Michael F. Gard

A status report on environmental monitoring

Environmental issues receive increasingly greater attention in the technical, scientific, and popular press. On a global scale, sophisticated measurements are available using satellite-based instruments. This type of monitoring is known as remote sensing, a topic not covered in this paper. This paper discusses the social/political forces which determine environmental monitoring on a more immediate local level, the implementation areas typified by industrial, agricultural, and environmental sampling applications, and briefly touches on technological advances bringing new techniques and capabilities to the solution of environmental monitoring problems. Because the topical area is very broad, any survey treatment of it must necessarily omit many details. This paper is intended to provide information introducing environmental monitoring as it now exists and to suggest opportunities for participation in environmental work.

Analytical and simulated signal prediction for a collimated point sensor using a surface emission model

Simulation of IR measurements from an arbitrary emitting body is complicated by the fact that measured energy is emitted only from the objects surface. A two-dimensional model of collimated measurements is derived and compared to an unusual signal estimation algorithm based on a sorting procedure. Mathematical development yields a two-dimensional analytical expression providing the response of a collimated omnidirectional point sensor to a general straight-line emitter in an attenuating medium with a constant attenuation coefficient. The analytical response has been used to predict sensor responses to various synthetic images representing idealized cross-sections of intruding heated material. Agreement between analytical predictions and simulations from synthetic images is very good.<<ETX>>

Optical Measurement of Angular Deformation and Torque Inside a Working Drillstring

This paper describes apparatus capable of angular rotation measurements needed to calculate torque applied to a horizontal directional drilling (HDD) drillbit. Measurements are made using a solid-state imager (camera), a single lens, and a special optical target having precision circular apertures. This apparatus is unusual in that it is mounted inside the drillstring housing being measured, for HDD applications are not compatible with conventional externally mounted measurement devices. The measurement approach uses signal centroid calculations associated with image features rather than pattern matching or other standard image analysis techniques.

Real-time X-ray fan-beam z-axis position measurement

The control of fan beam z-axis position is important for the production of highest-quality computerized tomography (CT) images. The authors describe a special measurement technique that produces an accurate real-time analog measurement of the fan beam z-axis position using a set of triangular masks over conventional detector cells. Data obtained from the masked detector cells are normalized to make the position signal independent of radiological dose and collimator aperture setting. The resulting position signal is ideally suited for closed-loop fan beam position control. >

Image formation from severely undersampled scalar infrared data sets

The author describes the formation of an image from no more than ten (and usually fewer) scalar sensor readings. An infrared (IR) signal source is assumed, placing unusual demands on signal estimation and image construction algorithms. An onion-growth image construction algorithm that generates a single binary image object consistent with sensor measurements is presented. It is so called because it identifies an approximate center of mass, or seed pixel, and then grows a series of concentric circles around the seed pixel. Synthetic object studies illustrate the effectiveness of the image construction algorithm and demonstrate that, image artifacts are suppressed or eliminated by using the largest possible sensor field of view. >