Abstract:
Imagery, video, maps or signs are embedded with plural-bit data in the form of digital watermarking. In one embodiment, a method includes obtaining a media signal representing an image or video; introducing digital watermarking into the media signal, the digital watermarking slightly altering samples of the media signal; and the digital watermarking changing across the media signal so as to convey first information related to at least a first area depicted in the image or within data representing a first portion of the video in the media signal and second, different information related to at least a second area depicted in the image or within data representing a second portion of the video in the media signal. Other embodiments are provided as well.

Description:
RELATED APPLICATION DATA 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 09/833,013, filed Apr. 10, 2001 (published as US 2002-0147910 A1). These patent documents are hereby incorporated by reference. 
     
     FIELD OF THE INVENTION  
       [0002]    The present invention relates to navigation and map orientation, and is particularly illustrated with reference to maps and signs embedded with digital watermarks. 
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0003]    A map is both a beloved and bewildering companion to those who choose to navigate an unfamiliar city or traverse across country to find a blissful vacation spot. Map navigation becomes even more difficult for those who retreat into the wilderness, some becoming lost, unable to traverse the unfamiliar terrain with a map. 
         [0004]    Countless children, stuffed into the backseats of vacation-bound station wagons, sport utility vehicles and Volkswagen bugs, have pleaded to know if “we are there yet.” Befuddled parents search for convincing answers as they unfold yet another map. 
         [0005]    In some circles, orienteering and adventure racing rise to the level of competition, drawing crowds of participants and network audiences. Such competitions force participants to navigate through mountains, streams, and deserts, often guided only by a compass and map. 
         [0006]    Many young geography students, when presented with a world or area map, struggle to accurately place themselves within a map to determine their relationship to various area or world locations. 
         [0007]    Commercial and recreational boats and aircraft often travel through unfamiliar areas and must skillfully navigate in order to reach their intended destinations. 
         [0008]    Global positioning systems (GPS) have improved navigation by providing accurate location feedback. As will be appreciated by those skilled in the art, military and civilian water, ground, and airborne vehicles often use GPS systems for navigation. GPS is a satellite-based radio navigation system capable of providing continuous position, velocity, and time information. GPS receiver units receive positioning signals from a constellation of satellites deployed in various orbits about earth (e.g., 12-hour orbits). The satellites continuously emit electronic GPS signals (or telemetry) for reception by ground, airborne, or watercraft receiver units. By receiving GPS signals from a plurality of satellites, a properly configured receiver unit can accurately determine its position in three dimensions (e.g., longitude, latitude, and altitude). 
         [0009]    There are many known GPS systems. For example, U.S. Pat. No. 5,990,826 discloses an interbuilding and urban canyon extension solution for global positioning systems. 
         [0010]    U.S. Pat. No. 5,861,841 discloses a compact GPS receiver/processor. The GPS system including an antenna to receive Global Positioning System (GPS) signals from two or more GPS satellites and a credit card size GPS signal processing Smartcard. The Smartcard is attached to the antenna that receives the GPS signals and determines and displays the present position of the antenna. 
         [0011]    U.S. Pat. No. 5,964,821 discloses a navigation system for offering navigational assistance to a mobile user. The navigation system receives GPS position information signals, which are processed to determine current position latitude and longitude coordinates and direction of travel. 
         [0012]    Of course, there are many other GPS systems known to those of ordinary skill in the art. 
         [0013]    The present invention employs digital watermarking techniques to even further ease navigation and map orientation. In some embodiments, digital watermarking techniques are combined with GPS systems. Applications of the present invention include implementations in fields such as government work and field reconnaissance, commercial or recreational boating, hiking, mountaineering, travel, orienteering, geography, education, exploration, entertainment, sight seeing, etc. 
         [0014]    Digital watermarking, a form of steganography, is the science of encoding physical and electronic objects with plural-bit digital data, in such a manner that the data is essentially hidden from human perception, yet can be recovered by computer analysis. In physical objects, the data may be encoded in the form of surface texturing, or printing. Such marking can be detected from optical scan data, e.g., from a scanner, optical reader, input device, digital camera, or web cam. In electronic objects (e.g., digital audio or imagery—including video), the data may be encoded as slight variations in sample values. Or, if the object is represented in a so-called orthogonal domain (also termed “non-perceptual,” e.g., MPEG, DCT, wavelet, etc.), the data may be encoded as slight variations in quantization values or levels. The assignee&#39;s U.S. Pat. No. 6,122,403 and U.S. application Ser. No. 09/503,881 (now U.S. Pat. No. 6,614,914) are illustrative of certain watermarking technologies. 
         [0015]    Digital watermarking systems typically have two primary components: an encoder that embeds the watermark in a host media signal, and a decoder that detects and reads the embedded watermark from a signal suspected of containing a watermark (e.g., a suspect signal). The encoder embeds a watermark by altering the host media signal. The decoder component analyzes a suspect signal to detect whether a watermark is present. In applications where the watermark encodes information, the decoder extracts this information from the detected watermark. 
         [0016]    The analysis of the detected data can be accomplished in various known ways. Presently, most steganographic decoding relies on general purpose microprocessors that are programmed by suitable software instructions to perform the necessary analysis. Other arrangements, such as using dedicated hardware, reprogrammable gate arrays, or other techniques, can of course be used. 
         [0017]    Determining orientation of embedded data can be discerned by reference to visual clues. For example, some objects include subliminal graticule data, or other calibration data, steganographically encoded with the embedded data to aid in determining orientation. Others objects can employ overt markings, either placed for that sole purpose (e.g. reference lines or fiducials), or serving another purpose as well (e.g. lines of text), to discern orientation. Edge-detection algorithms can also be employed to deduce the orientation of the object by reference to its edges. 
         [0018]    In one example, subliminal graticule data can be sensed to identify the locations within the image data where the binary data is encoded. The nominal luminance of each patch before encoding (e.g., background shading on a map) is slightly increased or decreased to encode a binary “1” or “0.” The change is slight enough to be generally imperceptible to human observers, yet statistically detectable from the image data. Preferably, the degree of change is adapted to the character of the underlying image, with relatively greater changes being made in regions where the human eye is less likely to notice them. Each area thus encoded can convey plural bits of data (e.g., 16-256 bits). 
         [0019]    One problem that arises in many watermarking applications is that of object or positioning corruption. If the object is reproduced, skewed, or distorted, in some manner such that the content presented for watermark decoding is not identical to the object as originally watermarked, then the decoding process may be unable to recognize and decode the watermark. To deal with such problems, the watermark can convey a reference signal. The reference signal is of such a character as to permit its detection even in the presence of relatively severe distortion. Once found, the attributes of the distorted reference signal can be used to quantify the content&#39;s distortion. Watermark decoding can then proceed—informed by information about the particular distortion present. 
         [0020]    The assignee&#39;s U.S. application Ser. Nos. 09/503,881 (now U.S. Pat. No. 6,614,914) and 09/452,023 (now U.S. Pat. No. 6,408,082) detail certain reference signals, and processing methods, that permit such watermark decoding even in the presence of distortion. In some image watermarking embodiments, the reference signal comprises a constellation of quasi-impulse functions in the Fourier magnitude domain, each with pseudorandom phase. To detect and quantify the distortion, the watermark decoder converts the watermarked image to the Fourier magnitude domain and then performs a log polar resampling of the Fourier magnitude image. A generalized matched filter correlates the known orientation signal with the re-sampled watermarked signal to find the rotation and scale parameters providing the highest correlation. The watermark decoder performs additional correlation operations between the phase information of the known orientation signal and the watermarked signal to determine translation parameters, which identify the origin of the watermark message signal. Having determined the rotation, scale and translation of the watermark signal, the reader then adjusts the image data to compensate for this distortion, and extracts the watermark message signal as described above. 
         [0021]    Such watermarking techniques, and many others known to those skilled in the art, may be suitably employed to improve navigation, easy road journeys and enhance education, among other benefits. 
         [0022]    The foregoing and other features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0023]      FIG. 1  illustrates a map, which is divided into blocks. 
           [0024]      FIG. 2  illustrates various components of a watermark reading device. 
           [0025]      FIG. 3  illustrates the device of  FIG. 2  in relation to the map of  FIG. 1 . 
           [0026]      FIG. 4  is a flow diagram illustrating a method according to the present invention. 
       
    
    
     DETAILED DESCRIPTION  
     Watermark Embedding 
       [0027]    In accordance with a first embodiment of the present invention, a map  10  includes plural-bit data steganographically encoded therein. (The term map is used broadly herein and includes, for example, navigational tools and documents, road maps, atlases, wilderness maps, area maps, city maps, tourist maps, location guides, walk or run routes, path-layouts, 3-demesional models, vegetation maps, building maps, structure maps, stadium seating and concert hall locations, park maps, amusement or theme park maps, DEM maps, master maps, topographical maps, globes, relief maps, to name just a few. A map may also include a digitized map for display on a monitor, TV, LCD, etc.). Map  10  can be printed or drawn on any suitable surface including paper, fibers, fabric, wood, plastic, metal, metal-alloys, objects, plaster, laminates, etc., etc. A digitized map image may include plural-bit data steganographically encoded therein. 
         [0028]    The encoding of the map can encompass artwork or printing on the map, the map&#39;s background, lines on the maps, a laminate layer applied to the map, surface texture, etc. If a photograph, line design, or drawing is present, it too can be encoded. A variety of watermark encoding techniques are detailed in the patent documents discussed herein; artisans in the field know many more. 
         [0029]    Preferably, map  10  is embedded with a plurality of watermarks. As shown in  FIG. 1 , map  10  is divided into a plurality of areas A-P (e.g., blocks, patches, or segments, etc.). Of course, the number of blocks or areas can be varied, with enhanced precision resulting from an increased number of blocks. Each area is preferably embedded with at least one watermark. (In one embodiment, each individual block is redundantly embedded with multiple copies of a respective unique watermark—further enhancing the robustness of the map. In another embodiment, some of the blocks are subdivided, with at least one unique watermark embedded in each subdivision.). 
         [0030]    A watermark typically includes a payload (e.g., 16-256 bits) that provides area (or location) identifying information. For example, the payload may include the geo-coordinates (e.g., “center lat: N34.4324352, long: W87.2883134; rot from N/S: 3.232; x2.343, y2.340, dx0.123, dy493, etc.”) for the center of the area, the coordinates of each area corner or boundary, the area of the boundary, a range of coordinates for the area, coordinates in relation to the overall area depicted by the map, and/or the coordinates for a dominate (or well-known) structure, road, area, etc., within the area block. (For example, area A is embedded with at least one watermark having coordinates corresponding to area A&#39;s center or corners, etc.). The payload may simply be a number that is associated with a block location on the map. For example, if a map comprises 32 by 64 watermarked blocks, each block is encoded with a number between 1 and 2048. 
         [0031]    Further, the payload may include additional fields, one conveying a map ID and another conveying the block number. The map ID may be used to identify the map as one of a collection of potentially many different maps. To program a map reader (as discussed below) for a particular map in the collection, the user passes the reader over the map to read the map ID (or simply enters the map ID). The reading device is then connected to a database, via a docking station at a personal computer or through a wireless connection. The reading device queries the database with the map ID and the database returns information associated with items of interest on the particular map (such as restaurants, scenic areas, camp sites, etc.) The user then disconnects the reader from the database and is ready to use the map. 
         [0032]    In another embodiment, some bits in the watermark payload identify the latitude/longitude of the map origin, while other payload bits identify the coverage extent of the map. Additional payload bits may even identify the offset of a chosen block from the origin. As an alternative, the lat/long and extents could be read from an initialization section, e.g., a map legend, or corner area, etc. 
         [0033]    As an alternative, the location information may include an index or identifier, which is used to interrogate a database to find physical coordinates or location information. Upon extraction by a watermark decoder, the index is provided to a database. The decoder may communicate with a database via a network (e.g., wireless network, LAN, WAN, the internet, intranet, etc.). Alternatively, the database may be maintained locally, or stored on a computer readable medium such as a compact disk (CD), magnetic tape, magnetic storage device (disk drive, removable media, floppy disks, etc.), electronic memory circuits, etc. Related information that is stored in the database is indexed via the watermark index. 
         [0034]    A grid (or orientation) signal can also be included in the watermark and/or location information. Preferably, the entire map uses the same grid signal, so that all blocks in a map can be used to determined rotation and scale of the map. Such a grid signal may assist in detecting watermarks. (Alternatively, such a grid signal can be used to help orient a map. For example, an orientation signal may be used to designate magnetic North, or another map orientation. Feedback can be supplied to a reader (e.g., watermark decoder) to help orient a watermark reader with respect to a map and the physical surrounding area. As discussed below, a watermark reader may be provided with compass-like functionality to assist with such orientation.). 
         [0035]    The watermark may be embedded such that it conveys both orientation and message information. For example, the modifications made to encode message symbols may be made in a manner that creates a recognizable pattern, such as a known array of peaks in a particular transform domain, such as the autocorrelation domain, the Fourier domain, or some other transform domain. One approach is to embed the message symbols by modulating a carrier signal with autocorrelation properties that form peaks in the autocorrelation domain. In particular, by performing an autocorrelation of an image captured of the watermarked map, the watermark detector generates peaks that can be compared with an expected pattern of peaks attributable to the carrier signal. The detector then performs pattern matching with the peaks to determine the scale and rotation of the captured image relative to the watermarked map. Another approach is to use peaks in a particular transform domain (such as the Fourier domain) for both orientation and message information. In this approach, the watermark is represented as collection of N possible peaks at particular locations in the Fourier magnitude domain. The detector first identifies some subset of the N peaks to determine orientation, and then determines message information by identifying the presence or absence of peaks at predetermined locations. 
         [0036]    In one embodiment, each block on a map has a similar payload structure, e.g., each including the same grid signal and perhaps the coverage area of the map (e.g., latitude/longitude, range of coordinates, etc., of the map.). The remaining payload bits would then be used to identify the individual areas (e.g., blocks A-P) on a map  10 . 
         [0037]    Phase-correlation can be employed to even further improve the location resolution within a map block. Once the detector has determined the rotation and scale of the captured image relative to the watermarked map, it can realign the captured image using these rotation and scale parameters. The watermarked block locations can then be detected by using the known phase attributes of the watermark signal and correlating these known attributes with the realigned, captured image. These block locations then serve as reference points for decoding watermark message data from a particular block. Also, in one embodiment, resolution down to a pixel within a block is achieved once rotation and scale are resolved. 
       Watermark Reading Device 
       [0038]    A watermark reading device can take various forms. Preferable among such forms is a handheld reading device  20 . (With reference to  FIG. 2 , a hand-held device  20  may allow better placement of the device in close proximity to map  10 , or sections of map  10  itself, permitting precision navigation. A hand-held reading device  20  is typically portable—an advantageous feature for outdoor and wilderness applications.). Examples of such hand-held device  20  include stand alone hardware implantations, portable computing devices, personal digital assistants (PDAs), portable devices such as those manufactured by Compaq (e.g., the iPac line) and Handspring, cellular and satellite phones, smart pens and watches, etc. 
         [0039]    A handheld reading device  20  preferably includes a general purpose or dedicated computer, incorporating electronic processing circuitry (e.g., a CPU)  22 , memory  24 , an interface  26  to an input device  28 , an output device  30  (e.g., a display screen, LED indicators, LED arrows, speakers, and/or audio-synthesis chip, etc.), and optionally a network connection  32 . (Of course, interface  26  may be integrated with other device  20  circuitry, particularly if input device  28  is built onboard device  20 . Also device  20  preferably includes sufficient bus or other structure to facility electronic signal communication between the various device components, where needed.). The network connection  32  can be used to connect, through a wireless or satellite connection to a network (e.g., intranet, internet, LAN, WAN, etc.). In one embodiment the input device (or reading device  20 ) is tethered to a desktop or laptop computer. A network connection is achieved via the connected computer. Preferably, a handheld reading device includes (or, alternatively, is in communication with) a global positioning system receiver  34 . As will be appreciated by one of ordinary skill in the art, suitable software programming instructions executing via CPU  22  can be used to effect various types of functionality (including watermark detection and reading) as discussed herein. 
         [0040]    The handheld reading device  20  includes (or is in communication with) an input device  28 . The input device  28  may include an optical reader, an imaging mouse, a digital camera, a laser or pen scanner, a digital eye module, etc. Digital eye modules (such as those provided by LightSurf, Inc.) typically include features such as a complete camera on a chip, CMOS imaging sensor, miniaturized lens and imaging software. Other imaging devices include a CCD image sensor. Of course, input devices can be packaged in variety of forms to suit particular applications. (In one embodiment, an input device  28  is tethered to a personal computer having watermark decoding software executing therein.). 
         [0041]    The handheld reading device  20  may include additional features to improve reading and facilitate accurate placement of the device  20  on map  10 . For example, the input device  28  may optionally include a targeting guide, such as a cross-hair-like viewer (or other visual indicator). A targeting guide helps achieve precise placement of the input device  28  on the map  10 . The area within the cross-hairs (or targeting guide) preferably corresponds with the area captured by the input device. (Alternatively, the area within the cross-hairs could also be a known offset from the area captured by the input device. Watermark rotation and scale information could be used to determine actual location.). In another embodiment, a see-through window is provided to locate and target an exact map location. (Of course, the input device  28  may employ a beam-splitter or reflective lens to ensure that the viewed area is the same as that captured by the input device  28 .). The viewable window area corresponds with that captured by the input device  28 . In still another embodiment, a camera-pen or laser-pointer allows a user to pin-point a map location, which is scanned (e.g., image capture). 
       User Applications 
       [0042]    A typical application of the present invention involves a map user placing a handheld reading device  20  (or an associated input device  28 ) near or on a map  10  ( FIG. 3 ). (Of course,  FIG. 3  is not intended to limit the size relationship between the map  10  and device  20 ). The input device  28  reads a map area (e.g., area O, or a sub-area within area O), which preferably includes an embedded watermark. The input device provides an output signal (e.g., representing the captured map area) to the handheld reading device  20 . Decoding software running on the handheld device  20  identifies a watermark (if present) from the signal and extracts the embedded location information from the watermark. In one embodiment, map location feedback is presented to the user via the reader device&#39;s output (e.g., an audio signal, a text display). The user is then able to compare the map coordinates to coordinates taken from a GPS receiver. 
         [0043]    In the preferred embodiment, the handheld reading device  20  includes (or is in communication with) a GPS receiver  34 . Location information is extracted from a watermark (step S 1 ,  FIG. 4 ). The current, physical location of the handheld reading device  20  is determined via the GPS receiver (Step S 2 ). In step  3 , the handheld reading device  20  compares (and/or correlates) its physical location to the map location scanned by the input device  28 . (Of course, such correlation may be realized by software computational instructions and/or with database/table look-up.). The map user is presented with appropriate corrective feedback, if needed (Step S 4 ). For example, in one embodiment, the handheld reading device  20  may prompt the user to move the input device  28  (or reading device  20 ) to a map location, which corresponds with the actual physical location of the handheld reading device  20 . (In one embodiment, the prompting is by a visual indicator (e.g., arrows or LEDs) indicating the direction in which the device must be moved. In another embodiment, an audio indication is presented, for example, such as “move six inches to the left and one inch down,” or “move to grid number E 8 .” In still another embodiment, a display screen displays a digitized replica of the map, or a portion of the map, and displays both the current physical location and the map location scanned by the input device. In still another embodiment, the output device indicates when the input device is properly located on the map with respect to the user&#39;s current physical location.). 
         [0044]    In another embodiment, the watermark&#39;s encoded data includes identification of a map&#39;s grid system. The reading device  20  correlates (e.g., via formula or table/database look-up) the grid system to the GPS coordinate system and conveys to a user her current map grid location (e.g., tells her that she is currently located in grid F- 9 ). 
         [0045]    Consider the following examples to even further illustrate the many possible applications of the present invention. 
         [0046]    A map user is examining a map of the Western United States of America while personally (e.g., physically) being located in Boise, Id. The map user places the input device  28  so as to scan a location near Tualatin, Oreg. The handheld reading device  20  can convey (e.g., via the output device  30 ) to the user to move the input device  28  East and South, until the input device  28  corresponds with the user&#39;s physical location in Boise. (GPS coordinates can help to facilitate such functionality.). In this way, the user can identify her present location with respect to the map. Alternatively, as in another embodiment, the output device  30  can indicate that the user must travel West and North to reach the scanned location near Tualatin. In still a further alternative, particularly if an index or code is embedded in the watermark, additional data can be provided to the user. To illustrate, the index is used to interrogate a networked (or local) database. Information, e.g., directions, preferred routes or roads, mileage between the current physical location and the scanned location, dining or tourist information, etc., is provided to the handheld reading device for presentation to the user. 
         [0047]    As a further example, a user is going on a trip and obtains watermarked maps (e.g., from a store, service provider, etc.). The maps are indexed by a MAP ID in a database, which can receive current information (e.g., promotions) from hotels, resorts, restaurants etc. The information can be downloaded, streamed, or stored in media (e.g., CD-ROM, electronic or magnetic media, etc.). The database may be maintained by the handheld reading device or may simply be queried via a communication channel. As the user travels, she can place her handheld reading device over various spots on the map to extract corresponding watermarks. The watermarks are then used to index the database to retrieve the downloaded information regarding hotels, resorts, etc. Hence, the watermarked map provides the user with information for places on the map just by passing the handheld reading device  20  over the map. (In contrast, database-linked GPS systems typically require the user to be in a particular location to get such information about that location.). In another example, a user enters (e.g., alphanumerical values via keypad entry or scanning the area on the watermarked map) a map location of a desired destination. The reading device determines the present location (e.g., via a GPS receiver) and provides feedback to the user. In one embodiment, the feedback is a visual indication (e.g., arrows, LEDs, text directions, grid map coordinates, visual display, etc.) of how to move the handheld device to locate the destination point, from the current location. In another embodiment, the feedback is a print out (or display) of travel directions (or map grid numbers) from the current location to the scanned, destination location. In another embodiment, the handheld device includes a known laser pointer and sensing array. Once the destination location is selected, the laser pointer points (e.g., traces) a direction from the current location to the scanned, destination location, based on the positioning of the pointer as determined by the sensing array. 
         [0048]    Now consider a potential life-saving example in which a hiker becomes lost in the mountains. The hiker presents a watermarked map to her handheld reading device  20 . 
         [0049]    The associated input device  28  scans a location on the map. The reading device then gives feedback (e.g., audio, visual, text, etc.) to the hiker to reposition the input device  28  (or the reading device  20 ) on the map to correspond with her present physical location with respect to the mountains. The hiker can then immediately identify where she is with respect to the map. (Of course, the handheld reading device  20  may include compass-like functionality, common in some GPS receivers. Such functionality is helpful to orient a map with respect to physical surroundings, e.g., to align the map&#39;s N/S reference orientation with the environmental conditions.). 
       Embedding Map Boundaries 
       [0050]    A watermark may also include (or reference) information regarding the map within which it is embedded. For example, the watermark may include a range (or boundaries) of coordinates, which define the map  10 . The handheld reading device  20  may then determine (e.g., calculate based on the GPS coordinates or via a table look-up) if the user&#39;s present, GPS-determined location is viewable on the map  10 . The user can be prompted by the device  20  to change maps when her present location is not viewable on the scanned map. In some cases, the handheld reading device may prompt (e.g., via an audible signal, text or graphic, etc.) the user to scan a specific map. This functionality is realized particularly well with the aid of additional information, such as that stored in a database. For example an atlas or an interconnected series of maps can be stored according to their corresponding coordinates (or a range of coordinates). When the watermark index does not match the present physical location (or fails to fall within the boundaries of the map), the user is prompted to select another map. If a particular set of maps is pre-programmed, e.g., preloaded onto the device, stored via CD, or via a specific on-line database, an appropriate map ID or map number (or even map name) corresponding to the scanned coordinates can be presented to the user. 
       Road Signs and Tourist Information 
       [0051]    Street (or road) signs may also be digitally watermarked as discussed above with respect to objects. Consider the implications of such. An automobile is equipped with a watermark decoder (e.g., an input device such as an optical reader, digital camera, laser reader, etc. and watermark detecting and decoding software). In one embodiment, the input device is configured with magnification enhancements, such as a zoom lens, signal amplifier, etc., to allow capture of road sign images from a far. The captured images (or corresponding signals) are input for analysis by the decoding software. The watermark payload is used to convey related information. 
         [0052]    For example, a speed limit sign may include a watermark having a corresponding speed message embedded therein. For example, upon decoding the watermark, the read device  20  signals (or itself enables) an audio message to announce the speed limit. To achieve such functionality, the payload may include an index that is used to retrieve an audio or wave file. The wave file could be played via a media player (and output device, e.g., car stereo system), or passed through a digital-to-analog converter and piped through the car&#39;s stereo system. Alternatively, the payload itself may include enough information to be converted into an audio message. 
         [0053]    In another example, the watermark includes an index that is used to interrogate a database. The database may be stored locally in the automobile, or may be accessed via a wireless network. A corresponding data record is found and returned. The returned data record may include a wide variety of information and data. To illustrate, the return information may include data about upcoming rest stops, tourist attractions, motels (and vacancy in such), speed limits, restaurants, location data, etc. A mobile traveler, upon receipt of such information, may even make a reservation at a motel via a link provided in the return information. 
         [0054]    Consider also watermarking tourist, restaurant, convenience and regulatory signs. These too can be embedded with plural-bit data. A compliant reader extracts embedded information to facilitate the retrieval of additional data regarding the sign. (The term “compliant” in this context implies that the device is able to detect and decode watermarks.). An embedded index or identifier is communicated to a database to index related information (e.g., the database may be maintained in a CD-ROM, electronic or magnetic memory residing locally in the automobile, or may be an on-line database accessed via a wireless connection. In an online database embodiment, a web browser may be installed on a compliant device, e.g., a general purpose computer, to help handle the transfer of information, e.g., HTML code, wave files, data files, etc.). Upon receipt of the related data, a traveler may access related data such as menus and prices of local restaurants, vacancies, gas prices, hours of operation, directions and maps, local attractions, etc., etc. (The functionality and systems for linking an identifier to additional data is even further described in assignee&#39;s U.S. patent application Ser. No. 09/571,422, filed May 15, 2000, now U.S. Pat. No. 6,947,571.). 
         [0055]    Signs at (or maps and photographs of) theme parks, sporting stadiums, concert halls, event centers, convention centers, zoos, office buildings, government buildings, manufacturing plants, universities, shopping malls, parks, schools, museums, etc., etc., may be similarly digitally watermarked. A handheld reading device may be used to coordinate a participant&#39;s location with respect to a map and to gather related information as discussed above. 
       Conclusion 
       [0056]    The foregoing are just exemplary implementations of navigational aids using digital watermarking technology. It will be recognized that there are a great number of variations on these basic themes. The foregoing illustrates but a few applications of the detailed technology. There are many others. 
         [0057]    While this application discusses a handheld reading device, the present invention is not so limited. Of course, an input device may be tethered to a desktop or laptop computer or compliant kiosk. The input device may also communicate with the computer via a wireless channel. 
         [0058]    To provide a comprehensive disclosure without unduly lengthening this specification, the above-mentioned patents and patent applications are hereby incorporated by reference. The particular combinations of elements and features in the above-detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this application and the incorporated-by-reference patents/applications are also contemplated. 
         [0059]    The above-described methods and functionality can be facilitated with computer executable software stored on computer readable mediums, such as electronic memory circuits, RAM, ROM, magnetic media, optical media, removable media, etc. Such software may be stored on a handheld reading device. 
         [0060]    The section headings in this application (e.g., “Watermark Reading Device”) are provided merely for the reader&#39;s convenience, and provide no substantive limitations. Of course, the disclosure under one section heading may be readily combined with the disclosure in that of another heading. 
         [0061]    As an alternative, a handheld device (or an input device) may scan a map area to capture embedded data. The handheld device wirelessly communicates the captured data to a networked computer. The computer decodes the captured data (e.g., data including a watermark). The computer can then access networked information via the decoded watermark. The data can be wirelessly communicated to the handheld device for display or may even be communicated to a separated device for display. 
         [0062]    Also, whereas the figures illustrate the map areas as rectangular-shaped, the invention is not so limited. Indeed, other area shapes may be advantageously employed. As a further alternative, individual map locations are watermarked, instead of watermarking individual blocks. For example, on a state map, all city locations are watermarked according to respective locations. In a city, streets and building locations are watermarked. In another example, areas corresponding to roads, streams, attractions can also be watermarked. 
         [0063]    In view of the wide variety of embodiments to which the principles and features discussed above can be applied, it should be apparent that the detailed embodiments are illustrative only and should not be taken as limiting the scope of the invention. Rather, we claim as our invention all such modifications as may come within the scope and spirit of the following claims and equivalents thereof.