A mobile device for processing and displaying location information, and a method for processing location information in mobile devices

The invention concerns in general the task of processing location information in mobile devices and presenting a human user with location-indicating data on a display. Especially the invention concerns a method and a system that enable processing and displaying location-related data globally with reasonable requirements for device complexity.

The widespread capability of mobile devices to create, process and display loca- tion-indicating data anywhere on the Earth is to the credit of satellite-based systems such as the GPS (Global Positioning System). A mobile device receives accurately timed transmissions from a number of satellites and uses the timing and other characteristics of the transmissions to calculate its location.

The bottleneck of turning mere locating capability into useful, mobile navigational aids has traditionally been the question, how should the mobile device indicate the calculated position to the user in relation with other geographical data. The traditional solution is to store a digitized map in a memory and to make the device select and display a suitably located portion of the map, with an icon indicating the calculated current position on the display. Digitized maps are problematic, be- cause they easily consume relatively large amounts of memory, and because the availability of accurate digitized geographic information in a reasonably compatible form may be scarce especially in remote areas or places that are private or of interest to national security or commercial secrecy. Additionally digital maps, like all maps, become obsolete relatively quickly especially in areas that undergo busy development, which causes a frequent need to replace older map versions with updated ones. The large amount of data included in digitized maps has required the mobile device to have a large memory and a high processing capacity, and many map-based applications have thus developed more into full-scale computer- based solutions that require a high level of skill and understanding of geographic information systems.

Another drawback of known digitized map is the lack of interoperability between maps and processing systems of different manufacturers. Solutions that rely on continuously obtaining the most actual digital geographic information from a cen-

tralized server have also the drawback of being dependent on a reliable communications connection with the server.

An objective of the present invention is to present a method and a system for processing and displaying location-indicating data on the display of a mobile de- vice with low requirements concerning device complexity and user skills. Another objective of the present invention is to present a mobile electronic navigational aid with high potential for truly global coverage. Yet another objective of the present invention is to enhance the versatility of digital geographical information so that it could be used in a wide variety of systems and devices. The objectives of the invention are achieved by defining a concise and consistent representation for digital data that describes places and landmark points, and providing the user of a portable device with the possibility of selecting the places landmark points to be displayed according to factors like landmark class or distance from current location. A mobile device according to the present invention is characterized by the features listed in the characterising part of the independent claim directed to a mobile device.

A method according to the present invention is characterized by the features listed in the characterising part of the independent claim directed to a method. A computer program product according to the present invention is characterized by the features listed in the characterising part of the independent claim directed to a computer program product.

A conventional digitized map often comprises a very large amount of information, most of which is very seldom needed. A user who tries to navigate or track his route will mostly like to utilize easily recognizable places and landmarks, such as cities, towns, villages, hotels, shopping malls, schools, restaurants, religious buildings, gas stations and others. According to an aspect of the present invention, such places and landmarks are represented with very concise character strings that include fields for name information, country code, type, and exact location in a selected coordinate system. A collection of such character strings constitutes a so- called location directory.

Due to the conciseness of the character string representation it is easy to store location directories of very large coverage in a relatively small memory space. In an

exemplary embodiment the character string representation might have a character count between a minimum of 24 characters and a maximum of 118 characters. Assuming that each character reserves one byte of eight bits, a small portable memory device with 2 gigabytes storage capacity could store between roughly 17 million and 80 million such character strings. Taken that the habitable land area of the Earth is around 64 million square kilometres, a database with an average of ten stored places and landmarks per each habitable square kilometre of the Earth would only fill a memory space between 15 and 75 gigabytes, which at the time of writing this description would already fit into a single USB (Universal Serial Bus) flash drive. A similarly dimensioned single memory device could store a location directory database of the whole United States with an average of 80 stored places and landmarks per each square kilometre, including deserts, mountains and water areas.

A mobile device according to an embodiment of the invention is capable of dis- playing selected points of the location directory. A user may select the points to be displayed according to his preferences, for example based on the contents of the type field in the character string representation. In many cases it is advantageous to make the device use different graphical icons for displayed points of different type. The device may also have an automatic filtering function in order to only se- lect certain ones of the possible points for display, for example so that if the display is zoomed to cover a large geographical area, only the most important points like big cities are displayed.

The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Fig. 1 illustrates schematically a mobile device according to an embodiment of the invention,

fig. 2 illustrates an exemplary data structure and its use as a location directory, fig. 3 illustrates an exemplary displayed image, fig. 4 illustrates another exemplary displayed image, fig. 5 illustrates schematically a method and a computer program product according to an embodiment of the invention, fig. 6 illustrates the appearance of a pop-up menu on a display, fig. 7 illustrates aspects of a method and a computer program product according to an embodiment of the invention, and fig. 8 illustrates an example of selecting records for display.

Fig. 1 illustrates schematically a mobile device 101 , which comprises a display 102 for displaying location-related information. The mobile device 101 comprises a positioning part 103, which could be for example a general-purpose GPS receiver and which is capable of producing location information that indicates the current location of the mobile device 101 in a certain coordinate system. Additionally the mobile device 101 comprises a memory 104 for storing a location directory, and a processing part 105, which is adapted to use the location information from the positioning part 103 as an indicator to determine, which points should be read from the location directory and displayed on the display 102. The mobile device 101 comprises also input means 106, through which a user may give operating commands. As an example, the input means 106 may comprise pressable keys. In its simplest form the operation of the mobile device 101 includes displaying on the display 102 an indicator of the current location, along with indicators of one or more points read from the location directory in graphical form so that the geometric relations of the indicators on the display correspond to the directions and distances between the corresponding locations in the real world.

Let us first examine an exemplary way of storing information concerning places and landmarks in the location directory. Fig. 2 illustrates schematically an exemplary data structure that can be used as a location directory 201. It comprises a large number of records 202. Each record comprises a number of fields, of which fields 211 to 217 are shown. For short reference, the fields have been named as

F1 , F2, F3, F4, F5, F6, and F7. In this exemplary case the fields have the following purposes and maximum lengths.

Table 1 : exemplary fields of a record.

We may assume that a particular character like comma is used as a field delimiter. Separating seven fields from each other requires six field delimiters. Using the exemplary maximum field lengths of table 1 we get a maximum length of 118 characters for a record. In a particular record one or more of the fields may be empty. Also in many fields it is not necessary to use the full length of the field in all re- cords. For example, if field F1 has only one character, fields F2 and F3 are empty, and fields F6 and F7 have only 7 characters, the record could be as short as 24 characters (1 in field F1 , 2 in field F4, 1 in field F5, 7 in each of fields F6 and F7, and 6 field delimiter characters). Even shorter records are possible, for example if an empty field F5 is defined to mean one specific type, and/or if some country has a single-character country code, and/or if the coordinates of a point happen to be so exactly on the grid lines of the coordinate system that only few numerals are needed in any of fields F6 or F7.

A hierarchical naming structure is advantageous in many cases, which explains the allocation of three fields to names. One of the name fields, for example F1 , contains the lowest hierarchy name or primary location. Typically this is a point with a known, point-like absolute location, such as a building, intersection, village

centre or the like. Another name field, like F2, contains the next upper hierarchy level name (if any), such as the name of the municipality or the like within which the point is located, so that the area known by that name typically contains a number of points that have individual names in their F1 field. Yet another name field, like F3, contains the highest hierarchy level name (if any), such as the name of a province or state, so that the area known by that name typically contains a number of smaller areas that have individual names in their F2 field. Country codes are typically standardized identifiers like those found in the Federal Information Processing standard / International Standardization Organization classification FIPS 10-4/ISO-2.

Concerning types we may assume that a relatively small number of types have been defined. Exemplary types and their type identifier characters are the following.

Table 2: exemplary types

For expressing coordinates there are a number of possibilities. Since the most widely used global coordinate system is the WGS84 (World Geodetic System 84), it is a straightforward selection also here. An exemplary convention is to express coordinates in signed decimal degrees, so that an unsigned latitude (longitude) is in the northern (eastern) hemisphere and a minus-signed latitude (longitude) is in the southern (western) hemisphere.

Fig. 3 illustrates an exemplary case of displaying location-related information on the display of a mobile device. The exemplary displayed image contains three zones: the title zone 301 , the location information zone 302 and the functions leg-

end zone 303. The title zone 301 may contain a title 304 of the application program that is processing and displaying the location information, as well as symbols that inform the user about the operational state of the program; a graphical GPS signal strength indicator 305 is shown as an example. Other elements that could be displayed in the title zone include, but are not limited to, indicators of the general operational state of the device that executes the program. For example, if the device is an intelligent mobile phone, the title zone could include indicators of the currently selected network, signal strength of the serving base station, indicators of other programs running in the background, and the like. At the middle of the location information zone 302 is a pointer 306, which represents the current position of the mobile device. Also in the location information zone 302 there are displayed the symbols of those points that have been read from the location directory and selected for display. As an example there is the symbol 307 of a city named Bacolod. A further element displayed in the location information zone 302 is a scale bar 308, which indicates the scale of the graphical illustration. As an important difference to for example the commonly used vehicle navigation programs known at the time of writing this description, the displayed image typically does not contain any map-like continuous geographical description of the surrounding area, but only the points and some information related to them, like the name of each point. The background behind the displayed points and information is blank, in the sense that it does not attempt to convey any geographical information to the user. Depending on choices of the user interface designer, the blank background may be filled with an even background color, or a gradient fill color, or a simple constant pattern, or any other graphics that do not have any association with the geographical surroundings of the current location.

The selected points are displayed in the location information zone 302 so that their directions and distances from the pointer 306 correspond to the actual directions and distances from the present location of the mobile device to the corresponding physical locations, taken the scale indicated by the scale bar 302 into account. Ac- cording to the usual convention of map drawing, north is towards the top of the map (a dial card or a directional arrow could be displayed in the location information zone to confirm the direction of compass points). Thus the user sees that the large city nearest to his current location is Cebu, located little less than 200 kilometres to east north-east, followed by Mandaue and Dumaguete at about 370 kilometres to north-east and south-west respectively, while Bacolod is about 400 kilometres to north-west.

In this embodiment of the invention the pointer 306 is always at the centre of the location information zone. It is possible to present embodiments of the invention in which the user may use arrow keys or other control means in the device to change the mutual displaying aspect of the pointer and the other elements, for example so that he moves the pointer to some other part of the location information zone, or changes the displayed direction of compass points, or so that he examines a completely different area some points of which are stored in the location directory. However, a simple embodiment where an indicator of the current location of the device is always displayed in the centre of the location information zone ensures simple operation and maximum compatibility with a wide range of possible mobile devices.

The functions legend zone 303 contains two function designators 309 and 310. Many existing programmable mobile devices, such as intelligent mobile phones and PDA (Personal Digital Assistant) devices, have so-called softkeys located close to one or more edges of their display. Pressing a softkey causes an action that depends on the currently executed software, and it is customary to make the software display legends of such actions next to the softkeys. In fig. 3 we assume that there are two softkeys located close to the lower edge of the illustrated display, so that pressing the left softkey opens an Options menu and pressing the right softkey closes the Map application. It is possible to customize the processing software so that it recognizes the type of device that it resides in, and selects the number and position of displayed function designators according to the number and position of softkeys that exist in that device.

Fig. 4 illustrates an alternative case of displaying location-related information. This time the user has zoomed to a smaller scale and there is a wider variety of different type points shown on the display. While in fig. 3 all displayed points were cities, in fig. 4 there is a symbol 401 for a city, a symbol 402 for a town, a symbol 403 for a point of interest, a symbol 404 for a user-defined point, and a symbol 405 for a village. These point types and their corresponding graphical symbols are natu- rally just examples; point types and graphical symbols could be defined in numerous other ways.

Fig. 5 is a simple flow diagram illustration of a method and computer program product according to an embodiment of the invention. The execution starts at step 501 typically so that the user selects an icon of the appropriate application pro- gram from a graphically displayed menu. Step 502 represents initialization, i.e. ensuring that the execution of the program begins with appropriate initial information.

At step 503 the current location of the device is obtained from the GPS receiver or corresponding positioning part. At step 504 the location directory is consulted in order to find those points that should be displayed, taken the most recently obtained current location information and factors like selected display scale and filter- ing of points.

Filtering means that there may be both manually and automatically set criteria for selecting, what kind of points should be displayed in a particular situation. Basically all such points could be displayed, the location (longitude and latitude) of which is close enough to the current location of the device so that at the selected scale the points would appear in the area that fits in the location information zone of the display. Above we have discussed some exemplary types of points, some of which are associated with the assumed geographical importance: for example, a large city is geographically more important than a small village. An example of an automatically set criterion is a rule, according to which if the currently selected dis- play scale is such that the scale bar on the display represents 100 kilometres or more, city-type points are displayed but town-type and village-type points are not (because it is assumed that there would be so many of them that the location information zone would become completely clogged). Another example is to take dynamically into account some predetermined importance of points, so that each time when the purely distance-based check in the location directory gives more points than some predetermined limit, only as many as said limit are displayed, in decreasing order of importance. How the concept of importance is defined is not material to the present invention; in addition to the geographical importance outlined above one could assume e.g. that the user's own points are more important than default points of the location directory.

Setting criteria manually means that the user may indicate his own preferences to the application program. Examples of manual criterion-setting are discussed later in this description.

At step 505 positions are calculated for the graphical representations of the se- lected points, i.e the image to be displayed is prepared. Step 505 may include also other kinds of decisions related to graphical representation, like decisions about on which side of the graphical symbol of each point its name should appear. At step

506 the completed image is displayed. The loop consisting of steps 503 to 507 is continuously repeated until it is found at step 507 that the user has given a com- mand to abort the application program, which leads to the end state 508.

Fig. 6 is an exemplary illustration of how the display may look like when the user has pressed the softkey, next to which the text Option" was displayed. Pressing the softkey has caused a pop-up menu 601 to appear and the previous text "Options" at the functions legend zone to be replaced with the text "Select". The pop- up menu 601 displays indicators (here: names) of additional functions that the user may wish to activate. Fig. 7 illustrates the organisation and operation of such additional functions in the form of a simple state diagram.

Regardless of which state the device was in when the Option" softkey was pressed, the execution of the application software reacts with a transition to the Display Options Menu state 701 , in which it displays the pop-up menu and waits for further commands. Depending on which function the user selects, different state transitions occur. States 711 , 712 and 713 are related to managing the location directory. At state 711 the application program offers the user the possibility of creating and storing a new point, preferably so that at state 711 a data input form is displayed, with the current location of the device appearing as a default at the latitude and longitude fields. When the user has entered all desired data into the fields of the data input form, the application program stores a new record into the location directory with the corresponding data appearing in the fields of the record. Pressing "Exit" or otherwise indicating readiness causes a transition back to state 701. At state 712 the application program offers the user the possibility of deleting a selected point or selected points from the location directory, and at state 713 the application program offers the user the possibility of changing the contents of the fields in a record that represents an existing point in the location directory. In each case, pressing "Exit" or otherwise indicating readiness causes a transition back to state 701.

States 721 and 722 involve changing the scale of the displayed image into larger and smaller direction respectively. According to a preferable embodiment the application program is capable of displaying the image at various predetermined scales ranging from very coarse (scale bar length hundreds of kilometres) to very fine (scale bar length in the order of some tens of meters). There may be even a relatively large number of predetermined scales, like one hundred. Zooming in or out is a simple one-step operation, so a return transition from states 721 and 722 to state 701 occurs automatically.

States 731 to 735 are associated with manually setting criteria for filtering the se- lected points. If originally all types of points were displayed, entering one of states

731 to 735 causes a criterion to be set, according to which only points of the cor-

responding type are displayed. The criterion is stored for use, and return to state 701 occurs automatically. If one such criterion is in use, the user may switch it off and return to displaying all types of points by visiting the same one of states 731 to 735 again (i.e. each of these states toggles the corresponding criterion on and off). Typically a user is interested in cities when using a large scale on the display, and villages when using a smaller scale. Thus it may be advantageous to associate each of states 731 , 732 and 733 with an automatic zooming step, so that if the user selects e.g. to view only cities according to state 731 , that might cause the application program to automatically zoom out to some predefined large scale that is typically reasonable when displaying city-type points. Correspondingly if the user selects to view only towns or villages according to states 732 and 733 respectively, the application program could automatically zoom in into some predefined smaler scale that is typically meaningful reasonable when displaying points of those types. Fig. 8 illustrates schematically an exemplary method for selecting points for display from the location directory. In other words, fig. 8 illustrates an example of what happens in step 504 of fig. 5. The current location (XO ₁ YO) of the mobile device, as well as the currently valid scale and filtering criteria, are read at step 801. The scale is used at step 802 to derive the limits XL and YL that determine, how close the longitude and latitude of a point must be to the current location of the mobile device in order to make the point fall into the displayed area. A new record with location information (X, Y) is read from the location directory at step 803, and its closeness to the current location is checked at step 804. If the point is close enough to be displayed with the current scale, there follows an additional screen- ing at step 805 to see whether the point matches the currently valid filtering criteria. In a positive case the point is selected for display at step 806. Step 807 is a check to see whether all points were considered already. Negative findings at steps 804 and 805 lead directly to step 807. If there are still unexamined points in the location directory, the loop is started again from step 803 by reading the next record.

Step 808 is a check to see, whether the selected points would all fit nicely into the displayed image. If there are too many of them so that the image would become clogged, the least important are deselected at step 809. The mutual importance of points may be determined in a way described earlier, and/or overlapping points will be considered so that of points that are located closer to each other than some predetermined limit, only one is chosen for display arbitrarily or according to some

rule. The remaining selected records are output at step 810 for composing the image to be displayed. A sequential search through the whole location direction each time is not very efficient, but serves well here as an illustrative example. In practical implementations the way of searching through the location directory to find points close enough to be displayed would be performed through some more advanced searching strategy, as is well known in the art.

The embodiments of the invention described above are examples only and should not be construed to have a limiting effect. For example, even if the positioning part has been illustrated above to form an integral part of the device that executes the application program, it is possible to present an embodiment of the invention in which the application program runs in a device separate from that device that creates the current location information. An example is a coupling of a PDA device to an external GPS receiver through a local communications link. Another example of possible variations to the configurations described so far concerns the handling and updating of the location directory. Previously we have assumed that the whole location directory is completely stored in the memory of the device that executes the application program. However, it is possible to have only a part of the location directory stored locally, and update it with additional information at times when a communications connection to a centralized location directory server is available. Even if a location directory with global coverage was originally stored completely in the local memory, having a communications connection with a centralized location directory server from time to time is advantageous in order to get the locally stored location directory updated with the most recent information.