Abstract: Various embodiments relate generally to autonomous vehicles and associated mechanical, electrical and electronic hardware, computer software and systems, and wired and wireless network communications to provide an autonomous vehicle fleet as a service. In particular, a method may include monitoring a fleet of vehicles, at least one of which is configured to autonomously transit from a first geographic region to a second geographic region, detecting data indicating an event associated with the vehicle having a calculated confidence level, receiving data representing a subset of candidate trajectories responsive to detecting the event, which is associated with a planned path for the vehicle, identifying guidance data to select from one or more of the candidate trajectories as a guided trajectory, receiving data representing a selection of a candidate trajectory, and transmitting the selection of the candidate trajectory as of the guided trajectory to the vehicle.

Abstract: A system and method that function to generate an updated vehicle state based on a previous vehicle state and a set of sensor measurements. The previous vehicle state can be selected from a set of redundant prior vehicle state candidates. The system and method can optionally detect and correct for sensor measurement faults or failures, prior to updating the vehicle state.

Abstract: Methods and systems for a clean fuel, manned or unmanned aircraft, having an electric, low-emission or zero-emission lift and propulsion system, an integrated ‘highway in the sky’ avionics system for navigation and guidance, a tablet-based motion command, or mission planning system to provide the operator with drive-by-wire style direction control, and automatic on-board-capability to provide traffic awareness, weather display and collision avoidance. Automatic computer monitoring by a programmed multiple-redundant autopilot control units control each motor-controller and motor to produce pitch, bank, yaw and elevation, while simultaneously restricting the flight regime that the pilot can command, to protect the pilot from inadvertent potentially harmful acts that might lead to loss of control or loss of vehicle stability. By using the results of the state measurements to inform motor control commands, the methods and systems contribute to the operational simplicity, reliability and safety of the vehicle.

Abstract: Disclosed is a calibration method for a rotating accelerometer gravity gradiometer, wherein linear motion error coefficients, angular motion error coefficients, self-gradient model parameters and scale factors of the rotating accelerometer gravity gradiometer are calibrated once by changing linear motion, angular motion, and self-gradient excitations of the rotating accelerometer gravity gradiometer. The calibrated linear and angular motion error coefficients are used for compensating for motion errors of the gravity gradiometer online, and the calibrated self-gradient model parameters are used for self-gradient compensation. The calibration method provided by the present invention is easy to operate and not limited by any calibration site, thereby being suitable for programmed self-calibration and realizing an important engineering value.

Abstract: This disclosure relates to an underground mining vehicle comprising a three-axis MEMS gyroscope rotatable about a rotation axis and a gyroscope interface that calculates a first rotation rate bias with respect to a first axis different to the rotation axis, a second rotation rate bias with respect to a second axis different to the first axis and different to the rotation axis, a rotation rate about the rotation axis based on the Earth rotation rate vector by correcting the rotational measurement data using the first rotation rate bias and the second rotation rate bias and a third rotation rate bias with respect to the rotation axis based on the calculated rotation rate about the rotation axis. A navigation unit receives the first rotation rate bias, the second rotation rate bias and the third rotation rate bias and calculates a pose of the vehicle.

Abstract: A system combines contributions from various sensors to obtain an object's position, velocity, or orientation.

Abstract: A system and method that function to generate an updated vehicle state based on a previous vehicle state and a set of sensor measurements. The previous vehicle state can be selected from a set of redundant prior vehicle state candidates. The system and method can optionally detect and correct for sensor measurement faults or failures, prior to updating the vehicle state.

Abstract: A system combines contributions from various sensors to obtain an object's position, velocity, or orientation.

Abstract: An inertial measurement unit includes a substrate having MEMS gyroscopes arranged on the substrate as opposing pairs. The gyroscopes of each opposing pair are arranged on opposite sides of an axis of rotation of the substrate and each opposing pair has a central axis that intersects an axis of rotation of the substrate. A processor receives a rotational measurement from each gyroscope, compares the measurements from gyroscopes of each opposing pair, determines a mean or median rotation value for each opposing pair, and compares the mean or median rotation value with a threshold value. The processor assigns a weight to the mean or median value for each opposing pair and determines a rotation of the cuboid inertial measurement unit based on the mean or median value for each opposing pair and the respective weight for the mean or median value for each opposing pair.

Abstract: A system combines contributions from various sensors to obtain an object's position, velocity, or orientation.

Abstract: A device for exerting torque on an object includes: at least one rotating mass rotatably supported about an axis of rotation; a drive for driving the rotating mass; a bearing which enables a change in the alignment of the axis of rotation relative to the object; and a coupling unit which engages on the bearing and couples the rotating mass to the object.

Abstract: Various embodiments relate generally to autonomous vehicles and associated mechanical, electrical and electronic hardware, computer software and systems, and wired and wireless network communications to provide an autonomous vehicle fleet as a service. In particular, a method may include receiving data associated with a sensor measurement of a perceived object, determining a label associated with the perceived object based on an initial calibration, retrieving log file data associated with the label, determining a calibration parameter associated with the sensor measurement based on the retrieved log file data, and storing the calibration parameter in association with a sensor associated with the sensor measurement. Sensors may be calibrated on the fly while the autonomous vehicle is in operation using one or more other sensors and/or fused data from multiple types of sensors.

Abstract: A device for measuring an inclination of a green in a golf course. The device includes: a rotation member (200) having a weight member (210) provided eccentrically relative to a central axis of the rotation member such that the rotation member (200) freely rotates around a rotation shaft (220), the rotation member (200) having horizontal and vertical measurement lines; a first casing (110) having an accommodation space (112); and a second casing (120) fitted over the first casing (110), the second casing (120) having first rotation graduations, a horizontal judge line (h) and a vertical judge line (v), wherein the rotation member (200) comes into close contact with both the first casing (110) and the second casing (120), and then is stopped by a pressure generated between the first and second casings or by simultaneously pressing both a flange (224) of the rotation shaft and the first casing (110).

Abstract: An integrated Reaction Wheel Assembly Array (RWAA) includes a multi-rotor chassis having a plurality of bearing locating features. A plurality of rotor assemblies is mounted to the multi-rotor chassis. Each rotor assembly includes a rotor having a rotor shaft, a spin motor coupled to the rotor and configured to drive rotation of the rotor about a spin axis, and a first spin bearing assembly disposed around an end portion of the rotor shaft. The first spin bearing pilots to one of the bearing locating features to position or locate the spin axis of the rotor assembly in a predetermined fixed spatial relationship relative to the spin axes of the other rotor assemblies.

Abstract: An antenna apparatus is provided which has a centroid close to a vibration isolation structure and which is hard to vibrate like a pendulum motion when vibration is applied. The antenna apparatus includes a first base plate, an antenna unit disposed at a side of the first base plate and supported by the first base plate, and a counter weight unit disposed at another side of the first base plate opposite to the antenna unit and supported by the first base plate. The antenna apparatus further includes a vibration isolation structure having one end fixed to the first base plate to suppress a vibration of the first base plate, and a second base plate to which other end of the vibration isolation structure is fixed and which is fixed to a moving object or a structural object.

Abstract: A sensor apparatus comprising a housing, two or three gyroscope units and three accelerometer units. The gyroscope units are oriented orthogonally respective to each other and mounted within the housing. Each gyroscope unit includes a plurality of gyroscopes with input axes parallel to each other. The accelerometer units are oriented orthogonally respective to each other and mounted within the housing. Each accelerometer unit includes a plurality of accelerometers with detection axes parallel to each other.

Abstract: Calibration systems and methods simultaneously calibrate a magnetic compass and gyroscopes. An exemplary embodiment rotates the field calibration system. Based upon the rotation sensed by the magnetic compass and the gyroscopes, the field calibration system determines compensation for both the magnetic compass and the gyroscopes.

Abstract: An azimuth determination system has a platform. A plurality of gimbals is attached to the platform to allow the platform to rotate about multiple axes. A pair of gryos is attached to the platform. A leveling device is attached to the platform to indicate when the platform is at a desired position. A control device attached to the plurality of gimbals to move the platform to the desired position indicated by the leveling device. An electronics system is to provide power to the azimuth determination system and to determine azimuth by positioning the gyros in a first position with an input axis of the gyros in the horizontal plane and orthogonal to the Earth Rate vector to calculate a first output and rotating the gyros 180° about the vertical to a second position to calculate a second output, the platform is then inverted and an additional set of two readings is taken. The four outputs are combined to produce the azimuth value and a gyro induced bias error.

Abstract: An apparatus for azimuth measurements is provided. The apparatus comprises a housing and a plurality of gyro sensors aligned in the housing. Each of the plurality of gyro sensors has an input axis for angular velocity measurements. There is provided a drive unit for rotating each of the plurality of gyro sensors about a rotation axis. Each of the plurality of gyro sensors changes orientation of the input axis with the drive unit.

Abstract: A jig for selecting a valve part number or a joint part number representing respective selected conditions required for selecting a valve or a joint comprising: a substantially rectangular base plate defining an inner space, and several sliding gauges laterally arranged in the inner space to slide in a longitudinal direction of the base plate, each of the sliding gauges comprising a condition description area including several conditions thereon from which the selected condition is determined, and a symbol description area including several symbols thereon, both the conditions and the symbols arranged in the sliding direction, several condition selecting windows laterally arranged, each of the condition selecting window being configured to expose one of the selected conditions, several symbol selecting windows laterally arranged, each of the symbol selecting window being configured to expose one of the selected symbols.

Abstract: A stride monitoring device that can be used particularly for sports applications and that includes a pair of shoes, one of which includes at least one magnetic mass, and the other includes at least a measurement device to make at least one measurement, and a processor for processing of the measurement. The measurement device includes at least one accelerometer and at least one magnetometer capable of outputting signals that can be processed to determine stride parameters.

Abstract: An apparatus for azimuth measurements is provided. The apparatus comprises a housing and a plurality of gyro sensors aligned in the housing. Each of the plurality of gyro sensors has an input axis for angular velocity measurements. There is provided a drive unit for rotating each of the plurality of gyro sensors about a rotation axis. Each of the plurality of gyro sensors changes orientation of the input axis with the drive unit.

Abstract: An apparatus for azimuth measurements comprises an elongated housing, a plurality of gyro sensors, each of the gyro sensors having an input axis for angular velocity measurements, spherical sensor holders arranged along the longitudinal direction of the housing, at least one motor for driving the sensor holders, a transmission mechanism for transmitting a rotation force from the motor to each of the sensor holders and a controller for controlling a rotation of the motor. Each of the sensor holders has one of the gyro sensors and is rotatable about a rotation axis so as to change the orientation of the input axis of the gyro sensor.

Abstract: The invention relates to a device for adjusting the angle of a sighting unit towards a target, in particular for a geodesic-measuring instrument. The inventive device comprises a reference base, at least one bearing for mounting the sighting unit thereon in such a way that it is pivotable with respect to said reference base around an axis, a gear for accurately adjusting an angle of rotation around said axis between the sighting unit and the reference base and a coupling unit for limiting or interrupting a torque flux around the axis. The gear and the coupling unit are in series arranged in the torque flux between the sighting unit and the reference base. The torque flux is carried out around the axis between the sighting unit and the reference base by means of the gear and the coupling unit when it is non-interrupted thereby.

Abstract: A system and method for using a survey tool within a borehole is provided. The survey tool includes a plurality of rotation sensors each having a sensing axis and a direction of least acceleration sensitivity. The sensing axes of the plurality of rotation sensors are generally parallel to one another and the directions of least acceleration sensitivity of the plurality of rotation sensors are generally non-parallel to one another.

Abstract: Apparatus, systems, and methods to control a plurality of gyroscopes utilizing intermediate frequencies are disclosed. The gyroscopes are configured to operate at the same pre-determined intermediate frequency. To accomplish this, the natural frequency of each gyroscope is determined, and a reference signal is added to the output signal of its respective gyroscope such that the sum of the natural frequency and the reference signal frequency equals the pre-determined intermediate frequency. The output signal from each gyroscope is transmitted to a common inertial data processor, and the inertial data processor outputs a directional signal. The directional signal includes a representation of angles from an X-axis, a Y-axis, and a Z-axis. Since each signal output by the gyroscopes has the same frequency, the loss of data is decreased and the accuracy of the data increased.

Abstract: A system and method for determining an orientation of the survey tool within a borehole utilizes a survey tool including a plurality of rotation sensors each having a sensing axis and a direction of least acceleration sensitivity. The plurality of rotation sensors are mounted in a housing with their sensing axes generally parallel to one another and with their directions of least acceleration sensitivity generally non-parallel to one another. The survey tool further includes a controller adapted to calculate a weighted average of the detected angular rotation rates from the plurality of rotation sensors. The weighted average includes the detected angular rotation rate of each rotation sensor about its sensing axis weighted by the detected acceleration along its direction of least acceleration sensitivity.

Abstract: A system and method for determining an orientation of the survey tool within a borehole utilizes a survey tool including a plurality of rotation sensors each having a sensing axis and a direction of least acceleration sensitivity. The plurality of rotation sensors are mounted in a housing with their sensing axes generally parallel to one another and with their directions of least acceleration sensitivity generally non-parallel to one another. The survey tool further includes a controller adapted to calculate a weighted average of the detected angular rotation rates from the plurality of rotation sensors. The weighted average includes the detected angular rotation rate of each rotation sensor about its sensing axis weighted by the detected acceleration along its direction of least acceleration sensitivity.

Abstract: An omnidirectional borehole navigation system is provided that includes a housing that can be placed within the smaller diameter drill pipes used towards the bottom of a borehole, an outer gimbal connected to the housing, and at least two or more stacked inner gimbals that are nested in and connected to the outer gimbal, the inner gimbals each having an axis parallel to one another and perpendicular to the outer gimbal. The inner gimbals contain electronic circuits, gyros whose input axes span three dimensional space, and accelerometers whose input axes span three dimensional space. There are an outer gimbal drive system, an inner gimbal drive system for maintaining the gyro input axes and the accelerometer input axes as substantially orthogonal triads, and a processor responsive to the gyro circuits and the accelerometer circuits to determine the attitude and the position of the housing in the borehole.

Abstract: A system is disclosed for using camera attitude sensors with a camera. A camera assembly includes a tripod base, a tripod head interface mounted on the tripod base, a tripod head mounted on the tripod head interface and a camera mounted on the tripod head. The tripod head enables the camera to pan and tilt. The system also includes a first optical encoder for detecting the amount that the camera has been panned and a second optical encoder for detecting the amount that the camera has been tilted. Two inclinometers are mounted on the tripod head interface to measure attitude of the tripod head. Two gyroscopes (“gyros”) are mounted on the camera assembly. Data from the encoders, gyros and inclinometers are packaged and sent to graphics production equipment to be used for enhancing video captured by the camera.

Abstract: An omnidirectional borehole navigation system is provided which features a housing for traversing a borehole; a gimbal system including at least one outer gimbal connected to the housing and at least one inner gimbal nested in and connected to the outer gimbal; a solid state three-axis gyro assembly mounted on the inner gimbal; a solid state three-axis accelerometer assembly mounted on the inner gimbal; gyro logic circuits on the inner gimbal responsive to the three-axis gyro assembly to produce the inertial angular rate about each gyro input axis; accelerometer logic circuits on the inner gimbal to produce the non-gravitational acceleration along each accelerometer input axis; and a microprocessor responsive to the gyro logic circuits and the accelerometer logic circuits for determining the attitude and the position and velocity of the housing in its borehole.

Abstract: A calculation system for calculating the control signals which are designed to perform a frequency-dependent weighting of the angular velocity signals and the angular position signals. The angular velocity indicators are preferably used for stabilization in a high frequency band while the angular position indicators are suitable for stabilization in a low frequency band. A further calculation system which is designed to perform the frequency-dependent weighting such that the control signals for frequencies below a certain frequency are substantially determined by the angular position signals and the control signals for higher frequencies are substantially determined by the angular velocity signals.

Abstract: Using an inertial master box mounted on a carrier for measuring its movements with respect to a geographic frame of reference of fixed directions along three axes Xg, Yg, Zg, a measuring method provides for continuously measuring an orientation of a frame of reference Xm, Ym, Zm tied to the inertial master box. Positioning is provided by applying a sequence of cycles of eight inversions of the inertial master box while keeping the axis Ym in a direction parallel to the axis Yg. A first motor causes a gimbal to pivot on a first axle secured to the carrier, while a second motor causes the inertial master box to pivot about a second perpendicular axle secured to the gimbal. A processor calculates three attitude angles by running a first inertial navigation program of the strapdown type and controls the first and second motors by running a second program.

Abstract: A two axis (azimuth and elevation) stabilized common gimbal (SGC) for use on a wide variety of commercial vehicles and military vehicles which are employed in combat situations capable of stabilizing a payload of primary sensors and of mounting a secondary sensor payload that is independent of the moving axes. The SCG employs three gyroscopes, inertial angular rate feedback for providing gimbal control of two axes during slewing and stabilization. In addition the third (roll) gyroscope is used for performing automatic calibration and decoupling procedures. In this regard, the SCG provides an interface for the primary suite of sensors comprising one or more sensors having a common line-of-sight (LOS) and which are stabilized by electronics, actuators, and inertial sensors against vehicle motion in both azimuth and elevation.

Abstract: The attitude of a tiltable body is tracked and controlled on the basis of signals outputted from gyros and tilt sensors. The signals outputted from the gyros are transformed and integrated to produce estimated position information in the form of a modified quaternion in which the yaw component is constrained to a zero value. Modified quaternion information in the same form is also generated from signals outputted from the tilt sensor and is used to detect and correct an error component in the estimated position information. Gyro drift is also corrected based on the output of the tilt sensor.

Abstract: An orientation measuring device with a plurality of precision tooled grooves, indentations or the like. Two precision tooled adaptor bodies, preferably of cylindrical shape, are removably mountable in the indentations, where appropriate, for a given measuring task. The adaptor bodies are held in place by, e.g., magnets. The device is capable of determining the spatial orientation of rolls, bars, hollow or solid cylinders, ranging from small to large diameters by appropriately selecting in which of the grooves or indentations the adaptor bodies are mounted.

Abstract: A calculation system for calculating the control signals which are designed to perform a frequency-dependent weighting of the angular velocity signals and the angular position signals. The angular velocity indicators are preferably used for stabilization in a high frequency band while the angular position indicators are suitable for stabilization in a low frequency band. A further calculation system which is designed to perform the frequency-dependent weighting such that the control signals for frequencies below a certain frequency are substantially determined by the angular position signals and the control signals for higher frequencies are substantially determined by the angular velocity signals.

Abstract: A sensor includes a plurality of weight portions which swivel, support parts each of which supports at one end a corresponding one of the plurality of weight portions in the same direction, and a driving part which supplies driving power to the support parts to swivel the plurality of weight portions. The driving part swivels at least one weight portion of the plurality of weight portions in a first direction and a remaining weight portion in a second direction opposite to the first direction so that the angular velocity about an axis parallel to a predetermined swivel locus of the at least one weight portion, excluding an acceleration component in the direction of the axis, can be detected from the difference between a deviation of a swivel locus of the at least one weight portion from the predetermined swivel locus and a deviation of a swivel locus of the remaining weight portion from a predetermined swivel locus thereof.

Abstract: A missile guidance system employs a strap down inertial measurement unit with a separate accelerometer and star sensor that are moved for preflight accelerometer initialization. During flight, light is directed on the accelerometer and inertial measurement unit to produce on the star sensor images of the light source, the accelerometer and the inertial measurement unit. The location of these images, which manifest the acceleration and position of the inertial measurement unit relative to the vehicle, are used to improve the accuracy of the inertial measurement unit data for vehicle guidance.

Abstract: This invention is a clear plastic board used specifically for scoring a straight line when place on top of glass or stained glass. The invention allows the artisan to comfortably move the board so as to score by seeing his pattern through the clear plastic and selecting exactly the color of the stained glass that he wishes to use in his artwork. A slot in the middle of the board allows a more expensive type of cutter as well as the less expensive glass cutter to score and glide easily from bottom to top or top to bottom (as some artisans prefer) and effectively score a straight line on the glass. The slot also prevents slipping to the side as would be true when using a straight edge or T square and allows for a stronger and more rigid scoring. The scoring board also has topside and underside rubber strips to prevent slippage, as would be true when using a straight edge, allowing for the effective scoring of horizontal and vertical lines and to diminish wear and tear to the cutter's carbide wheel.

Abstract: A stereotactic auxiliary attachment for a tomography apparatus for conducting a tomogram-guided biopsy of an examination subject has two compression plates for fixing the examination subject therebetween, with through-holes arranged in each compression plate enabling a guided access of a biopsy needle. An optical marking system is provided which optically marks the through bore most suitable inserting and guiding the biopsy needle for the biopsy, after the location of the lesion has been identified in a tomogram.

Abstract: Two Sagnac interferometers are mounted on board a ship with their axes in a horizontal plane. The axis of one interferometer is aligned in a fore-aft direction whereas the axis of the other interferometer is aligned athwartship. The output signals of the two interferometers are combined mathematically so as to cancel the effects of the ship's latitude and thus provide an output signal independent of this parameter.

Abstract: A geometrical instrument for use with a straight edge to mark positions on a flat surface is described. The instrument has a receiver slot on its rear side. The receiver slot extends the width of the instrument such that the instrument can be slideably mounted on the straight edge, The instrument includes a holder to position a writing implement above the receiver slot such that the writing implement marks the flat surface. The instrument also includes a positioning hollow with a centering point aligned with the center of the holder. Additionally, the instrument may include a slot for inserting a knife blade.

Abstract: A jig which receives a sheet in a selected position to accurately scribe it in a straight line. The jig has front and rear panels which form a vertical slit between them in which the sheet is received. The bottom of the sheet sits on an elongated support bar which extends horizontally in the slit and the line is scribed by running a scribing tool along the upper scribing edge of the front panel. The support bar has a pair of spaced studs which extend out through matching openings in the front panel to allow the support bar to be manually moved between a number of different vertical positions to select the distance the line is scribed from the bottom of the sheet. The openings in the front panel each have a number of spaced slots extending sideways which provide a pair of notches in which the studs are seated in each position. The studs are threaded to receive a retaining knob which are tightened against the front panel to secure the support bar in the selected position.

Abstract: A strapped down astro-inertial navigator includes a roll outer gimbal, a pitch inner gimbal and a platform coupled to the inner gimbal. An instrument cluster which includes X-axis, Y-axis and Z-axis ring laser gyros (RLGs) and associated accelerometers is mounted to the platform. Also hard mounted to the platform is a stellar sensor which includes a telescope and a solid state focal plane array which views stellar reference objects. In an astro-inertial mode of operation one or more stellar objects are tracked for a period of time. The roll and the pitch gimbals are employed to point the telescope and, periodically, to observe and average out the effects of star sensor and horizontal accelerometer errors. The star sensor error observability is accomplished by periodically rotating the inner and outer gimbals through 180.degree. and the stellar objects once again tracked. Due to the 180.degree. rotation boresight errors within the stellar tracker are observed and compensated for. The 180.degree.

Abstract: Disclosed is a northfinding apparatus having a single rotation rate sensor secured to a platform. The output of the rotation rate sensor is corrected for tilt and tilt rate of the platform. Measurements of the tilt and tilt rate and the rotation rate are combined to provide an azimuth angle of the platform relative to north.

Abstract: A slicing guide marker for marking impressionable food products with an elongated cantilever arm rotatably attached to a support shaft. The cantilever arm having a marking roller adjacent one end and a counterweight slidably carried by the arm. The marking roller having a wheel with a plurality of teeth extending generally radially outwardly of the wheel for marking the food product.

Abstract: The calibration of time-depending measurement uncertainties of gyros and inertial systems by the differences of angular and/or velocity and/or positional measurements which are carried out and repetitiously executed with a view to undetermined reference directions and/or fixed locations varying with time. The differentiation allows to forego precise reference data. Measurement uncertainties can be corrected through calibration subsequently to the measurement process. For the measurement of spatial angles a three-axis gyro measurement package comprising a computer and the possibility of feeding or automaticly reading-in of reference data characterizing the reference directions. The reference data can be a number, a marker of the measurement point or in the case of positional measurements a terrestrial aiming point. When measuring angular characteristics, i.e. the interdependence of angles and external forces or moments, the latter are considered as references.

Abstract: A fault-tolerant air data and inertial navigation reference system utilizes skewed axis inertial sensors and fault-tolerant redundant electronics to provide higher redundancy with fewer parts. Parallelly operating processor circuits each receive the individual outputs of six skewed-axis gyros and six skewed-axis accelerometers. Each processor independently processes parity equations using the outputs to identify malfunctioning sensors. Further, the output of each processor is transmitted to three parallelly operating voter circuits. The voters are operable to discard a processor if its output does not agree with the majority. The voter outputs are similarly fed back to the processor circuits, which compare these outputs, and discard any voter whose output disagrees with the majority, thus providing a completely integrated system.

Abstract: A support assembly includes a base having end edges along which extend toothed racks for engagement of a clamping bar having meshing detents on its end portions, the clamping bar providing a guide track for a DIY mat cutter. The base is invertible to present English system and metric system distance-measuring features on its opposite side surfaces.