embodiment, the count is the number of occurrences of the city name—that is, a city that appears twice in a page is counted twice, whereas in the previous embodiment it is counted only once.  
         [0018]     In another embodiment, system  100  is used to build a map  108  for use on a web site that provides news. In such an instance, the corpus  106  includes archives of news stories. Consequently, the map  108  generated by mapping engine  104  will include cities in which news happens (or is reported on) more often.  
         [0019]     In another embodiment, map  108  is generated for use on a Web site devoted to a specialized topic of interest, e.g., California history. In this embodiment, mapping engine  104  searches a corpus of documents relating to California history and counts the number of references to each city. As an additional example, in building a map for reference within a company, the corpus  106  can consist of the customer list and each customer located in a city can be counted as a reference for that city.  
         [0020]     Once determined, the reference count—i.e. the number of times each city is counted in the corpus—is used by mapping engine  104  to determine a priority order, i.e. an ordered list of cities sorted by importance. In one embodiment, the priority order is obtained by combining a reference count c of each city with a population p by multiplying each by some constant, k 1  and k 2 , respectively, and adding the results, resulting in a priority score k 1 ×c+k 2 ×p. In an alternative embodiment, the priority score is obtained by performing the same operation with the logarithms of these numbers (k 1 ×log c+k 2 ×log p). Mapping engine  104  then preferably sorts the cities in order of descending priority score, i.e., considering cities with a greater priority score to be more important, breaking ties in an arbitrary manner. In an alternative embodiment, mapping engine  104  sorts the cities in order of ascending priority score.  
         [0021]     In another embodiment, each city is ranked solely according to its population, and again solely according to its reference count. For example, in generating a map of the United States, if Washington, D.C. is the most frequently-mentioned city in corpus  106 , its rank is 1 with respect to reference count. Washington is the 21st most populous city in the United States, so its rank is 21 with respect to population. These rank numbers are then combined to obtain a final priority score based on the combined rankings. For example, they may be combined simply by taking the lesser of the two numbers, so that both New York (which has rank of 1 with respect to population) and Washington (which has a rank of 1 with respect to reference count) have a priority score of 1. Alternatively, the rank numbers may be weighted prior to being combined, in a manner similar to that described above for combining population and reference count. After the rank numbers are combined, mapping engine  104  then sorts the cities by priority score.  
         [0022]     In another embodiment, cities are ordered in decreasing order by reference count, without considering population. Using the formula described above, this can be expressed as k 1 ×c+k 2 ×p, where k 1 =1 and k 2 =0.  
         [0023]     In a preferred embodiment, each city is assigned to one of a plurality of categories according to the city&#39;s rank. The rank threshold between categories can be assigned in a variety of ways. For example, the rank thresholds in one embodiment are determined at the outset, e.g., the 10 highest-ranked cities are assigned to the first category, the next 40 to the second category, etc. Alternatively, a percentage threshold is used, e.g., the top-ranked 1% of the cities are assigned to the first category, the next-ranked 4% of the cities to the second category, etc. In another embodiment, the rank thresholds are determined by the user according to his taste.  
         [0024]     Referring now to  FIG. 2 , there is shown a flowchart illustrating a method for automatically generating maps in accordance with an embodiment of the present invention. First, mapping engine  104  determines  202  a reference count for each city in map source data  102  as described above. A priority score is then assigned  204  to the city by combining its population and its reference count, or its population rank and its reference count rank, as described above. Next, mapping engine  104  determines  206  a priority score threshold for each category. As described above, thresholds can be assigned either automatically or by the user. Using the determined thresholds, mapping engine  104  then assigns b08 each city to a category. Finally, mapping engine  104  generates  210  a map  108 , including cities assigned to the top categories. In an alternative embodiment, cities are not assigned to categories, and mapping engine  104  generates map  108  by selecting the n most frequently occurring cities in the corpus  106  and including them on the generated map  108 .  
         [0025]     In an alternative embodiment, two or more different corpora are used to obtain reference counts. The reference count for each city and from each corpus is weighted and then combined with the reference counts from the additional corpora, and optionally population, to determine a priority score. Alternatively, rankings can be determined for each city relative to each corpus according to the manner described above for a single corpus and then combined, optionally with population ranking.  
         [0026]     Although described so far in the context of locating cities on a map, the present invention also has application to locating other kinds of objects on a map—counties, countries, parks, airports, etc. That is, any entity for which references can be counted in a corpus can be mapped by system  100  according to the methods described above.  
         [0027]     In an alternative embodiment, the age of documents in the corpus  106  influences the reference count of a city. If newer documents in the corpus are more important than older documents, a sliding scale is used in which references in newer documents count more heavily than those in older documents. In one embodiment, a reference in a document that is t days old is counted as ce −kt  references, where c and k are constants and e is the base of natural logarithms.  
         [0028]     In an alternative embodiment, corpus  106  includes queries to a search engine, so that a large number of queries about a city causes a large reference count, even if there are not many references to the city in the corpus.  
         [0029]     The present invention provides a way of frequently and automatically redrawing a map for convenient reference. Suppose, for example, that a news-related Web site provides a map of the United States for reference by visitors to its site. The prioritization of cities in map source data  102  by mapping engine  104  is preferably automated using a count of references in a corpus  106  of recent news stories as the reference count, and the map  108  is redrawn automatically at specified intervals, for example, weekly or nightly, or even on demand. If a news story takes place in an otherwise unimportant city—say, Victorville, Calif.—the number of references to that city will increase, and the increased number of references will literally put the city on the map, automatically.  
         [0030]     In one embodiment, the corpus  106  is further restricted to include only web pages written in a certain language or languages. So, for example, a corpus of French-language documents can be used to prioritize cities on a map of Spain, thus showing those Spanish cities that are important to speakers of French.  
         [0031]     The present invention has been described in particular detail with respect to a limited number of embodiments. Those of skill in the art will appreciate that the invention may additionally be practiced in other embodiments. First, the particular naming of the components, capitalization of terms, the attributes, data structures, or any other programming or structural aspect is not mandatory or significant, and the mechanisms that implement the invention or its features may have different names, formats, or protocols. Further, the system may be implemented via a combination of hardware and software, as described, or entirely in hardware elements. Also, the particular division of functionality between the various system components described herein is merely exemplary, and not mandatory; functions performed by a single system component may instead be performed by multiple components, and functions performed by multiple components may instead performed by a single component. For example, the particular functions of counting references, generating a priority score, and sorting the score and so forth may be provided in many modules or in one module.  
         [0032]     Some portions of the above description present the feature of the preferred embodiments of the present invention in terms of algorithms and symbolic representations of operations on information. These algorithmic descriptions and representations are the means used by those skilled in the art of computerized cartography to most effectively convey the substance of their work to others skilled in the art. These operations, while described functionally or logically, are understood to be implemented by computer programs. Furthermore, it has also proven convenient at times, to refer to these arrangements of operations as modules or code devices, without loss of generality.  
         [0033]     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the present discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system memories or registers or other such information storage, transmission or display devices.  
         [0034]     Certain aspects of the present invention include process steps and instructions described herein in the form of an algorithm. It should be noted that the process steps and instructions of the present invention could be embodied in software, firmware or hardware, and when embodied in software, could be downloaded to reside on and be operated from different platforms used by real time network operating systems.  
         [0035]     The present invention also relates to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, application specific integrated circuits (ASICs), or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus. Furthermore, the computers referred to in the specification may include a single processor or may be architectures employing multiple processor designs for increased computing capability.  
         [0036]     The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may also be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description above. In addition, the present invention is not described with reference to any particular programming language. It is appreciated that a variety of programming languages may be used to implement the teachings of the present invention as described herein, and any references to specific languages are provided for disclosure of enablement and best mode of the present invention.  
         [0037]     Finally, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention.