Client-server based remote locator device

What is claimed is:

1. A computer implemented method of determining the location of a mobile remote sensor, the method comprising the steps of:

accessing a server using a client, said client being remote from said server;

providing an identification code from said client to said server, said identification code uniquely associated with said remote sensor;

interrogating said remote sensor from said server based on said identification code;

transmitting positioning data from said remote sensor to said server in response to said step of interrogating;

analyzing said positioning data at said server to produce processed positioning information, said processed positioning information representing the location of said remote sensor;

transmitting said processed positioning information from said server to said client; and

displaying said processed positioning information at said client so that a user can identify the location of said remote sensor.

2. The computer implemented method of claim 1 wherein said client and said server are connected to a computer network and wherein said step of accessing further comprises the step of:

using a web browser to interrogate said server, said web browser providing a graphical user interface for said user at said client.

3. The computer implemented method of claim 2 wherein said computer network is the Internet and wherein said step of accessing further comprises the step of:

providing a web page from said server to said client after said web browser interrogates said server.

4. The computer implemented method of claim 3 wherein said web page provides means for said user to identify said remote sensor and wherein said step of providing an identification code further comprises the step of:

transmitting said identification code from said client to said server using said means for said user to identify said remote sensor.

5. The computer implemented method of claim 4 wherein said server is associated with a communication station and wherein said step of interrogating said remote sensor further comprises the steps of:

receiving said identification code at said server;

identifying said remote sensor based on said identification code;

transmitting an interrogation signal to said remote sensor using said communication station.

6. The computer implemented method of claim 5 wherein said remote sensor comprises a SNAPSHOT GPS receiver and said server is further associated with a GPS base station and wherein said step of interrogating said remote sensor further comprises the step of:

transmitting from said server to said remote sensor Doppler information regarding in-view satellites using said communication station.

7. The computer implemented method of claim 5 wherein said remote sensor comprises a GPS receiver and wherein said step of transmitting positioning data further comprises the steps of:

receiving said interrogation signal at said remote sensor;

computing said positioning data at said remote sensor;

transmitting said positioning data from said remote sensor to said server.

8. The computer implemented method of claim 7 wherein said positioning data comprises pseudoranges.

9. The computer implemented method of claim 7 wherein said positioning data comprises a latitude and longitude.

10. The computer implemented method of claim 7 wherein said positioning data comprises a latitude, a longitude and an altitude.

11. The computer implemented method of claim 6 wherein said positioning data comprises pseudoranges.

12. The computer implemented method of claim 6 wherein said positioning data comprises a latitude and a longitude.

13. The computer implemented method of claim 6 wherein said positioning data comprises a latitude, a longitude and an altitude.

14. The computer implemented method of claim 7 wherein said remote sensor

comprises a SNAPSHOT GPS receiver and wherein said interrogation signal includes Doppler information regarding in-view satellites.

15. The computer implemented method of claim 7 wherein said interrogation signal includes differential GPS corrections.

16. The computer implemented method of claim 7 wherein said step of analyzing further comprises the steps of:

receiving said positioning data at said server; and

associating said positioning data with a digital map to produce said processed positioning information, said processed positioning information comprising a graphical representation of the location of said remote sensor.

17. The computer implemented method of claim 7 wherein said step of analyzing further comprises the steps of:

receiving said positioning data at said server; and

applying differential corrections to said positioning data to produce said processed positioning information.

18. The computer implemented method of claim 7 wherein said positioning data comprises pseudoranges and wherein said step of analyzing further comprises the steps of:

receiving said positioning data at said server; and

computing said processed positioning information at said server using said positioning data.

19. The computer implemented method of claim 18 wherein said step of computing said processed positioning information further comprises the step of applying differential GPS corrections to said positioning data.

20. The computer implemented method of claim 2 wherein said computer network is a private network and wherein said step of accessing further comprises the step of:

providing a web page from said server to said client after said web browser interrogates said server.

21. The computer implemented method of claim 20 wherein said web page provides means for said user to identify said remote sensor and wherein said step of providing an identification code further comprises the step of:

transmitting said identification code from said client to said server using said means for said user to identify said remote sensor.

22. The computer implemented method of claim 21 wherein said server is associated with a communication station and wherein said step of interrogating said remote sensor further comprises the steps of:

receiving said identification code at said server;

identifying said remote sensor based on said identification code;

transmitting an interrogation signal to said remote sensor using said communication station.

23. The computer implemented method of claim 22 wherein said remote sensor comprises a snapshot GPS receiver and said server is further associated with a GPS base station and wherein said step of interrogating said remote sensor further comprises the step of:

transmitting from said server to said remote sensor Doppler information regarding in-view satellites using said communication station.

24. The computer implemented method of claim 22 wherein said remote sensor comprises a GPS receiver and wherein said step of transmitting positioning data further comprises the steps of:

receiving said interrogation signal at said remote sensor;

computing said positioning data at said remote sensor;

transmitting said positioning data from said remote sensor to said server.

25. The computer implemented method of claim 24 wherein said positioning data comprises pseudoranges.

26. The computer implemented method of claim 24 wherein said positioning data comprises a latitude and longitude.

27. The computer implemented method of claim 24 wherein said positioning data comprises a latitude, a longitude and an altitude.

28. The computer implemented method of claim 23 wherein said positioning data comprises pseudoranges.

29. The computer implemented method of claim 23 wherein said positioning data comprises a latitude and a longitude.

30. The computer implemented method of claim 23 wherein said positioning data comprises a latitude, a longitude and an altitude.

31. The computer implemented method of claim 24 wherein said remote sensor comprises a SNAPSHOT GPS receiver and wherein said interrogation signal includes Doppler information regarding in-view satellites.

32. The computer implemented method of claim 24 wherein said interrogation signal includes differential GPS corrections.

33. The computer implemented method of claim 24 wherein said step of analyzing further comprises the steps of:

receiving said positioning data at said server; and

associating said positioning data with a digital map to produce said processed positioning information, said processed positioning information comprising a graphical representation of the location of said remote sensor.

34. The computer implemented method of claim 24 wherein said step of analyzing further comprises the steps of:

receiving said positioning data at said server; and

applying differential corrections to said positioning data to produce said processed positioning information.

35. The computer implemented method of claim 24 wherein said positioning data comprises pseudoranges and wherein said step of analyzing further comprises the steps of:

receiving said positioning data at said server; and

computing said processed positioning information at said server using said positioning data.

36. The computer implemented method of claim 35 wherein said step of computing said processed positioning information further comprises the step of applying differential GPS corrections to said positioning data.

37. The computer implemented method of claim 16 wherein said processed positioning information comprises a GIF format document.

38. The computer implemented method of claim 16 wherein said processed positioning information comprises a JPEG format document.

39. The computer implemented method of claim 33 wherein said processed positioning information comprises a GIF format document.

40. The computer implemented method of claim 33 wherein said processed positioning information comprises a JPEG format document.

Description Submit all comments and votes

FIELD OF THE INVENTION

The present invention concerns client-server computer networks and the use of such networks to access remote sensors having associated position determination sensors.

BACKGROUND

Networking technology has developed a large network of networks, referred to as the Internet, which interconnects millions of computers around the world. The Internet allows the transfer of data between any number of computer systems connected to the Internet using the Transmission Protocol/Internet Protocol (TCP/IP). Computers responding to service requests from other computers, via the Internet, are commonly referred to as servers, and computers that initiate requests for service from a server are referred to as clients.

The Internet has become very popular in part due to the World Wide Web (WWW), which is a network of links to hypertext documents operating within the Internet. These hypertext documents are referred to as either Web documents, Web pages, or hypertext documents. Web documents are embedded with directly accessible connections or links to other documents which create a non-linear way of reading the document. The links are embedded in Web documents as a phrase of text or an image which can be selected and activated by a computer user. Information about the Web documents are controlled and provided by Web servers. At the user's end, a Web client takes the user's requests and passes them on to the Web server. A collection of related Web documents maintained by a single company or other entity is often referred to as a Web site.

The Web documents are written with a high level programming language referred to as the Hypertext Markup Language (HTML). Commands of the HTML, popularly known as tags, provide a variety of functions including, but not limited to, defining special format and layout information in a Web document, embedding images and sound in a Web document, and embedding links to other Web documents.

In order to access, process, and display a Web document, a client uses a set of instructions, referred to as a browser. The browser typically includes a set of browser commands corresponding to the tags available in the HTML. Each browser command in turn points to a procedure of one or more instructions defining the command which, when executed, provide a functionality of the respective command. If the client requires service from the Web server, the browser uses the Hypertext Transfer Protocol (HTTP) to communicate with the server.

The browser compares each tag found embedded in a Web document with the set of browser commands. Once a match is found, the browser executes the procedure corresponding to the match browser command in order to provide the functionality of the respective command.

Recently, some Web sites have begun offering users navigation-like aids. For example, some Web sites allow users to request the location of a tourist attraction or other location (e.g., a restaurant) and provide a map or a series of directions to the location in question. Often the Web sit provider will charge a user fee for this service or instead may charge a fee to the restaurant owners and others who wish to have the location of their business, etc. accessible in this manner. In this fashion, the Internet and the World Wide Web is becoming a useful tool for locating fixed sites. What is lacking, however, is a way for a user to locate a mobile remote object using such technology.

SUMMARY

One embodiment of the present invention provides a computer implemented method of determining the location of a remote sensor. In operation, a user accesses a server using a client. The client provides an identification code which serves to uniquely identify a remote sensor. The remote sensor is capable of providing information related to its position. The server then interrogates the remote sensor which is identified based on the identification code. In response, the remote sensor transmits positioning data to the server where it is analyzed to derive the location of the remote sensor. The location so determined is transmitted from the server to the client and is displayed at the client so that the user can identify the location of the remote sensor.

In this embodiment, the client and the server may be connected to a computer network and the client may use a web browser to interrogate the server. In general, the web browser provides a graphical user interface for the user. The computer network may be the Internet, a local area network or another data communications network. Where the Internet is used, the server may provide a web page having means for the user to identify the remote sensor.

In another embodiment, the present invention provides a method of determining the location of a remote sensor wherein a position signal having positioning data and an identification code is transmitted from a remote sensor to a server. The server receives the position signal and analyzes the signal to generate information representing the location of the remote sensor. The server transmits this location information to a client where the location information is displayed, thereby allowing a user to identify the location of the remote sensor.

In this embodiment, the position signal transmitted by the remote sensor may include an emergency code. The signal may be transmitted using a modulated radio frequency carrier or other transmission media.

The remote sensor may be a SNAPSHOT GPS receiver capable of obtaining a position fix in a relatively short period of time. Other GPS receivers or positioning devices could also be used.

The user display may be a simple position report, e.g., latitude and longitude, or a graphical report which provides an indication of the remote sensor's location superimposed on a map or other reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements and in which:

FIG. 1A is a block diagram of the major components of a computer implemented system for determining the location of a remote sensor utilizing the methods of the present invention;

FIG. 1B is a block diagram of an alternate embodiment of a computer implemented system for determining the location of a remote sensor utilizing the methods of the present invention;

FIG. 2 is a block diagram illustrating one embodiment of a SNAPSHOT GPS receiver for use according to the present invention;

FIGS. 3A and 3B provide two alternatives for the RF and IF portions of a snapshot GPS receiver for use according to the present invention;

FIG. 4 shows a flowgraph of the major software operations performed by a programmable DSP processor of a snapshot GPS receiver for use according to the present invention;

FIGS. 5A-5E illustrate a signal processing waveform at various stages of processing in a snapshot GPS receiver for use according to the present invention; and

FIG. 6 is an exemplary flow diagram for the server functions according to one embodiment of the present invention.

DETAILED DESCRIPTION

This invention concerns apparatus and methods for determining the position of a mobile, or remote, object using networks operating as clients and servers. One implementation of such a computer network is shown in FIG. 1A.

FIG. 1A illustrates a user having a laptop or other computer 1 connected to a computer network such as the Internet 5. The Internet 5 is a large network of networks which interconnects millions of computers around the world. The user's computer 1 is connected to the Internet 5 via an Internet Service Provider 2. The Internet Service Provider 2 is generally a server which allows a number of remote users to connect to the Internet 5 over telephone or other communication (e.g., ISDN) links. Users establish accounts with the Internet Service Provider 2 to allow access to the Internet 5 on demand, typically through a dial-up connection. Computer 1 will be recognized as a Web client or browser.

Also connected to Internet 5 through an Internet Service Provider 3 is base station 10 which includes a server 200. Server 200 is connected to the Internet 5 via telephone lines and modem 202. In alternative embodiments, server 200 may utilize ISDN or other data communication links to connect to Internet 5. Also, server 200 may be directly connected to Internet 5, without the need for Internet Service Provider 3.

Server 200 will be recognized as a Web Server. As such, it provides hypertext or Web documents which can be accessed by computer 1. These Web documents may be accessed directly through an Internet address associated with server 200 or by following links embedded in other Web documents as a phrase of text or an image which can be selected and activated by a computer user.

At the user's end, computer 1 includes a browser in order to access, process, and display Web documents. If the user requires service from server 200, the browser uses the Hypertext Transfer Protocol (HTTP) or other suitable protocol to communicate with the server 200 over Internet 5 as described above.

In addition to server 200, base station 10 includes a GPS receiver 204 with an associated GPS antenna 212. GPS receiver 204 is a conventional GPS receiver capable of determining exact GPS time from in-view satellites. GPS receiver 204 provides current GPS time to server 200 and also provides a one pulse per second signal to Time Trigger 210 as described below.

In one embodiment, the location of GPS antenna 212 may be precisely determined using a survey or other means. Then, position information provided by GPS receiver 204 can be compared against the known location of GPS antenna 212 to produce position correction information at base station 10. These position corrections can be applied to pseudoranges as Differential GPS (DGPS) corrections in order to precisely determine the location of GPS antenna 212 as is known in the art. As will be apparent upon review of this specification, however, the location of server 200 is not critical.

Base station 10 also includes a connection (e.g., modem 214) to a cellular telephone transmitter site (cell site) 208. Modem 214 is connected to server 200 to allow a telephone line connection to the cell site 208. In other embodiments, an ISDN or other data communications link may be used. Time Trigger 210 is also connected to the communications link to cell site 208 and is under the control of server 200. Time Trigger 210 provides a means of indicating time to a remote sensor 20 as described below. Cell site 208 has an associated antenna 214 which allows two-way communication with remote sensor 20.

Remote sensor 20 includes a conventional cellular telephone 222 which is connected to a SNAPSHOT GPS receiver 220 and a time trigger 224. The SNAPSHOT GPS receiver 220 is described in detail below. Briefly, SNAPSHOT GPS receiver 220 responds to commands from server 200, which are transmitted across the cellular communication link provided by cell site 208 and cell phone 222, to take a position fix using in-view GPS satellites. As described more fully below, the command from server 200 may also include Doppler prediction data regarding each of the in-view satellites. The Doppler information is collected by server 200 using GPS receiver 204. This Doppler information allows SNAPSHOT GPS receiver 220 to obtain rapid position fixes as it eliminates the Doppler uncertainty those skilled in the art will appreciate in inherent in all GPS position calculations. Cellular telephone 222 may include a modem or other communication device appropriate for the method of data transmission used. Time trigger 224 provides means of identifying an accurate time stamp for a snapshot of data taken by SNAPSHOT GPS receiver 220.

The command from server 200 may include a time trigger signal which provides the remote sensor 20 with an indication of the time. For example, sensor 200 may transmit a message which indicates that "at the tone, the time will be `x`". This message is then followed by a tone generated by time trigger 210 in response to a control signal from server 200. Of course, other time trigger signals may also be used. Notice that time trigger 210 is connected to GPS receiver 204. Those skilled in the art will appreciate that GPS receivers such as GPS receiver 204 are capable of providing a very accurate timing reference output, for example, one pulse per second or fraction thereof. If such a timing reference signal is applied to time trigger 210, say once per second, then time trigger 210 will generate a time trigger output signal once per second on a stable basis when enabled by server 200 through a control signal. When time trigger 210 then receives a control signal from server 200 indicating that the time trigger signal is to be transmitted to remote sensor 20, the next time trigger signal generated (i.e., at the next one second interval as clocked by the output of GPS receiver 204) will be transmitted via cell size 208 to remote sensor 20.

Remote sensor 20 is able to use the received time trigger signal as the basis for initiating the collection of satellite data as described in detail below. Remote sensor 20 can then compute pseudoranges from the collected satellite data using SNAPSHOT GPS receiver 220 as described in detail below.

When SNAPSHOT GPS receiver 220 has obtained pseudoranges to the in-view satellites, this information is transmitted to base station 10 across the cellular communications link. Accompanying this information may be a message which indicates how long since the receipt of the time trigger signal it has been. This "delta time" can be computed by remote sensor 20 using an onboard clock. Knowing the time difference between the original command to initiate a position fix and the time taken to collect and process the satellite data, server 200 can compute the location of remote sensor 20 in a customary fashion. The pseudorange information from remote sensor 20 may be processed along with DGPS correction information at server 200 in order to obtain the precise location of remote sensor 20. Note that the DGPS correction information must be that for the general area in which remote sensor 20 is located. DGPS corrections are available for various area from various services, for example Differential Corrections, Inc., which provides such information for various areas of the United States. Such DGPS corrections could be used at server 200 to refine the position calculation for remote sensor 20. The computed

location of remote sensor 20 may then be transmitted via Internet 5 back to computer 1 where it is displayed for the user.

In summary, a user accesses server 200 using a computer 1. As part of this access, the user may provide an identification code which serves to uniquely identify remote sensor 20. Server 200 then interrogates the remote sensor 20 which is identified based on the identification code. In response, the remote sensor 20 transmits positioning data to the server 200 where it is analyzed to derive the location of the remote sensor 20. T