Predictive and adaptive weather radar detection system and method

A method of detecting weather on an aircraft uses a weather radar system. The method includes determining a location of a reflective radar target, accessing a database having stored information relating to ground clutter of a reflective radar target, retrieving weather radar information associated with the location, and automatically adjusting the weather radar return threshold in response to the information. The method can adjust a threshold for a weather radar display, adjust a weather radar signal gain, adjust a tilt angle of the weather radar, or adjust a ground clutter suppression threshold. The method can be implemented by hardware and/or software.

BACKGROUND

Conventionally, pilots use weather radar to detect and avoid hazardous weather. Conventional radar systems may produce the desired results only in a limited environment. Typically, airborne threshold systems use thresholds for wet precipitation derived from ground-based weather radar thresholds which were generated from convective weather detections. Such thresholds have been set in accordance with reflectivity data which is applicable to typical convective weather systems. It has been observed that for airborne applications ground clutter causes differences in reflectivity which may cause inaccurate weather indications. A feature of conventional radar systems is the ability to suppress display of returns from the ground in favor of returns from weather. These ground clutter suppression systems may have limited effectiveness with certain local geographical conditions, such as in the presence of cities, especially cities near bodies of water, and with tall objects, such as towers beyond the horizon. Such ground clutter may erroneously be presented as a weather target. Conventionally, weather radar ground clutter suppression systems may rely on different return signals resulting from radar beam sweeps occurring at different beam elevations. Even so, many geographical phenomena may not be suppressed using present ground clutter suppression systems.

Conventionally, radar thresholds map radar return strength to a display with color representing rain rate or alternatively a weather threat assessment level. The threat level has been previously described as primarily a function of radar reflectivity and a weaker function of temperature, altitude, and latitude. However, because of various geographical phenomena, the conventional mapping, while useful, does not completely allow successful operation of aircraft in difficult geographic situations. The higher reflectivity of these geographic phenomena produces erroneous detection of significant convective weather systems during flight. Further, because of the ability of aircraft flying over such geographical phenomena to circumnavigate storm systems, when believed to be present, it would therefore be desirable to provide an airborne radar system which has the ability to more accurately detect and report the existence and/or characteristics of storms when operating in various geographically diverse environments.

It may be possible for a pilot operating a radar manually to be able to compensate for the differences in geographical phenomena as each pilot becomes familiar with the environment. However, knowledge by the pilot must be acquired, and further, an increase in pilot workload is also necessitated. Therefore, there is a need for an automated system of adjusting radar thresholds based on the presence of a variety of geographical phenomena.

In addition, ground clutter reflectivity can vary by time of day and time of year, in various geographical regions. For example, dew forming on grass increases ground reflectivity. Ground reflectivity also may vary depending on whether forests are leaf covered or bare or whether fields are filled or fully vegetated. Similarly, snow covered landscapes reflect differently than green grasslands. Thus, it may be desirable to identify ground clutter in accordance with temporal information.

In addition, weather characteristics can change according to seasonal and time-of-day variations. For example, certain radar reflectivities occurring during the monsoon season may indicate hazardous weather while those same radar reflectivities would indicate non-hazardous weather during another season. Similarly, weather radar returns at a certain time-of-day are more likely to indicate the presence of hazardous weather (e.g., afternoon) while those same returns are less likely to indicate the presence of a hazard at another time-of-day (e.g., early morning). Accordingly, it would be desirable to provide a radar system which can compensate radar detection in accordance with both temporal and spatial information.

Accordingly, there is a need to adjust weather radar detection and ground clutter suppression schemes based upon a specific geographic location, time-of-day, and/or season (time-of-year). There is further a need to adjust weather radar systems by adjusting display thresholds, tilt angle, and/or system gain. Yet further, there is a need for a weather radar system that automatically adjusts to location time-of-day, and/or time-of-year. Yet further still, there is a need to adjust weather radar systems by adjusting thresholds and parameters based on known ground clutter locations.

It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.

SUMMARY

An exemplary embodiment relates to a method of detecting weather on an aircraft using a weather radar system. The method includes determining a location of reflective radar targets, accessing a database having information relating to ground clutter of the reflective radar targets, retrieving weather radar information associated with the location and automatically adjusting the weather radar return thresholds in response to the information.

Another exemplary embodiment relates to a method of adapting an aircraft weather radar system. The method includes determining at least one of a time-of-year parameter, a time-of-day parameter, or a location parameter. The method also includes automatically adjusting the weather radar system radar return display thresholds to display weather in response to at least one of the time-of-year parameter, time-of-day parameter, or location parameter.

Still another exemplary embodiment relates to an airborne weather radar system carried on an aircraft. The airborne weather radar system includes a radar antenna system and a processing means for adjusting display thresholds of the weather radar system. The processing means adjusts performance of the weather radar system based on a location of known ground clutter targets.

Yet still another exemplary embodiment relates to a method of creating a weather radar display threshold database. The method comprises receiving, by a ground-based weather radar system, weather radar returns for a location. The method also comprises receiving by an airborne based weather radar system weather radar returns over the location. Further, the method comprises determining a display threshold for the airborne based weather radar system which provides a substantial match of the ground-based weather radar returns and the airborne based weather radar returns.

DETAILED DESCRIPTION

Before describing in detail the particular improved system and method, it should be observed that the invention includes, but is not limited to a novel structural combination of conventional data/signal processing components and circuits, and not in the particular detailed configurations thereof. Accordingly, the structure, methods, functions, control and arrangement of conventional components and circuits have, for the most part, been illustrated in the drawings by readily understandable block representations and schematic diagrams, in order not to obscure the disclosure with structural details which will be readily apparent to those skilled in the art, having the benefit of the description herein. Further, the invention is not limited to the particular embodiments depicted in the exemplary diagrams, but should be construed in accordance with the language in the claims.

In conventional aircraft systems, radar systems attempt to detect weather which may be a threat to the aircraft or passengers. However, in environments in which ground clutter or other ground reflectivity effects are pronounced, the radar systems may misidentify ground as threatening weather. As a result, air carriers attempt to circumvent weather systems which are nonexistent and thereby waste precious fuel and time.

Radar ground clutter suppression is hampered by local geographical phenomena. For example, cities near bodies of water and tall objects such as radio towers beyond the horizon sometimes violate the assumptions made during the design of general ground clutter suppression algorithms. The result is that ground clutter leaks through the suppression algorithms and is erroneously presented to the pilot as a weather target.

Conventional radar ground clutter suppression algorithms rely on the vertical gradient of the return signals resulting from multiple radar sweeps occurring at different beam elevations. The ground clutter suppression algorithms and beam tilt algorithms are designed to reject clutter under a wide variety of conditions. Unfortunately, some geographic phenomena may defeat the generally optimized algorithm, resulting in ground clutter being presented to the pilot as weather. This issue has been observed in many conventional systems.

The trade-off which normally occurs during design of ground clutter suppression algorithms is between ground clutter suppression and weather detection. Further increase in the radar's ability to provide accurate ground clutter suppression will result in an overall decrease in the radar's ability to perform its primary function of weather detection. Much of the observed ground clutter leakage is localized and is tied to understood phenomena. For instance, ground objects with very high reflectivity located near relatively low reflective bodies of water may defeat the conventional ground clutter suppression algorithms. The highly reflective city of Chicago located on the shore of Lake Michigan is a prime example. A general modification of the ground clutter suppression algorithm to eliminate ground clutter leakage from the Chicago point target would unacceptably decrease the radar's ability to detect weather across the entire radar display area.

Localized threshold optimization methods may be used to improve weather radar ground clutter suppression algorithms. The weather radar may contain a local terrain database which is currently used to determine optimal tilt angle. This database can also be tagged with localized clutter suppression/weather detection threshold information which can be processed to minimize the probability of ground clutter leakage over specific geographical areas. Even though the threshold over such “problem” areas can be locally tuned to favor ground clutter suppression, weather detection over such areas will actually be improved since it is impossible to accurately display weather phenomena over areas where ground clutter is actively leaking onto the display.

The position of the aircraft relative to the “problem” geographical feature can be used to qualify the use of the threshold information. The tops of tall, reflective objects such as weather towers poke above the horizon and result in ground clutter leakage. These objects are only a problem when they lie at a specific distance from the aircraft. Specific phenomena such as weather towers can be tagged as “horizon-only” problems and local optimization of clutter thresholds can occur based on their position relative to the local horizon.

Previous approaches to ground clutter suppression involved various algorithms including, but not limited to active editing of return data. Such editing is done by accessing a terrain database and identifying areas of typically higher reflectivity and removing any radar returns from that area. The key techniques, methodologies, and systems provided herein are an improvement over editing of radar returns.

Referring toFIG. 1, an aircraft100is depicted having a radar on-board capable of casting a radar beam190and receiving reflective energy from weather systems125,130,135, and the like. Weather systems125,130, and135may be representative of any variety of weather systems. Convective weather system130may be over a city140having a plurality of buildings142. City,140may be on the shores of a major body of water145.

Referring now toFIG. 2, a radar system200includes a radar antenna210for sending and receiving radar signals. System200also includes an adjustable gain circuit220that is configured to change the gain of the radar signal provided to or received from radar antenna210. Processing device230receives time and date data from time/date sensor240and radar tilt sensor250, among other systems and sensors. Further, processing device230receives location data from an aircraft location sensor245, such as but not limited to a GPS receiver. In an exemplary embodiment, processing device230also accesses a database260which contains information relating to known ground clutter locations based on the location of the aircraft. Processing device230may also be configured with instructions which calculate and/or determine an appropriate adjustable threshold command via a control law which is based on the location of the aircraft, the known ground clutter location, the time-of-day, the time-of-year, etc. The adjustable threshold command is to be communicated to an adjustable threshold circuit232based on data supplied to processing circuit230such as but not limited to the locations of the aircraft, locations of known ground clutter, time-of-day, time-of-year, temperature inputs, and the radar beam direction. As shown, adjustable threshold circuit232is running on processor230, however adjustable threshold circuit is not limited to the depicted structure but may be running on a different processor or a dedicated circuit or processor. Further, other information such as latitude, longitude, maritime, or continental, etc. may also be used to make the gain adjustment. Database260may be used to describe whether a specific location (i.e., latitude, longitude) is near a known ground clutter target. The database may be generated from a table of altitudes versus latitude/longitude.

A threshold control law used in adjustable threshold circuit232may be based on any of a number of factors, including but not limited to the location of the aircraft, the location of ground clutter, the location of bodies of water, the time-of-day, the time-of-year, etc. The thresholds may be adjusted according to these characteristics using adjustable threshold circuit232, and thereby display, on display234, the appropriate weather-hazard alert or condition. Other types of alerts may also be used and be based on the adjustable thresholds, including but not limited to visual and aural warnings. In an exemplary embodiment, location, time, date, etc. may be used to predict ground reflectivity so ground clutter can be suppressed. Also, in an exemplary embodiment, location, date, time, etc. may be used to adjust thresholds to more accurately depict weather hazards.

In accordance with an exemplary embodiment, any type of weather radar that operates in a range of environments may be used. This includes, but is not limited to simple auto-tilt radars, manual radars, as well as fully automatic systems including but not limited to the WXR-2100 multiscan radar available from Rockwell Collins of Cedar Rapids, Iowa.

In an alternative embodiment, system200may be used to control antenna tilt, gain control on the receive side, gain control on the transmit side, as well as thresholds.

The database may be used to bias the threshold process, the gain control process, or antenna tilt. Antenna beams which impinge on known ground clutter have their effective gain reduced during sampled ranges that have that interaction. This allows known ground clutter to not be displayed to the pilot and allows increased weather detection characteristics in areas of typically high reflectivity. The gain reduction system differs from an editing system in that boundary values may be softened to reduce the effects of identification mistakes and still allow weather detection in the area influenced by land, island, or mountain targets.

In a similar manner, the thresholds used in multibeam clutter rejection processes may be modified by using the database to improve weather detection margins and improve clutter removal robustness. This may allow lower antenna beam angle to interrogate weather while providing clutter rejection for precipitous terrain.

With reference toFIG. 3, weather radar system300is similar to system200described above. System300may utilize any type of base hardware including the hardware associated with conventional weather radar systems manufactured by Rockwell Collins, Inc. and Honeywell International. System300is advantageously configured to automatically adjust to a particular location parameter, time-of-day parameter, and/or season parameter.

The location parameter can provide a precise latitude and longitude, a general area, a distance along a flight plan or other type of location indicator. The location parameter can be provided by any type of location sensor including but not limited to a GPS system. The location parameter can also be provided from an off-airplane source or be derived from flight plans and time-of-flight parameters.

System300preferably includes a tilt control circuit304, a radar antenna301, a receive transmit circuit308, a memory303, a location circuit312, a clock circuit314, a date circuit316, a display306, and a processor305. Processor305may include a display threshold adjustment circuit324. Circuit324may operate in accordance with the description provided above. Gain control circuit309can operate on the receive end or the transmit end. Preferably, gain control circuit309operates on the transmit end and is controlled by a signal from processor305or alternatively operates in processor305.

In an alternative embodiment, the location parameter can indicate a specific region having a predetermined target area. For example, the location parameter can be any area, but typical examples would be in the range of a several square mile region. The size and/or borders of regions can change as a function of location, time-of-day, and/or season.

Clock circuit314provides an indication of time-of-day to processor305. Date circuit316provides a time-of-year indication to processor305. Although shown as coupled directly to processor305, circuits312,314, and316can be incorporated within processor305and can even be provided wholly or at least partially as a software sub-routine. In addition, circuits312,314,316can communicate with processor305through memory303. Processor305does not need to communicate through memory303and can communicate directly with receive/transmit circuit308.

Processor305can provide control signals to tilt control circuit304and gain control circuit309. System300can be adjusted through processor305to take into account a location parameter from circuit312, a time-of-day parameter from circuit314, and a time-of-year parameter from circuit316. Processor305preferably automatically adjusts at least one of display threshold circuit324, tilt control circuit304, and gain control circuit309. The adjustment preferably makes the sensing of weather regions and their severity more accurate and allows more accurate removal of ground clutter. Gain control circuit309can control the gain associated with the transmit end or the receive end of signals provided to and from antenna301.

Antenna controlled elevations, radar gains, weather detection thresholds, and ground clutter rejection thresholds can also be a function of time-of-year and time-of-day. As an example of time-of-year adjustments, consider the changes in ground reflectivity with changes in snow cover and grass cover, seasonal changes in forest foliation and defoliation, etc. An example of time-of-day adjustment may involve the presence of dew causing increased reflectivity during early morning, etc.

With reference toFIG. 4, a flow diagram400depicts the operation of circuit300. Processor305preferably operates software to implement flow diagram400. A location parameter, time-of-day parameter, and/or seasonal parameter is determined (process410). The antenna tilt is then adjusted in accordance with the parameter or the gain is adjusted in accordance with the parameter (process420). Radar return thresholds, display thresholds, and/or ground clutter rejection thresholds may also be adjusted based on the parameters to support the ground clutter rejection (process430) and to optimize weather detection. Processor305processes radar returns (process440). Processor305then provides indications of hazards and/or weather on display306(process450).

With reference toFIG. 5, a flow diagram500depicts operation of system300in accordance with another embodiment. Processor305preferably operates software to implement flow diagram500. A location parameter, time-of-day parameter, or seasonal parameter is determined (process510). Radar returns are processed in processor305(process520). The threshold associated with the display of hazards or weather is adjusted (process530). Indications of hazards and/or weather are then displayed on display306(process540). Thresholds may be adjusted on a complete radar sample environment or on a radar resolution cell by radar resolution cell basis. In one embodiment, thresholds preferably slew smoothly from space/time region to space/time region with step changes preferably not being allowed.

Referring now toFIG. 6, a method600of creating a weather radar display threshold database comprises receiving weather radar returns from ground-based weather radar from a location (process610). The method also comprises receiving weather radar returns from an airborne based weather radar over a location (process620). Once the weather radar returns have been received, a comparison may be made of the airborne and ground based weather radar returns (process630). Once this comparison is accomplished a substantial match of the airborne based returns and the ground-based returns may be made by providing display thresholds (process640). In accordance with other exemplary embodiments, a plurality of learning systems may be applied in order to determine the display thresholds needed to achieve, in an optimal manner, the matching airborne based weather radar returns being displayed.

While the detailed drawings, specific examples and particular formulations given describe preferred and exemplary embodiments, they serve the purpose of illustration only. The inventions disclosed are not limited to the specific forms shown. For example, the methods may be performed in any of a variety of sequence of steps. The hardware and software configurations shown and described may differ depending on the chosen performance characteristics and physical characteristics of the radar system devices. For example, the type of device, communications bus, or processor used may differ. The systems and methods depicted and described are not limited to the precise details and conditions disclosed. Furthermore, other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the exemplary embodiments without departing from the scope of the invention as expressed in the appended claims.