Patent Publication Number: US-2005140544-A1

Title: Wireless handheld portable navigation system and method for visually impaired pedestrians

Description:
RELATED APPLICATIONS  
      The present application is a continuation-in-part of U.S. patent application Ser. No. 10/391,604 filed on Mar. 20, 2003. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to a wireless handheld portable navigation system and method for visually impaired pedestrians.  
     BACKGROUND OF THE INVENTION  
      Visually impaired persons must rely on external devices to be able to navigate and to carry about their business. Traditionally, white canes and guide dogs have, and continue to, serve their purpose.  
      In order to provide increased autonomy to visually impaired persons, it has been proposed to provide more automated systems, which could provide more contextual information. With the advent of the Global Positioning System of satellites, technology may take advantage of this system and attempt to provide a GPS-based navigation system. The Global Positioning System (GPS) is a navigation system that is composed of satellites turning around the earth. These satellites send signals, which are sent to the GPS receiver. It takes a minimum of three satellites in order to be able to compute a position. The more satellites are available and the better they are positioned in the sky, the better is the accuracy. But in an urban canyon (tall buildings) or in streets that are very narrow, accuracy problems or even signal coverage problems will prevent the user from receiving accurate positioning information.  
      Two prior art systems addressing the need for a GPS based navigation system are known in the art: U.S. Pat. No. 5,470,233 (Fruchterman) and U.S. Pat. No. 6,502,032 (Newman). While the systems described in these patents disclose adequate solutions, they both lack characteristics that would sustain a large endorsement by the visually impaired community.  
      The first missing characteristic is portability. To be useful to visually impaired people, a navigation system has to be highly portable. By portability, we mean a reduced weight and non bulky device. The device disclosed in the Fruchterman patent refers to a notebook computer based on an Intel 80486 CPU. At the time of that invention, a packsack was required to carry the notebook computer and the GPS receiver. Even today, with the latest developments in notebook computers, a bag or a carrying case is still needed to carry them. Newman&#39;s invention is a reduced weight device but it is still a bulky device: the system, equipped with a large Braille display and a Braille keyboard is cumbersome to wear.  
      The second missing characteristic in prior art systems is the universality. By this, we mean that a user should be able to power up his navigation system anywhere around the world and be able to use it. Both Fruchterman&#39;s and Newman&#39;s inventions rely on Differential GPS to improve the precision of the GPS positioning. Unfortunately, DGPS is not universal and is operated on a regional or local basis only. Furthermore, Newman&#39;s system uses the cellular network to access remote map servers. This implies specific infrastructures in each city where you want to operate the navigation systems.  
      The third missing characteristic from the previous art systems is the information return to the user in case of poor or no GPS signals available. Nothing is available to the user to either get information about his surrounding or his orientation and location which is considered a real problem. Following the user in an area where no GPS is available is therefore impossible with the previous systems. Relying on GPS signals only is not enough for a visually impaired user.  
      The fourth missing characteristic in previous art systems is ease of use while walking. Fruchterman&#39;s invention uses a standard 17-key, IBM-type keypad that is attached with an extension connector to the laptop computer. Newman&#39;s invention comes with a handle, a Braille keyboard and a Braille display. In both inventions, the user needs his two hands to effectively manipulate the navigation system.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a wireless, handheld portable navigation system for visually impaired pedestrians which is portable, universal, provides information to a user even in the case where a GPS signal is poor or unavailable and is easy to use while walking.  
      In accordance with the invention, this object is achieved with a wireless handheld portable navigation system for visually impaired pedestrians, comprising: a GPS receiver; a dead reckoning unit; a storage system for storing information related to spatial coordinates; a digital camera for image capture; power means for powering said wireless navigation system; a handheld computing platform operatively associated with said GPS receiver, said dead reckoning unit and with said storage system for calculating a precise user position, speed and orientation on a street segment and for guiding the user on a predefined route, said handheld computing platform being further operatively connected to said digital camera; and input and output means to enter information into said system and to receive information from said system.  
      In accordance with another aspect of the present invention, there is also provided a method for a portable positioning device to accurately determine the location of a user travelling near a road intersection where a plurality of road segments meet, said method comprising the steps of: 
          a) periodically obtaining positioning data for said user from a satellite-based positioning system;     b) mapping each of said positioning data to a mapped point on a digital road map including said road segments; and     c) when the user gets within a predetermined distance of the road intersection: 
            i. associating a candidate road segment from said plurality of road segments with each mapped point;     ii. assigning a weight to each of said mapped points;     iii. electing one of said candidate road segments upon the weights of all the mapped points associated therewith adding up to a predetermined value, thereby accurately locating the user on said elected road segment.    
               

      Other features and advantages of the present invention will be better understood upon reading of preferred embodiments thereof with reference to the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will be better understood after reading a description of a preferred embodiment thereof made in reference to the following drawings in which:  
       FIG. 1  is a schematic representation of the system of the present invention according to a preferred embodiment thereof;  
       FIG. 2  is a schematic representation of the vertical hip bounce of a user while walking;  
       FIG. 3  is a schematic representation of the change in direction of a user as determined by a gyroscope, using 4-bit encoding;  
       FIG. 4  is a schematic representation of the input commands or shortcuts used with the personal digital assistant, according to a preferred embodiment;  
      FIGS.  5  to  7  are schematic representations of the Braille cell according to a preferred embodiment of the invention for persons entering Braille dots using two thumbs; using their left thumb and commands using the right thumb; and using their right thumb and commands using their left thumb, respectively; and  
       FIG. 8  is a table describing the Braille table used by the system.  
       FIG. 9  (PRIOR ART) is a schematic illustration of the mapping accuracy difficulties at intersections of GPS-based systems.  
       FIG. 10  is a schematic illustration of a positioning strategy at an intersection where the user is going straight ahead.  
       FIG. 11  is a schematic illustration of a positioning strategy at an intersection where the user is turning left. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION  
      The present invention relates to a system  10  for orienting and guiding visually impaired pedestrians. The system combines a Global Positioning System (GPS) receiver  17  to a dead reckoning unit (DRU)  15  that compensates for GPS imprecision and loss of signal in order to improve the accuracy of the system  10 . The system  10  also uses wireless protocols such as IEEE 802.11b, to receive additional orientation information from a remote location server or operator through the Internet. As shown in  FIG. 1 , the system is highly portable: it is based on a handheld portable computing platform  30 , such as a Personal Digital Assistant (PDA), that communicates wirelessly with a self-powered strap  20  containing the GPS receiver  17  and the DRU  15 . In a preferred embodiment of the invention, the strap is worn by the user around the neck or a shoulder, in order to provide line-of-sight positioning for the GPS receiver.  
      To compensate for GPS imprecision and loss of signal, the present invention relies on a built-in dead reckoning unit  15 . The unit fills the gaps between the loss and reacquiring of the GPS signal. Consequently, the system can at any time interrogate the system to get information with respect to the real or estimated position.  
      The present invention is an orientation aid that uses the Global Positioning System (GPS) and digital maps to help visually impaired persons find their way in urban and rural areas. With this invention, users can pinpoint exactly where they are, and learn about area attractions. GPS lets users know their location, anywhere in the world, with continually growing precision.  
      The present invention offers visually impaired persons greater freedom, raising their confidence in their ability to travel near or far, for business or pleasure. It also helps them access and enjoy the most valuable and interesting opportunities their surroundings have to offer. The present invention contributes to guide the visually impaired through their environment. It complements existing aids (white canes and guide dogs) without, however, replacing them.  
      This invention advantageously provides information in the most natural way possible and allows users to record both vocal and written notes.  
      The system of the present invention also uses wireless protocols to receive additional information from a remote location server or operator, accessible through the internet.  
      With the system of the present invention, a user can interact with the system using only one hand. This is an important advantage of the system of the present invention, because visually impaired persons generally only have one hand available when walking: visually impaired persons generally use a white cane or a guide dog.  
      Further advantageously, the system of the present invention maps a specific function to each of the five PDA control buttons. Furthermore, the present invention enables the user to use the PDA navigation button (up, down, right and left arrows), to have access to the overall menu of the software application running on the PDA, and to perform tasks such as browsing a map while walking, or use the reading mode of the system to listen to previously recorded messages.  
      Hardware Components  
      Referring now to  FIG. 1 , the wireless handheld portable navigation system comprises a GPS receiver  17 , a dead reckoning unit  15 , a storage system for storing information related to spatial coordinates  33 , a digital camera for image capture  31 , a handheld computing platform  30  operatively associated with the above components, input and output means for entering information into the system and to receive information from the system, and power means for powering the system.  
      In a preferred embodiment, as shown in  FIG. 1 , the output means  11 , dead reckoning unit  15 , GPS receiver  17  and power means  19  are disposed in a strap  20  which is adapted to be worn by a user. The handheld computing platform  30 , digital camera  31 , storage system  33  and input means are included in a personal digital assistant, which is in wireless communication with the strap.  
      More specifically, and according to a preferred embodiment of the invention, the wireless handheld navigation system comprises the following hardware components: 
          a self-powered bluetooth strap containing a GPS receiver  17 , a dead reckoning unit  15 , an amplified speaker  11 ,  13  and a rechargeable battery pack  19 ;     a Secure Data (SD) or Compact Flash (CF) card  33  for storage of the following elements: maps and associated Points Of Interest (POI), user defined POI and user defined routes;     a Digital Camera  31  for image capture;     a wireless bluetooth and 802.11b Personal Digital Assistant (PDA)  30  that calculates a precise user position, speed and orientation on a street segment and that guides the user on a predefined route. 
 
 Self-powered Strap 
       

      The self-powered strap  20  communicates wirelessly with the PDA using the bluetooth protocol through a transceiver  21 . The wireless communication between the self-powered strap  20  and the PDA  30  increases the usability of the system. First, the user does not have to connect to the PDA a fragile connector that was not designed to be used by visually impaired people. Second, if the user does not have to interact with the PDA while walking and using the system, he can put the PDA aside in a coat pocket or clip it to his belt: he will still receive audio messages as he walks along the streets. Also, if the user wants to interact with the PDA while walking, he can easily manipulate the PDA using only one hand which leaves him a free hand for a white cane or a dog.  
      Duplex communication takes place between the PDA and the self-powered strap. The strap sends two types of information to the PDA: positioning information coming out from the GPS receiver, and distance traveled/change in direction by the user coming out from the dead reckoning unit. The PDA sends to the self-powered strap ON/OFF signals and audio signals to be played by the strap speaker.  
      Dead Reckoning Unit  
      A dead reckoning unit (DRU)  15  is part of the system and was designed to compensate for GPS imprecision and loss of signal. The DRU comprises three main components: an accelerometer, a gyroscope and a micro controller.  
      The DRU provides to the system the distance walked by the user and the change in direction by the user. Using these two measures combined to a digital map, the system is able to follow the user&#39;s path on street segments even if a loss of GPS signal occurs.  
      Measure of the Distance Walked By the User  
      As shown in  FIG. 2 , a vertical bounce occurs in the user hip at each step the user makes while walking. The measure of the distance traveled by the user is estimated from these vertical bounces.  
      The DRU sends to the system two parameters: 
          Walking state (WALKING or NOT_WALKING) (1 bit)     Number of steps (typically transmitted at each second) (4 bits)        

      The walking state is determined using one accelerometer that detects the vertical bounces that occur at the hip while the user is walking. A pass band filter is used to filter vertical bounces from interference bounces generated by arm movements or rotational movements.  
      If the user is walking, the system calculates the distance traveled by the user between two points by multiplying the number of steps by the average distance of a user step (the average distance of a step is calculated by dividing the distance between 2 precise GPS positions by the number of steps that have occurred between these 2 positions).  
      Measure of the Chance in Direction By the User  
      Relative direction of the user is determined from a gyroscope. The gyroscope was chosen because of its precision and because it is not affected by the presence of metallic masses or magnetic fields. However, the present invention is not limited to using a gyroscope or even an accelerometer. Other components which can provide an estimation of the distance traveled by a user and a change in the direction of travel in order to form a dead reckoning unit falls within the scope of the present invention.  
      The output of a gyroscope is an instantaneous angular velocity (number of degrees per second). The number of degrees covered is obtained by integrating the instantaneous angular velocity over one second. For example, if the user turns 90 degrees clockwise in one second, the DRU will transmit the value 90 degrees to the system.  
      As shown in  FIG. 3 , change in relative direction is encoded using 4 bits for a resolution of 22.5 degrees.  
      Accessible Handheld Computing Platform  
      PDA&#39;s Button Interface  
      Parts of the PDA had to be adapted for the blind or those with low vision in order to let them easily interact with the system of the present invention. As shown in  FIG. 4 , the buttons  39 ,  41 ,  43 ,  45 ,  47 ,  49 ,  37  of the front panel and the side panel of the PDA were adapted to be used as input commands or shortcuts to the system. Four buttons  41 ,  43 ,  49 ,  37  and a navigation button  45  are available on the front panel. The ‘Where Am I’ function is mapped to one of the four buttons, as well as the stop speech, the Reading/Browsing mode and the menu access. The side panel button  39  is used as a shortcut to create a point of interest via a voice recording. By pressing the button, the user records a significant message related to the point of interest that he wishes to create, like the name of the point of interest, or other meaningful information. The navigation button is used to navigate the menu or to virtually browse the map.  
      Voice Command Input  
      Using the PDA&#39;s microphone and an off-the-shelf speech recognition engine, users can also interact with the system using the voice command. The system takes as input the voice of the user and if a pattern is recognized, the associated command is performed.  
      Touch Screen Input  
      The touch screen of the PDA is also used as another way to exchange information with the system. Touching the screen at specific places may input text to the system or invoke specific commands. However, it has been discovered that a tactile keyboard is an important advantage of the present invention in order to enable a user to enter information, as will be seen hereinafter.  
      Tactile Keyboard  
      A tactile keyboard representation is preferably used when inputting text to the system. A Braille cell  101 ,  101 ′,  102 ″, or telephone keyboard representation over the touch screen, is the tactile implementation that is preferred in the context of the present invention. The touch screen of the PDA is pressed at a specific location, to reproduce input of the corresponding character via, either the combination required by the Braille alphabet, or a telephone keyboard press.  
      Touch Screen Braille Cell  
      As shown in  FIG. 5 , the screen is divided like a Braille cell, which makes it easy for a Braille user to enter text. The screen is divided into twelve equal squares, four rows and three columns, representing 12 dots. The side columns represent a Braille cell (matrix of 2×4 dots).  
      The Braille table used by the system is described in  FIG. 8 . The first column of the screen is numbered row  1 : DOT  1 , row  2 : DOT  2 , row  3 : DOT  3 , row  4 : DOT  7 . The third column is numbered row  1 : DOT  4 , row  2 : DOT  5 , row  3 : DOT  6 , row  4 : DOT  8 . For example, to enter the letter ‘A’, the user needs to press DOT  1  and DOT  7 . When a dot is pressed, it stays down until the character is either accepted or cancelled. This enables a user to press each dot separately with only one or two fingers.  
      The middle column of the screen is used as a command column. The first dot of the middle column, at the top, is the Accept command. This is used to accept that the entered character is appended to the current string. The second dot of the middle column is the Space command. This is used to append a space to the current string. The third dot of the middle column is the Backspace command. It cancels the current configuration of the cell, if there is one, or deletes the previous character if no configuration is pending. The fourth and last item of the middle column has no function for the moment.  
      To enter a character, the user taps on the screen in the appropriate spaces, and the corresponding character is heard. The user than accepts the character to append it to the current string, or cancels the operation and redoes the tapping. The Braille Cell interface requires a certain degree of training in order to learn to place the thumbs in the right place. It is suggested to take the PDA in both hands, and reach for the screen with both thumbs for faster input.  
      The disposition of the Braille dots/command dots can be set by the user. There are 3 available configurations: 
      1. Designed for people who enter Braille Dots using their  2  thumbs (see  FIG. 5 )     2. Designed for people who enter Braille Dots using their left thumb and commands using their right thumb (see  FIG. 6 )     3. Designed for people who enter Braille Dots using their right thumb and commands using their left thumb (see  FIG. 7 )    

      The Braille Cell can also be configured with 6 or 8 dots (instead of 12). When set in 6 or 8 dots mode, this Braille cell is used only to type in Braille characters. A user presses the dots on the screen to form a Braille Character and presses a button on the PDA when the character configuration is completed.  
      Touch Telephone Keypad  
      The screen is divided like a telephone keyboard, which makes it easy for people, who are not Braille users, to enter text. The screen is divided into twelve equal squares—four rows and three columns. The following representation of the telephone keyboard is used:  
                                                          1   2, A, B, C   3, D, E, F           4, G, H, I   5, J, K, L   6, M, N, O           7, P, Q, R   8, S, T, U   9, V, W, X           *   0, Y, Z   #                      
 
      Ten digits plus the NUMBER sign and the STAR are represented. To each digit of this Touch Telephone Keypad are associated several letters. The user presses on a digit until the desired letter is found (heard). When the letter is found, the user presses a button of the PDA to add it in the text string.  
      Plastic Molded Membrane for the Input Adapted Keyboard  
      A thin plastic membrane molded as a Braille cell, or telephone keyboard, as described in the previous section, is in twelve sections equally divided. This membrane is put over the touch screen of the PDA, to serve as delimiter for the input adapted keyboard.  
      Speaker Output  
      The system gives audio information to the user via the PDA&#39;s speaker but also via the speaker  11  located on the strap. When the user is in an urban environment, cars and other vehicles make a lot of noise. The PDA&#39;s speaker is not enough for the user to hear clearly what the system is telling him, therefore, the use of a speaker is required.  
      User Interface  
      The following section details the advancements to the previous art system described in U.S. Pat. No. 5,470,233 issued to Fruchterman et al., and their related advantages.  
      It is imperative that the user knows in which type of GPS reception he is, in order to better estimate his chances of accurately orienting himself, at any moment. Therefore, we have conceived a specific GPS interface which is comprised of: 
          a. Verbal information to the user, upon request, on the quality of the GPS signal reception. The following reception status are given to the user: No Coverage, Poor Coverage, Good Coverage.     b. A tone, upon passing from a poor or good GPS reception to No Coverage is heard automatically, when the GPS signal has been lost for some time. This way, the user is informed that at the given time, a certain functionality of the system is not working.     c. Upon user&#39;s request, it is possible for him to know, at any moment, what type of accuracy he can expect of the system. An estimation, in feet or meters, of the radius of precision regarding his position is given. The user may then make a better estimation of his orientation at that specific moment.     d. The user has access to physical system information regarding the battery level given as a percentage, the map information such as the name of the loaded map, its version, the storage left on the device, which is the SD or CF card, help the user to make decisions regarding the creation of points of interests, or cleaning he has to make in order to add space for further input to the system.     e. Searching information in the points of interest database, with search filters such as POI category, POI name or address is very useful to the user, in order to easily find a telephone, or change a specific information about this POI.     f. Activation or deactivation of a POI is available to the user so that specific POIs can no longer be detected or can be detected again when the user is crossing their location. Unlike the deletion of a POI, all the information is kept, but no longer referred to, except when you activate it again.     g. Favorite attribute can be associated to a POI, in order to improve search performances or select browsing origin easier.     h. When the user, for any reason, did not hear the information given by the system, it is possible for him to get this information back. A Reading Mode is provided to the user, in order to listen to previous messages. The user only has to touch the up arrow, and the system will go through, line by line, all the previous messages available.     i. When the user is in an area that covers many points of interest, a commercial center for example, it would be very inconvenient for the user to hear all of the boutiques information comprised in this zone. We have decided to make them available to the user via a list in a dialog box, after detecting some three different POIs in a small area.     j. Creation of a POI, while outside can be very demanding if you have to enter text in the middle of a street. Using the recording of voice, and creating at the same time a POI, with a default name, is somewhat easier. The user presses a button, and talks to the microphone, giving strategic information in order to recognize it later.     k. Creating a POI while virtually browsing the map is important so that the user does not necessarily have to go outside in order to create a POI. The user enters the browsing mode, goes to the desired position and creates a POI with the same recording/poi creation button.     l. Creating a route while virtually browsing the map is also important so that the user does not necessarily have to go outside in order to create a route. The user may create a bread crumb route, or enter a specific address as origin and destination, or a POI as origin or destination, and the system computes a route for the user. If an address is given, an estimated position (latitude and longitude) of the address is computed.     m. When the user is executing a route, meaning he is being guided through a route, it is possible for him to hit the reverse button of the PDA, which automatically reverses the route from the current position, and guides the user back to his origin.     n. Tunnel detection mode: detection of points of interest, while the user moves, can be done in a tunnel mode, detecting only the POIs that are located in a virtual tunnel, according to the user&#39;s heading.     o. Different voices to create a stereo effect: detection of a point of interest takes into account its relative position to the user, if the POI is located at the user&#39;s left, the user will hear a certain voice attributed to the left side, another voice is used when detection occurs at the right side. 
 
 Positioning Algorithm 
       

      The handheld computing platform also preferably includes a positioning algorithm which preferably allows to accurately determine the location of a user traveling near a road intersection.  
      Positioning a pedestrian on a digital map, using only GPS-like systems does have its limitations. Those limitations are mainly due to the GPS signal&#39;s lack of precision. In accordance with another aspect of the present invention, there is therefore provided a positioning algorithm for accurately determining the location of a user travelling near a road intersection. The method of this algorithm solves the accuracy problem regarding such applications.  
      When the pedestrian, walking on a street, comes closer to an intersection, the GPS system is not accurate enough to give the right positioning information. Most likely, the pedestrian will be mapped to one of the lateral streets that composes the intersection. This information is not the right position of the pedestrian. To alleviate this drawback, an intersection zone is preferably created, which coupled with the right mapping algorithm, does not map the user to those lateral segments, unless the person is deduced to be turning. This way, the user gets the right information as soon as the mapping reaches a certain stability, whether the user has turned at the intersection, or not.  
      In a system that wishes to have the best estimated position, some assumptions must be made. The person is preferably presumed to be walking on the street and not on a path along the street. The application is using GPS or GNSS for positioning, and a digital map is being used to map the user on the street.  
      Each street is represented on the digital map as road segments, or in other words, a segment on the map represents an element of the road network, on which a pedestrian is walking. Most of the time, it represents a part of a street. It is composed of two georeferenced positions, in latitude and longitude.  
      The algorithm preferably performs the following steps: 
          a) periodically obtaining positioning data for the user from a satellite-based positioning system such as a GPS or GNSS;     b) mapping each of this positioning data to a mapped point on a digital road map including road segments; and     c) when the user gets within a predetermined distance of the road intersection: 
            i. associating a candidate road segment with each mapped point;     ii. assigning a weight to each mapped points;     iii. electing one of the candidate road segments upon the weights of all the mapped points associated therewith adding up to a predetermined value, thereby accurately locating the user on the elected road segment.    
               

      By “mapping” it is understood the action of taking a GPS position and projecting it on a digital map, to a street segment. A mapped position is a GPS position that has been projected to the closest street segment.  
      Referring to FIGS.  9  to  11 , the segment where the pedestrian is currently mapped is identified as the “current segment”. A candidate segment is a segment on which GPS positions have been mapped to, but it has not been declared as the current one. The elected segment is the new current segment which has just replaced the preceding current segment.  
      The positioning strategy is preferably as follows. A GPS position is received by the GPS receiver. The application or algorithm that treats this position finds the closest segment to the position. If this segment is the current segment, add the point to it. If it is a candidate segment, add the point to this candidate segment. If the segment is not present in the candidate segment list, add it to the list and add the point to it.  
      A segment is elected as the current segment when one of the candidate segments reaches a certain amount of points mapped.  
      Upon a new current segment election, the former current segment is referred to as the preceding current segment, and all the candidate segments are forgotten.  
      The GPS precision problems are unveiled by the fact that at some point, at the intersection, the pedestrian gets mapped regularly to the crossing street, while in fact, he is still on the same street segment.  
      The way to alleviate to this is to declare an intersection zone which defines a certain circle around this intersection.  
      When a point is mapped within a certain distance from the intersection, all the segments composing the intersection have to be retrieved and are kept as candidate segments.  
      Upon mapping a GPS position to a candidate segment of the intersection, weight is given to each of the points. In the preferred embodiment, the weight is proportional to the distance between the mapped position and the center of the intersection. The farther to the intersection the point on the segment is, the more this point gets an increased weight. Each candidate segment of the intersection keeps a weight controller. When one of the candidate segments reaches a certain weight, this segment becomes the new current segment. The pedestrian is then considered as he has left the intersection zone.  
      The positioning algorithm may additionally include a number of optional features as follows:  
      Advantageously, any sudden position that is more than a certain distance of a candidate segment, is rejected from the mapping algorithm to the map. When a certain amount of positions are subsequently getting away from the current segment, the pedestrian is considered to be out of the road mapping system.  
      When the pedestrian stops, the GPS relates the speed of the user as being zero. The positions for which a speed of zero is detected are rejected from the mapping algorithm.  
      At any moment, if the GPS fails to give a decent signal, for a certain time, a re-initialization process takes place, clearing all the candidate segments and current segment. Upon proper GPS signal reception, the mapping process is restarted.  
      Wireless Communication With the Internet  
      The present invention uses wireless protocols, such as IEEE 802.11b, to connect to the internet and to download up to date information. IEEE 802.11b protocol, commonly known as WI-FI, is gaining popularity in the office and at home. Moreover, multiple WI-FI public-access networks are under development in the United States, in the U.K. and in other countries.  
      The present invention integrates the WI-FI protocols and enables the user to easily download up to date map data from a remote map server.  
      The present invention also enables the user, while walking, if WI-FI public “hot spots” are available, to download up to date information on specific Points of Interest (POI) that he is crossing (restaurant menu, opening hours of a bank, etc.).  
      The information downloaded from the internet can give valuable hints to the user about his surroundings and/or information about buildings and their functions, for example: how to get to the metro station from where he stands, how to go by in the station, or any other information that adds to the orientation of the user. The user may use this information for further reference. Tourist information can also be downloaded as well as predefined routes for the user. Any useful information to the user can be downloaded from the internet.  
      Image Analysis  
      The present navigation system supports image analysis that is used by visually impaired pedestrians to increase their orientation and surrounding knowledge.  
      Image analysis is used for tasks such as: locating the entrance of a building and guiding the user to that entrance; identifying objects or signs encountered by the user while walking; provide the user with indoor guiding instructions; providing the user with outdoor guiding instructions if the GPS signal is not available.  
      The visually impaired pedestrians use the system digital camera to grab still images that are automatically transferred, through WI-FI internet, to a remote image server or operator. Still images are transferred to the remote image server/operator using the file transfer protocol (ftp).  
      The still images are analyzed by the remote image server/operator. Results of image analysis are produced in text format and sent back to the navigation system. The system then converts the textual information into speech.  
      Although the present invention has been explained hereinabove by way of a preferred embodiment thereof, it should be pointed out that any modifications to this preferred embodiment within the scope of the appended claims is not deemed to alter or change the nature and scope of the present invention.