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Description  |
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FIELD OF THE INVENTION
The present invention relates generally to real time positioning systems
and, more particularly, to the use of such systems to control access to
computer databases to assist in task scheduling.
BACKGROUND
Personal Digital Assistants (PDAs) have become more and more common in
today's society. The term PDA refers generally to mobile computer systems,
typically handheld, which users employ for a variety of tasks such as
storing telephone and address lists (databases), calendaring information,
task (i.e., to-do) lists, etc. Some PDAs also incorporate a wireless
communication link, allowing the unit to operate as a portable facsimile
device, Internet access device and/or pager. Further, PDAs can be
configured to operate with Global Positioning System (GPS) receivers as
described in U.S. Pat. No. 5,528,248 to Steiner et al., entitled "Personal
Digital Location Assistant Including a Memory Cartridge, A GPS Smart
Antenna and a Personal Computing Device" assigned to the assignee of the
present invention and incorporated by reference herein.
The GPS utilizes signals transmitted by a number of in-view satellites to
determine the location of a GPS antenna which is connected to a receiver.
Each GPS satellite transmits two coded L-band carrier signals which enable
some compensation for propagation delays through the ionosphere. Each GPS
receiver contains an almanac of data describing the satellite orbits and
uses ephemeris corrections transmitted by the satellites themselves.
Satellite to antenna distances may be deduced from time code or carrier
phase differences determined by comparing the received signals with
locally generated receiver signals. These distances are then used to
determine antenna position. Only those satellites which are sufficiently
above the horizon can contribute to a position measurement, the accuracy
of which depends on various factors including the geometrical arrangement
of the satellites at the time when the distances are determined.
Distances measured from an antenna to four or more satellites enable the
antenna position to be calculated with reference to the global ellipsoid
WGS-84. Local northing, easting and elevation coordinates can then be
determined by applying appropriate datum transformation and map
projection. By using carrier phase differences in any one of several known
techniques, the antenna coordinates can be determined to an accuracy on
the order of .+-.1 cm.
Although U.S. Pat. No. 5,528,248 describes how a GPS receiver can be
integrated with a PDA to display navigation information for a user, it
does not describe how positioning information provided to the PDA can be
used in other ways.
SUMMARY OF THE INVENTION
According to one embodiment, a computer assisted method of scheduling tasks
is provided. The method allows a task description to be stored in a
database accessible by a mobile computer system. The mobile computer
system receives positioning information corresponding to its geographic
location and indexes the database based on the positioning information
when the information indicates that the mobile computer system is in a
geographic location that facilitates completion of a task associated with
the task description.
The database may be resident in the mobile computer system or accessible in
other ways, for example, via the Internet. The task description preferably
includes a geocode which corresponds to the geographic location at which
completion of the task may be facilitated. The task description may also
include textual, voice or other messages which can be displayed and/or
played back to a user. The positioning information may be obtained from a
GPS satellite, a GLONASS satellite or a pseudolite. The mobile computer
system may be a portable unit, such as a PDA, or integrated within a
vehicle.
A second embodiment provides a computer assisted method of using a geocoded
database. In this embodiment, a mobile computer system is transported to a
first location having first geographic coordinates at a first time. At the
first location, RF signals which contain information indicative of the
location of a source of their transmission are received and processed to
derive the geographic coordinates of the first location. The geographic
coordinates of the first location are associated with a descriptor
indicative of the first location in a database associated with the mobile
computer system so as to form a geocoded entry in the database and a task
to be accomplished at the first location is similarly associated with the
geocoded entry in the database.
The mobile computer system is transported to a second location at a second
time and RF signals containing information indicative of the source of the
signals are received and processed to determine the geographic coordinates
of the second location. The geographic coordinates of the second location
are analyzed to determine whether the second location is within a
predetermined range of the first location and, if so, a user is alerted.
The user may be alerted by displaying an alert message, such as a task
description corresponding to the task to be accomplished at the first
location, on a display associated with the mobile computer system.
A further embodiment provides a mobile computer system having a location
determination unit configured to receive and process RF signals containing
information indicative of the location of a source of the signals, a
database coupled to the location determination unit and including location
coordinates indicative of a location of interest and a database interface
unit configured to access the database according to the location of the
mobile computer system.
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:
FIG. 1 illustrates a digital system configured with a mobile computer
system, a location determination unit and a database according to one
embodiment; and
FIG. 2 illustrates a vehicle configured in accordance with the present
invention located near a pick-up location.
DETAILED DESCRIPTION
The following description of a position based personal digital assistant
sets forth numerous specific details in order to provide a thorough
understanding of the present invention. However, after reviewing this
specification, it will be apparent to those skilled in the art that the
present invention may be practiced without some or all of these specific
details. In other instances, well known structures, programming techniques
and devices have not been described in detail in order not to
unnecessarily obscure the present invention.
Some portions of the detailed description which follows are presented in
terms of operations on data within a computer memory. These descriptions
are the means used by those skilled in the relevant arts to most
effectively convey the substance of their work to others skilled in the
art. The steps are those requiring physical manipulations of physical
quantities. Usually, though not necessarily, these quantities take the
form of electrical or magnetic signals capable of being stored,
transferred, combined, compared and otherwise manipulated. It has proven
convenient at times, principally for reasons of common usage, to refer to
these signals as bits, values, elements, symbols, characters, terms,
numbers or the like. It should be borne in mind, however, that all of
these and similar terms are to be associated with the appropriate physical
quantities and are merely convenient labels applied to these quantities.
Unless specifically stated otherwise, it will be appreciated that
throughout the description of the present invention, use of terms such as
"processing", "computing", "calculating", "determining", "displaying" or
the like, refer to the action and processes of a computer system, or
similar electronic computing device, that manipulates and transforms data
represented as physical (electronic) quantities within the computer
system's registers and memories into other data similarly represented as
physical quantities within the computer system memories or registers or
other such information storage, transmission or display devices.
Referring to the accompanying FIG. 1, a digital system 5 having a database
10, a mobile computer system 20 and a location determination unit 30 is
shown. Database 10 may be a separate database maintained at some location
remote from mobile computer system 20 or it may be a local database
maintained within mobile computer system 20. Mobile computer system 20 may
be a personal digital assistant or other mobile computer system (e.g., a
notebook or other personal computer) or it may be an integrated computer
system within a vehicle. Location determination unit 30 may be a Global
Positioning System (GPS) receiver of other unit capable of determining a
geographic location of an accompanying antenna 32.
It should be appreciated that although database 10, mobile computer system
20 and location determination unit 30 are illustrated as distinct units,
in some embodiments these items may comprise a single unit, such as a
personal digital assistant or notebook computer. In such embodiments,
location determination unit 30 may be housed within a card (PC Card)
compatible with the Personal Computer Memory Card International
Association PC Card Standard, release 2.0, published by the Personal
Computer Memory Card Interface Association (PCMCIA), September 1991. In
other embodiments, location determination unit 30 may comprise a GPS Smart
Antenna or other GPS receiver.
In yet other embodiments, elements of digital system 5 may form an
integrated system within a vehicle, aircraft, boat or other mobile unit
and database 10 may be stored within a memory device housed in a PC Card
or on another transportable computer readable media such as a disk or CD
ROM. Database 10 is preferably a geocoded database and will be described
in further detail below. In some cases, mobile computer system 20 may
share some circuitry with location determination unit 30. For example, the
two units may share a digital signal processor or other microprocessor
which performs the computations required to derive the geographic location
of the digital system 5 (i.e., antenna 32) using signals transmitted by
GPS satellites or other sources (e.g., GLONASS satellites and/or
pseudolites).
Mobile computer system 20 typically includes a microprocessor 21 and a
system bus 22. Microprocessor 21 is coupled to system bus 22, allowing
microprocessor 21 to communicate with the other elements which make up
mobile computer system 20, location determination unit 30 and database 10.
Mobile computer system 20 may also include a ROM 23 which typically stores
computer readable instructions to be executed by microprocessor 21 upon
power up. Such instructions may further include an operating system for
mobile computer system 20 where such an operating system is not stored
within another nonvolatile memory. Mobile computer system 20 may further
include a memory (Mem) 24 which may be a volatile memory (i.e., a random
access memory or RAM) for use during periods when mobile computer system
20 is powered up. The Mem 24 may also include a hard disk or other long
term, nonvolatile memory for storage of application programs and/or data
when mobile computer system 20 is not powered up. In other cases, these
application programs may be stored in ROM 23. ROM 23 and Mem 24 are
typically coupled to system bus 22 to allow access by microprocessor 21.
In some embodiments, ROM 23 and Mem 24 may be coupled to microprocessor 21
over a separate memory bus (not shown).
To facilitate use of mobile computer system 20 by an operator, user
interface 25 and display 26 are provided and each are coupled to system
bus 22. User interface 25 may include a familiar keyboard and mouse (or
other pointing device such as a pen). In addition, some mobile computer
systems 20 may have a voice synthesizer included as part of user interface
25 to allow activation of various functions by voice command. In other
embodiments, the user interface 25 may be a touch sensitive screen which
also forms part of a visual display 26. Other user interfaces may also be
used. Display 26 may be a visual display such as a liquid crystal display
screen, or other screen. In other embodiments, display 26 will include
alert lights, such as those commonly found on automobile dashboards. Where
mobile computer system 20 is integrated within a vehicle, display 26 may
form part of a heads up display or dashboard display within the vehicle.
When display 26 forms part of a heads up display, the heads up display may
provide information such as the vehicle's current speed and location
(e.g., latitude and longitude). The heads up display may further include
an area for displaying text messages, such as the task description stored
in database 10. Alternatively, the heads up display may only provide an
alert indication (such as an icon or an alert symbol, etc.). Such a heads
up display may be displayed on an appropriate section of the vehicle's
windshield, such as a corner of the windshield near the driver's position
or directly above the steering wheel, so as to allow for easy use by the
driver without obstructing the driver's view of the road. Display 26 may
also include a voice synthesizer (optionally shared with user interface
25) and speaker system to allow for playback of voice messages. This
arrangement may allow for voice messages to be played back through the
vehicle's existing sound system (e.g., an AM/FM stereo system). Other
displays may also be used.
Mobile computer system 20 also includes interface 27 which allows mobile
computer system 20 to communicate with location determination unit 30.
Interface 27 provides an electrical connection between mobile computer
system 20 and location determination unit 30 and may correspond to an
RS-232 or RS-422 interface. In some embodiments, where location
determination unit 30 comprises a GPS server located as a unit on a
vehicle bus system, interface 27 allows for proper electrical coupling
between mobile computer system 20 and a vehicle communication bus. As
such, interface 27 will be configured according to the protocol for
message exchange across the bus.
A communications bus is useful for delivering data and other electronic
signals from one device to another in a vehicle. Without use of such a
bus, as the number of vehicle devices increases, duplication of vehicle
sensors and increasing use of point-to-point wiring between devices is
required, which can result in large and needlessly complex wiring looms.
Use of such a bus allows use of unduplicated vehicle sensors and minimizes
use of point-to-point wiring, by making all measurements and signals
available simultaneously to all devices that are connected by the bus.
Several standards for such vehicle bus systems exist, for example, the
J1587 and J1708 specifications for bus systems published by the Society of
Automotive Engineers and the standards for communication buses as set
forth by the Society of Automotive Engineers and Controller Area Network
(CAN) as documented in ISO 11893:1993, for high speed applications, and in
ISO 11519.1:1994-ISO 11519.4:1994, for low speed applications, all of
which are incorporated herein by reference.
The J1587 (issued as 1988 January and in revised form as 1994 Jan. 10 and
later revisions) and J1708 (issued as 1986 January and in revised form as
1990 Oct. 5 and later revisions) specifications recite standards and
define signal formats for use of microcomputer systems in heavy duty
vehicle applications, such as provision of electronic data on vehicle and
component performance, vehicle routing and scheduling, vehicle driver
information and vehicle cargo reformation. Each signal that is transmitted
using a signal bus complying with these standards includes: (1) a message
identification (MID) number (three digits from 0-255, with MIDs 0-127
being defined in J1708 and MIDs 128-255 defined in J1587); (2) one or more
measured parameter values associated with and identified by the MID; and
(3) a check sum. Parameter update time intervals and priorities for
transaction of different groups of MIDs are currently being developed.
The user segment components of a GPS system carried on a vehicle are
connected using a communications bus in the same manner as are other
devices on the bus. An electrical connection between the server and the
bus is made using interface circuitry that complies with applicable
standards. Inexpensive interface ICs are readily available for buses that
conform to the CAN standards.
Typically, each device that is part of a GPS user segment on a vehicle will
have a unique bus address. GPS data can be provided or delivered in two
ways. First, a GPS user segment device (such as location determination
unit 30) can provide vehicle location, vehicle velocity and/or absolute or
local time information for use on the vehicle, using packets that identify
the source and destination(s) addresses of such data on the bus and that
identify the type of data (location, velocity, time, etc.) contained in
the packet.
Second, the GPS data can be provided at a central server, and any device
(such as mobile computer system 20) requiring such data can address a data
request to the GPS server. The server then packages the requested data in
a packet, frame or other suitable format and sends the packaged data
directly to the requesting device, using the bus. This approach may be
more flexible in that it (1) allows a client to request and promptly
receive GPS data and non-GPS data, (2) allows data to be requested and
received only when such data is needed, rather than transporting all data
on the bus as soon as such data is available, regardless of need, and (3)
provides such data in more convenient formats for individual client use.
Related GPS data may include GPS receiver health, GPS receiver correction
status, vehicle tracking status and other similar information. Information
can also be provided to, and stored on, the server to improve or correct
the GPS receiver performance. Such information may include real time clock
information, to reduce the time required for initial acquisition or
reacquisition of GPS satellite signals, and may include DGPS correction
data to improve the accuracy of real time determination of vehicle present
location. Such DGPS correction data may be obtained from a variety of
commercial or other sources using well-known radio-based communications
links such as FM subcarriers, private or packet radio links to private
servers or servers accessed through the Internet or other cellular phone
links.
Location determination unit 30 has an associated antenna 32 for receiving
signals from GPS satellites and/or other sources of GPS signals (e.g.,
pseudolites, FM subcarriers, etc.) Antenna 32 provides the received
signals to Receiver (Rx) Front-end 34 where the signals are downconverted
and often digitized for further processing by GPS Processor 36.
The manner in which GPS processing is accomplished is well known in the
art. Briefly, GPS receivers normally determine their position by computing
relative times of arrival of signals transmitted simultaneously from a
multiplicity of GPS satellites. These satellites transmit, as part of
their message, both satellite positioning data as well as data on
satellite clock timing and "ephemeris" data for each satellite. Using this
data, the GPS receiver computes pseudoranges which are simply the time
delays measured between the received signal from each satellite and a
local clock.
Many GPS receivers utilize correlation methods to compute pseudoranges. GPS
signals contain high rate repetitive signals called pseudorandom (PN)
sequences. The codes available for civilian applications are called C/A
codes, and have a binary phase-reversal rate, or "chipping" rate, of 1.023
MHz and a repetition period of 1023 chips for a code period of 1 msec. The
code sequences belong to a family known as Gold codes. Each GPS satellite
broadcasts a signal with a unique Gold code. For a signal received from a
given GPS satellite, following the downconversion process to baseband, a
correlation receiver multiplies the received signal by a stored replica of
the appropriate Gold code contained within its local memory, and then
integrates, or lowpass filters, the product in order to obtain an
indication of the presence of the signal. This process is termed a
"correlation" operation. By sequentially adjusting the relative timing of
this stored replica relative to the received signal, and observing the
correlation output, the receiver can determine the time delay between the
received signal and a local clock. The initial determination of the
presence of such an output is termed "acquisition." Once acquisition
occurs, the process enters the "tracking" phase in which the timing of the
local reference is adjusted in small amounts in order to maintain a high
correlation output. The correlation output during the tracking phase may
be viewed as the GPS signal with the pseudorandom code removed, or, in
common terminology, "despread." This signal is narrow band, with bandwidth
commensurate with a 50 bit per second binary phase shift keyed data signal
which is superimposed on the GPS waveform.
The above operations are performed by GPS processor 36 (or by a common
processor such as microprocessor 21 where location determination unit 30
and mobile computer system 20 share such circuitry) and may be achieved in
dedicated hardware or software. The output will be the geographic
coordinates (e.g., latitude, longitude and altitude) of the antenna 32. It
is assumed here that antenna 32 is positioned such that there is no
appreciable difference between its geographic coordinates and those of
mobile computer system 20. Also, the positioning information provided by
location determination unit 30 may be enhanced through the use of DGPS
techniques as is common in the art.
The output of GPS processor 36 is communicated to mobile computer system 20
via interface 38. Interface 38 may be an RS-232 or RS-422 interface.
Alternatively, where location determination unit 30 operates as a GPS
server, providing location information to a variety of systems within a
vehicle, interface 38 will be configured to provide appropriate electrical
coupling to a bus interconnecting the various vehicle systems.
As mentioned above, database 10 is preferably a geocoded database. This
term is best understood with reference to the manner in which digital
system 5 is used by an operator. Typically, mobile computer system 20 will
store various application programs, including a scheduling program which
allows an operator to store reminders in the form of "To-Do" lists or
other forms. Such scheduling programs are common in the art and often
allow the user to prioritize tasks to be accomplished according to a
variety of criteria, including due dates, etc. The present invention
provides a means by which tasks can be scheduled and/or prioritized based
on location. Tasks are assigned using a task descriptor (e.g., a text
and/or voice message describing the task) and stored in database 10.
Typically, the task descriptor will include a reference indicating a
location at which the task is to be accomplished. This may be a set of
geographic coordinates or, more typically, a name of a business or other
location. To illustrate, if the task descriptor is a text message such as
"PICK UP MILK", an appropriate reference might be "GROCERY STORE".
FIG. 2 illustrates an exemplary situation where a vehicle 100 includes a
digital system 5. Vehicle 100 has reached a location 102 which is located
a distance "R" from a GROCERY STORE 104. Assuming that a user has
previously stored a "PICK UP MILK" task with a reference to the GROCERY
STORE as described above, the user will be alerted to "PICK UP MILK" in
accordance with the present invention. The manner in which this is
accomplished is discussed further below.
After entering the task description in the database, the user will
transport mobile computer system 20 such that it is able to access the
database 10 (either because database 10 is contained within mobile
computer system 20, for example, within Mem 24 or as a PC card or other
computer readable storage medium, or because the units are linked via a
wireless communications link which may be routed through a cellular
telephone or modem system and/or the Internet) and is further able to
receive position information from location determination unit 30. Often,
mobile computer system 20 will be a PDA and database 10 will either be
stored within internal memory (e.g., Mem 24) or within a memory unit on a
PC Card or other device attached to the PDA. In such cases, the PDA may
also include location determination unit 30. In other cases, the PDA may
connect to a docking port or other coupling arrangement within a vehicle.
In these cases, location determination unit 30 may operate as a GPS server
within the vehicle as discussed above. Of course, mobile computer system
20 itself may be an integrated unit within the vehicle, in which case a
memory component such as a PC Card or CD ROM on which database 10 is
stored may be the only unit transported by the user. The memory component
would be provided to an appropriate device (for example a PC Card port or
CD ROM drive), thus making database 10 accessible by mobile computer
system 20. Further, database 10 may be maintained on the user's home or
business computer system and may be accessed by mobile computer system 20
via a wireless communication link. In some cases, the communication link
may be a cellular telephone link. Additionally, the communication link may
route messages between mobile computer system 20 and database 10 via the
Internet using techniques well known in the art. Although such a link has
not been shown in FIG. 1 in order not to obscure the drawing, it will be
appreciated that such a communication link would allow database 10 to be
updated by more that one user at various times.
At some point, location determination unit 30 will receive and process GPS
signals in the manner described above and will provide geographic location
coordinates to mobile computer system 20 via interface 38. These
geographic location coordinates will correspond to the geographic location
of antenna 32, however, it is assumed that mobile computer system 20 is in
close enough proximity to antenna 32 such that the location of antenna 32
is substantially the same as the location of mobile computer system 20.
This condition will be satisfied, for example, if mobile computer system
20 is transported within the same vehicle as that on which antenna 32 is
located. Antenna 32 may be a patch antenna or other antenna suitable for
mounting on a vehicle and capable of receiving GPS signals transmitted by
GPS satellites or pseudolites.
Once mobile computer system 20 has received the above-mentioned geographic
location coordinates (or other positionin | | |
