Sensor Field Of View Research Articles

Improvements in coverage frequency of ocean color: combining data from SeaWiFS and MODIS

Large improvements in coverage frequency (daily to four-day) can be expected by combining ocean color data from the Sea-Viewing Wide Field Of-View Sensor (SeaWiFS) and Moderate Resolution Imaging Spectrometer (MODIS) missions. Results indicated 40-47% increases in global coverage over SeaWiFS alone in one day and >100% in low latitudes. The missions are highly complementary for observation of short-term processes.

A survey of sensor planning in computer vision

A survey of research in the area of vision sensor planning is presented. The problem can be summarized as follows: given information about the environment as well as information about the task that the vision system is to accomplish, develop strategies to automatically determine sensor parameter values that achieve this task with a certain degree of satisfaction. With such strategies, sensor parameters values can be selected and can be purposefully changed in order to effectively perform the task at hand. The focus here is on vision sensor planning for the task of robustly detecting object features. For this task, camera and illumination parameters such as position, orientation, and optical settings are determined so that object features are, for example, visible, in focus, within the sensor field of view, magnified as required, and imaged with sufficient contrast. References to, and a brief description of, representative sensing strategies for the tasks of object recognition and scene reconstruction are also presented. For these tasks, sensor configurations are sought that will prove most useful when trying to identify an object or reconstruct a scene. >

Parameter estimation for gray and nongray targets: theory and data analysis

A new technique is described that can be used to estimate basic parameters such as target size (projected area), surface temperature, and spectral emissivity based on the optical radiation measured by a multiband infrared radiometer. This is of great interest in science and industry where the ability to measure temperature and surface optical characteristics via noncontact methods is vital to the analysis and control of many processes. This new technique is designed to compensate for reflected radiation from other background sources not in the sensor field of view. The technique is based on applying a simple closed form expression for the optical signal measured by the sensor and expanding the unknown emissivity in a series of orthogonal functions. To obtain the parameters of interest nonlinear least-squares estimation techniques are employed. To test the overall procedure data were collected on targets specifically designed to span the range from gray to highly nongray. The optical radiation from these targets was measured in a ground-based space simulation chamber in the presence of known and controlled warm background sources. The targets were instrumented with thermocouples that measured the surface temperature throughout the experiment. Results of the data analysis show that, using a three- or four-band radiometer, it is possible to measure surface temperature to a high degree of accuracy, and that the technique is robust in the presence of noise. Other applications are also explored. These include the simultaneous estimation of the target size (projected area) for point targets at a known distance from the optical sensor, as well as a detailed estimate of the material spectral emissivity using data provided by a spectrometer.

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. >

Automatic sensor placement from vision task requirements

The problem of automatically generating the possible camera locations for observing an object is defined, and an approach to its solution is presented. The approach, which uses models of the object and the camera, is based on meeting the requirements that: the spatial resolution be above a minimum value, all surface points be in focus, all surfaces lie within the sensor field of view and no surface points be occluded. The approach converts each sensing requirement into a geometric constraint on the sensor location, from which the three-dimensional region of viewpoints that satisfies that constraint is computed. The intersection of these regions is the space where a sensor may be located. The extension of this approach to laser-scanner range sensors is also described. Examples illustrate the resolution, focus, and field-of-view constraints for two vision tasks. >

The Effect of Directional Radiation Models on the Interpretation of Earth Radiation Budget Measurements

A parameter estimation technique is presented to estimate the radiative flux density distribution over the earn from a set of radiometer measurements at satellite altitude. The technique analyzes measurements from a wide field of view, horizon to horizon. nadir pointing sensor with a mathematical technique to derive the radiative flux density estimates at the top of the atmosphere for resolution elements smaller than the sensor field of view. A computer simulation of the data analysis technique is presented for both earth-emitted and reflected radiation. The errors resulting from the assumed directional radiation model, spatial model and random measurement error have little effect an the global mean radiation. Zonal estimates were found to be more sensitive, to the spatial model than to the directional radiation model. Results from analysing medium field of view measurements showed a much greater sensitivity to the directional radiation model, even on a global scale.

Line Criteria in Target Acquisition with Television

This paper presents a review of experimental data from tests of target acquisition with electro-optical, raster scan systems. These data, as well as equipment parameters such as sensor field of view, system line number, display size, and target size on the display, can be used to estimate target acquisition performance by system operators. The paper lists the equations required to make such performance estimations, and several examples are given. The procedure can be used to compute equipment characteristics required to insure prescribed levels of target acquisition performance.