Abstract: Thermal drifts compensation method in a gaging device (1) with a transducer; the compensation method includes the steps of: determining and storing, in the course of a calibration operation, values of a thermal compensation coefficient (K) upon variation of a temperature (T) of the gaging device (1); detecting, in the course of a gaging operation, a current reading (X) of the gaging device (1); detecting, in the course of the gaging operation, a current temperature (T) of the gaging device (1); determining, in the course of the gaging operation, the current value of the thermal compensation coefficient (K) by means of the values of the thermal compensation coefficient (K) previously determined and stored in the course of the calibration operation as a function of both the current temperature (T) of the gaging device (1) and the current reading (X) of the gaging device (1); and correcting, in the course of the gaging operation, the current reading (X) of the gaging device (1) by means of the current value of t

Abstract: A new and useful method is provided for Goos-Hanchen compensation in an optical autofocus (AF) system that uses light reflected from a substrate to determine changes in the z position of a substrate. According to the method of the invention reflected light from the substrate is provided at a plurality of wavelengths and polarizations, detected and used to make corrections that compensate for the errors due to the Goos-Hanchen effect.

Abstract: A measuring apparatus (1; 1?) for measuring a manipulator (10), with a measuring body (2; 2?) having at least one measurement point (3; 3?) that is fixed in relation to the measuring body for determining a position (TTCP,3; TTCP,3?) relative to a reference point (TCP) that is fixed in relation to the manipulator, and an attaching device connected to the measuring body (5) for fixing on the surroundings, includes at least one calibration point (7; 7?) connected to the measuring apparatus for determining a position (TR, M; TR,M?) relative to the surroundings and/or at least one measurement point (6) positioned on the attaching device.

Abstract: A power steering apparatus includes a motor unit, and a driven device such as a pump or worm gearing. The motor unit includes an electric motor and an electrical control unit which are mounted in a common housing. The electric motor is provided with a rotation sensor. The electric motor and the rotation sensor are electrically connected to the electrical control unit within the housing. The rotation sensor is calibrated before the driven device is coupled to the motor unit.

Abstract: Provided is an apparatus for precisely correcting position and attitude information of a camera by analyzing image information received through a three line scanner in operation of the camera obtaining the position and attitude information from a Global Navigation Satellite System (GNSS) and an Inertial Navigation System (INS), and a method thereof. The method for correcting position and attitude information of a camera includes the steps of: a) calculating the position of the camera by using the GNSS; b) calculating the attitude of the camera by using the INS; c) generating the position and attitude correction information of the camera by analyzing an image received through a three line scanner mounted in the camera; and d) receiving a feedback of the position and attitude correction information in the GNSS and the INS.

Abstract: A method for determining dynamic errors in a measuring machine that gives the position of a mobile element of the machine in a working space with respect to a reference system, comprising: a calibration step, defined in which is at least one input-output model, which describes the dynamic behaviour of at least part of the measuring machine; said input-output model yields, in response to at least one input quantity u, a plurality of output quantities y, which comprise, among other things, the position error introduced in the measurement of position by the elastic deformations of parts of the machine that undergo dynamic deformation; a step of definition of an estimator filter that yields, in response to measured values of input quantities u and, in response to measured values of a subset of the output quantities y, an estimate of the position error; the filter is obtained by means of an analytical method based upon the input-output model; and a step of continuous real-time reconstruction of the error, in which

Abstract: An adaptive method and device for identification and compensation of errors in resolver output signals which can increase the accuracy of position estimates of the resolver angle is disclosed. The method utilizes the ideal orthogonal relationship of two resolver output devices to determine an error factor. The error factor is then used to correct the resolver position estimate.

Abstract: A positioning system (1) provided with an actuator (2) having a wave gear device (4) is driven and controlled by a semi-closed loop control for controlling the load position of a load device (5) based on the motor position of a motor shaft (31) of a motor (3). In a method for compensating for an angular transmission error by compensating for a motor shaft synchronous component ?Sync that occurs in synchrony with the motor position and is a relative rotation-synchronous component that includes an angular transmission error component of the wave gear device (4), the positioning system (1) is represented as a two-inertia model, and the motor shaft synchronous component ?Sync is represented as an oscillation source for producing a twisting action between the two inertia bodies in the two-inertia model.

Abstract: According to one embodiment of the present invention, a method for adjusting a position of an object to compensate for tilt includes providing a rotatable base supporting an object and directing the object relative to the base such that the position of the object is controlled relative to a first axis. The object is stabilized along a second axis. The object is positioned relative to the base using at least one bearing arm. The at least one bearing arm movably couples the object to the base at a first position relative to a third axis and a fourth axis. The at least one bearing arm includes a first portion and a second portion, which are coincident with the third axis and fourth axis, respectively. The object is adjusted to a second position using the at least one bearing arms to maintain the first axis when a tilt angle of the base is detected.

Abstract: Methods are disclosed wherein the structural health of a civil structure, such as, but not limited to, a bridge or the like is measured by electronic distance measurement from a plurality of stable locations to a plurality of cardinal points on the structure in a methodical manner. By measuring the coordinates of the cardinal points, the dynamic and long-term static behavior of the structure provide an indication of the health of the structure. Analysis includes; comparison to a Finite Element Model (FEM), comparison to historical data, linearity, hysteresis, symmetry, creep, damping coefficient, and harmonic terms.

Abstract: The linear position of a moving mechanical component is determined. A plurality of values of a quantity using a plurality of sensors is sensed and the sensed values are indicative of the linear position of the mechanical component. The plurality of sensed values are converted into a plurality of best linear position estimates concerning the mechanical component. One or more compensations are applied to at least some of the plurality of best linear position estimates. Each of the compensations are applied to account for a relative positioning of one of the plurality of sensors with respect to the others. A plurality of weighting factors associated with each of the plurality of best linear position estimates are determined. The position of the mechanical component is determined using the plurality of best linear position estimates and the plurality of weighting factors.

Abstract: The disclosure relates to a method for increasing the availability of displacement/position measuring systems on the basis of potentiometers with a slider tap in a closed control loop, the controller of which is formed by a microcontroller which is supplied with the position of the slider via an analog/digital converter. At least part of the sensor range of the potentiometer is scanned on request by presetting a sequence of manipulated variables and an available control loop variable which represents the position value at a high sampling rate outside process tasks is recorded, to determine the exact position of a defective slider position of the potentiometer by evaluating the variable. The reference variable of the control loop is overloaded in a defined manner within the process task such that the defective slider position is passed over during the displacement/position measurement and an intact slider position is reached.

Abstract: A controllable light source (102) is controlled to emit modulated light, preferably using a uniquely recognizable modulation pattern. A plurality of camera units (10) captures images that contain the light source. Clock time values at a time corresponding to capture of the image are captured from respective clock circuits (120) associated with the camera units (10) that capture the images. The modulated light is detected in the captured images. Relative calibration of the clock circuits (120) with respect to each other is performed using the associated clock time values of the images wherein the modulated light is detected.

Abstract: A method and systems for locating a source of particles, molecules, or fragments of molecules using particle, molecule, or fragment of molecule reception rate is disclosed. According to the invention, the particle, molecule, or fragment of molecules diffusion parameters in the search space are determined and a lattice is designed on the search space. After having determined whether or not at least one particle, molecule, or fragment of molecule is detected by a sensor, a probability is computed for each node of said search space lattice. The probability associated to each node of the search space lattice corresponds to the probability that the particle, molecule, or fragment of molecule source is located on the node. Then, the move of the sensor is evaluated according to the entropy of the computed probabilities.

Abstract: The present invention provides an apparatus and method for a robust and configurable mobile computer architecture with navigation computational capabilities. The present invention further provides a bus network which allows for an efficient and durable Input/Output (I/O) management system. The I/O management system has configurable connections to allow for modular addition, expansion, or replacement of navigation, crash detection, and communication line replacement units (LRUs). Additional I/O device connections allow several modes of input into the computational system. The present invention is a single, self-contained unit and provides an accessible user interface to the computer system.

Abstract: Disclosed are techniques and apparatus are provided for determining overlay error or pattern placement error (PPE) across the field of a scanner which is used to pattern a sample, such as a semiconductor wafer or device. This determination is performed in-line on the product wafer or device. That is, the targets on which overlay or PPE measurements are performed are provided on the product wafer or device itself. The targets are either distributed across the field by placing the targets within the active area or by distributing the targets along the streets (the strips or scribe areas) which are between the dies of a field. The resulting overlay or PPE that is obtained from targets distributed across the field may then be used in a number of ways to improve the fabrication process for producing the sample.

Abstract: A reference mirror 21 is disposed on a table 2, a first laser displacement sensor L1 for measuring a machined surface of a workpiece W and a second laser displacement sensor L2 for measuring a reference surface of the reference mirror 21 are disposed to a tool holder 3. A measurement motion applying section 24 causes the table 2 and the tool holder 3 to relatively move in a sinusoidal trajectory, and a sensitivity calculating section 28 calculates sensitivity of the first laser displacement sensor L1 based on machined-surface displacement data and reference-surface displacement data which are measured during the relative movement. Subsequently, an actual shape data calculating section 29 corrects the machined-surface displacement data based on the calculated sensitivity, and calculates actual shape data of the machined surface by taking the difference between the corrected machined-surface displacement data and the reference-surface displacement data.

Abstract: A method for reliable position monitoring includes: (a) transmitting two measured position values from a position measuring device to a first processing unit; (b) transmitting a setpoint value from a setpoint value generator to a second processing unit; (c) transmitting one of the two measured position values to the second processing unit; (d) transmitting the setpoint value to the first processing unit; (e) performing mutually independent comparisons between the setpoint value and the measured position values by the first processing unit and the second processing unit; and (f) monitoring the measured position values for an electronic shaft break between the position measuring device and the first processing unit. The position values are different and have a defined relationship with respect to each other, and the transmitting (a) includes alternately transmitting the two measured position values to the first processing unit.

Abstract: A position detecting device for a motor includes a resolver, amplifiers and a microcomputer. The microcomputer corrects an amplified sine wave signal to have the same amplitude in both positive and negative polarities, and corrects an amplified cosine wave signal to have the same amplitude in both positive and negative polarities. The microcomputer further corrects the corrected sine wave signal or the corrected cosine wave signal to have the same amplitude therebetween. The rotation position is determined accurately based on the sine wave signal and the cosine wave signal of the same amplitude, even if the amplifiers have different operation characteristics.

Abstract: An electric power generator system is provided with improved power efficiency due to a reduced sensitivity to errors in the sensing of angular rotor position. The system includes a power generator with a rotor, and a position encoder connected to sense angular position of the rotor and to generate a position signal accordingly. A processor receives the position signal, calculates an angular position in response, calculates an estimated angular position based on earlier received position signals, and finally generates a processed angular position based on the calculated angular position and the estimated angular position. This processed angular position is a more reliable measure of the rotor position, reducing the influence of short-term errors in the position signal, allowing normal wind turbine operation during temporary position encoder failure, and allowing an orderly shutdown during complete position encoder failure.

Abstract: The present invention relates a tilt and trim sensor apparatus having a housing and a shaft rotatably mounted to the housing. The apparatus includes a magnet connected to one of the housing and the shaft. The apparatus includes a transducer connected to another of the housing and shaft. The transducer is disposed adjacent to the magnet for sensing the position of the magnet and is operable to generate an output representative of an angular position of the magnet. The apparatus has a microprocessor for sensing gauge display input requirements. The apparatus has output circuitry for outputting a signal based on the output of the transducer that is in accordance with the gauge display input requirements.

Abstract: A distortion compensation method includes determining an undisturbed phase for at least one of a first position indication signal and a second position indication signal. The method includes determining an undisturbed ratio that relates the amplitude of the first position indication signal at a first frequency to the amplitude of the second position indication signal at a second frequency. The method also includes determining a disturbed amplitude of the position indication signal and adjusting a position indication based on the disturbed amplitude and phase, the undisturbed amplitude ratio, and the undisturbed phase. The method further comprises determining a relationship between the eddy current phase of the first position indication signal and the second position indication signal.

Abstract: In a device and method for computer-assisted 2D navigation in a medical procedure, parameters of projection matrices of a 3D calibration process of a C-arm unit are used for the 2D navigation.

Abstract: A position calculation method and apparatus are described. The position calculation apparatus may include an inertial measurement unit and be configured to be coupled with at least one sensor unit for detecting a physical event for use in position calculation. The presence of and type sensor unit may identified, and the position processing to be undertaken may depend on this identification.

Abstract: A position detecting method includes the steps of forming an image of a mark on a sensor, performing a first process that processes a raw signal obtained from the sensor with plural parameters, performing a second process that determines an edge of a signal processed by the first process for each parameter, determining a parameter from a result of the second process obtained for each parameter, and calculating a position of the mark based on a determined parameter.

Abstract: An apparatus and method for identifying the position of a magnetic shaft are provided. N field sensors are adjacently positioned at fixed locations relative to the shaft's periodic field, corresponding to 180/N relative phase shifts. A table provides N>2 predetermined signal models and a pre-identified position associated with each. An interpolator compares a representation of the N measured sensor signals to at least two predetermined models to generate a correction signal that provides another pre-identified position. The correction signal depends on N sensors for every position of the shaft. The correction signal is used to incrementally choose said another pre-identified position from the table as an approximate position of the shaft in an iterative process to find the minimum correction signal and identify the position.

Abstract: Well bore servicing equipment is provided. The well bore servicing equipment comprises a first manipulator to grip a well bore work string, to raise the work string, and to lower the work string. The well bore servicing equipment further comprises a controller to receive a work string trajectory input and to automatically control the first manipulator to raise and lower the work string substantially in conformance with the work string trajectory input.

Abstract: An electric field generated by another electric field communications apparatus reaches electric field sensor ES. Electric field sensor ES outputs an electric signal in response to the changes in the electric field. The electric field that reaches electric field sensor ES enters a return path of the electric field communications apparatus that is a source of the electric field. By locating electric field sensor ES between receiver main electrode ERB and receiver return electrode ERG, electric field intensity at the location where electric field sensor ES is positioned. Therefore, sensitivity of the changes in electric field for electric field communications apparatus TRX can be improved.

Abstract: A first method determines a position of a point of interest on a target object surface in a target object coordinate system using orientation and distance measurements of a pointing instrument in an instrument coordinate system. A second method determines an orientation of a pointing instrument in an instrument coordinate system for the instrument to be aligned with a point of interest on a target object surface having a target object coordinate system, wherein a position of the point of interest in the target object coordinate system is known. A third method controls orientation of a laser beam of a laser in an instrument coordinate system for the laser beam to trace an image on a target object surface having a target object coordinate system, wherein positions of points for the image on the surface of the target object in the target object coordinate system are known.

Abstract: A method is disclosed whereby a laser-based spherical coordinate measurement system is dynamically calibrated. A mechanical oscillator, such as, but not limited to, a Foucault pendulum is used to generate periodic motions which can be fitted to Fourier series models. The residuals between the experimental measurements and the model can provide information which can be used to calibrate the instrument. The calibration information is used to augment the ASME B89.4.19-2006 standard to improve sensitivity to cyclic errors and include the servo systems.

Abstract: The disclosure relates to a method for commissioning pneumatically operated actuators that are controlled by a positioner. To determine the drive type, a constant flow of pneumatic fluid is applied to the actuator during commissioning while a drive-specific characteristic curve of the fed back position is recorded over time. Then the measured characteristic curve is compared with a given specimen characteristic curve. The drive type is inferred from the level of difference or agreement between the drive-specific characteristic curve and the specimen characteristic curve.

Abstract: A method according to the invention for adjusting or calibrating a vehicle surroundings sensor (15) comprises the steps of: attaching at least one target pair (20, 22) to the rear wheels (12, 14) of the motor vehicle (7); recording the target pair (20, 22) using at least one measuring unit (32, 46) and determining the vehicle axle (64) from the recording; placing at least one target (16, 18) in a known position relative to a vehicle surroundings sensor adjustment or calibration element (62); recording the target (18) placed at the vehicle surroundings sensor adjustment or calibration element (62) using the at least one measuring unit (32, 46) and determining the angular position of the vehicle surroundings sensor adjustment or calibration element (62) relative to the vehicle axle (64); aligning the vehicle surroundings sensor adjustment or calibration element (62) relative to the vehicle axis (64); and adjusting or calibrating the vehicle surroundings sensor (15) relative to the vehicle axis (64).

Abstract: A disclosed image forming apparatus for detecting position displacement patterns and correcting position displacement of an image forming position in a main scanning direction according to the detection result, includes a position displacement amount calculating part configured to calculate the amount of the position displacement according to the detection result, a position displacement correcting part configured to correct the position displacement by performing at least one of multiplication correction or multiplication error deviation correction, a correction amount calculating part configured to calculate a multiplication error deviation correction amount for correcting multiplication error deviation generated by the multiplication correction, a first determining part configured to determine whether to plot a first position displacement correction pattern included in the position displacement patterns for performing the multiplication error deviation correction according to the multiplication error devia

Abstract: The vibration characteristic of a dynamic AFM probe is simulated. For a given operation parameter (for example, the displacement u0 of the probe, the spring constant k of the cantilever, or the radius of curvature of the probe R1), the plate-spring cantilever to which the probe is attached is vertically moved while being mechanically resonated, and the vibration characteristic of the probe of the dynamic mode atomic force microscope (AFM) for observing the structure of the sample surface is simulated. The vibration information on the probe in the steady state at each initial position u0 (displacement u?time ?) (S103, S104) is recorded, and the movement of the probe is visualized by GUI on the basis of the recorded vibration information.

Abstract: Dynamic offset determination for each of a plurality of measurement systems for matching the systems is disclosed. One embodiment uses an artifact which is periodically run across the measurement system to be matched. Inputs for each run include the current offsets and historical data for the entire fleet and the new test measurement for the current measurement system under test. Evaluation based on exponentially weighted moving average and median calculation techniques may result in a new, reset offset for one or more measurement systems. The reset offset(s) is then applied to product measurements to nullify any tool matching issues.

Abstract: In a power-loss reducing system, a transmitting unit causes a radar to transmit a measurement radio wave, and a power monitoring unit monitors power of the measurement radio wave transmitted from the radar through a cover while changing a positional relationship between the cover and the radar. An extracting unit extracts a value of the changed positional relationship between the cover and the radar based on a result of the monitoring of the power such that the extracted value of the positional relationship allows reduction of power loss of a radar wave transmitted, through the cover, from the radar located based on the extracted value of the positional relationship.

Abstract: An inspection artifact includes a central portion and multiple optical and coordinate measurement machine (CMM) alignment features arranged on the central portion. The optical and CMM alignment features are configured to align the coordinates for an optical or a CMM measurement system to a common coordinate system. Another inspection artifact includes a central portion and multiple computed tomography (CT) alignment features arranged on the central portion. The CT alignment features are configured to align the coordinates for a CT system to a common coordinate system.

Abstract: Provided is method of calibrating Y-axis direction position of contact tip of form measuring instrument including: table rotatable about Z-axis; contact tip capable of contacting workpiece; and contact tip driving means to drive contact tip in at least X- and Z-axis directions among X-, Y- and Z-axis directions perpendicular to one another. Method performs tracing measurement of inclined surface or inclined cylinder side surface which is part of workpiece obtained by inclining workpiece placed on table about Y-axis, or side surface of off-centered cylinder having center axis off-centered in X-axis direction by rotating surface to obtain measurement value at each angular position of rotation of table, obtains angular position of rotation at which smallest value among measurement values of tracing measurement is detected as angular position of rotation with smallest detected value, and adjusts Y-axis direction position of contact tip based on angular position of rotation with smallest detected value.

Abstract: A method and system are provided for reducing a positioning error for positioning a light beam either onto or from a workpiece. A calibration mark is provided, and an image of the calibration mark is captured, to compare with a guide mark. The position of the guide mark corresponds to a set of design data or coordinates. The position of the image of the calibration mark is adjusted until the image matches with the guide mark. A set of vision compensating factors can therefore be determined. Thereafter, an image of a laser mark is captured, and adjusted to match the guide mark, to determine a set of scan head compensating factors. The design data can then be modified based on the vision compensating factors and the laser compensating factors, and used to position the laser beam onto the workpiece or capture light from a work piece to form an image.

Abstract: In a travel angle detection system for a mobile object having a detector installed in the mobile object to produce angular velocity outputs successively, the detector outputs are read and one output is determined as a provisional calibration value indicative of zero-point. Integrated values of differences between the calibration value and successive outputs and output variation width are calculated. When they are within predetermined permissible ranges, the mobile object is determined to be in static condition and the calibration value is corrected by an average value of the integrated values. The travel angle of the mobile object is detected from the calibrated outputs of the detector, thereby achieving accurate calibration of detector output by enabling accurate determination of the static condition.

Abstract: Measurements are acquired from a magnetic sensor during a non-pre-ordered movement, and a plurality of sets of solutions are determined for respective expected values of intensity of the Earth's magnetic field. The solutions are defined by a plurality of parameters, including at least one gain value for each detection axis of the magnetic sensor. For each solution, a figure of merit is determined, correlated to a calibration error, and a partial solution is selected in each set of solutions, based on the figure of merit. Once a gain confidence interval has been defined, a calibration solution is selected based on the figure of merit, from among the partial solutions having respective gain values all falling within the gain confidence interval.

Abstract: A method for determining a mixup in the terminals of a position encoder having a position encoder motor, which is bidirectionally drivable via a plurality of terminals, so that a mixup of at least two of the terminals of the position encoder motor leads to a reversal in the actuation direction of the position encoder, having the following steps of setting an actuating element of the position encoder to a zero setting, from which a motion of the actuating element is possible in one or two directions; driving the position encoder motor according to a diagnostic variable, which is selected so that, based on the actuation using the diagnostic variable, in the case of a non-mixup of the terminals and in the case of a mixup of the terminals, different absolute values of the changes are to be expected in the changes of the actuation position of the actuating element; recording a current change in the actuation position of the actuating element that comes about by the driving of the position encoder motor; establishi

Abstract: A positioning method includes: executing a first positioning mode or a second positioning mode, a first positioning process that is performed using a least-square method based on a positioning signal and a second positioning process that is performed using a Kalman filter based on the positioning signal utilizing a positioning result obtained by the first positioning process as a base value being performed in the first positioning mode, and the second positioning process being further performed in the second positioning mode utilizing a positioning result obtained by the second positioning process as a base value; determining accuracy of a positioning result obtained by the second positioning process performed in the executed positioning mode; and changing the positioning mode to be executed to the first positioning mode or the second positioning mode corresponding to the accuracy.

Abstract: A vehicle wheel alignment measuring method and apparatus capable of measuring wheel alignment of a vehicle body with high accuracy without wheels mounted in an assembly line. A dummy wheel (10) is mounted on a wheel mounting portion (6) on which a wheel is not mounted. Subsequently, with a vehicle body supported, a wheel mounting portion elevating means (8) elevates the wheel mounting portion (6) via the dummy wheel (10). Thereafter, an alignment measuring means (9) measures wheel alignment for the wheel mounting portion (6) on which the dummy wheel (10) is mounted.

Abstract: A method for calibrating alignment of an end effector with respect to a chuck in a plasma processing system is provided. The method including positioning the end effector over the chuck and taking a still image of the chuck and the end effector. The method including processing the still image to ascertain the center of the chuck and the end effector-defined center defined by the end effector. The method including determining a positional difference between the end effector-defined center and the center of the chuck.

Abstract: In an interferometer system and a method for its operation, the interferometer system includes an interferometer having an interferometer light source whose emitted radiation is able to be split into a measuring arm and a reference arm, an object to be measured being disposed in the measuring arm, and the interferometer delivering interferometer signals as a function of the position of the object to be measured. In addition, a detecting device is provided for detecting fluctuations in the refractive index of the air in the measuring arm and/or reference arm. The detecting device includes a spectrometer unit; the spectrometer unit has at least one spectrometer light source, as well as at least one spectrometer detector unit.

Abstract: A process and a device are provided for determining the pose as the entirety of the position and the orientation of an image reception device. The process is characterized in that the pose of the image reception device is determined with the use of at least one measuring device that is part of a robot. The device is characterized by a robot with an integrated measuring device that is part of the robot for determining the pose of the image reception device.

Abstract: The present invention provides a measurement apparatus which includes a scale and a sensor one of which is attached on a target object, and measures a position of the target object by reading the scale by the sensor, the apparatus including a detection unit configured to detect a shift amount of the scale from a reference position, and a calculation unit configured to correct, the position of the target object measured by reading the scale by the sensor, based on the shift amount of the scale from the reference position, which is detected by the detection unit.

Abstract: A two-axis gyroscope used on a bottom hole assembly can be used for determining a rate of rotation about the rotational axis of a BHA. The method takes advantage of possible misalignment of at least one axis of the two axis gyroscope from orthogonality with respect to the rotational axis of the BHA, resulting in the misaligned gyro being sensitive to BHA rotation.

Abstract: A location measurement system comprises: a GPS receiver for attachment to a person and for determining earth location of the person; a display for attachment to the person; memory for storing map data; a processor configured to process earth location and the map data to instruct display the person's current location with a map on the display.