Constant altitude plan position indicator for radars

• US 20060202884A1
• Filed: 09/26/2005
• Published: 09/14/2006
• Est. Priority Date: 03/10/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Mahapatra, Pravas R., Makkapati, Vishnu V.
• Granted Patent: US 7,646,328 B2
• Time in Patent Office: Days
• US Class Current: 342/26.R
• CPC Class Codes: G01S 13/95 for meteorological use
• CPC Class Codes: G01S 7/12 Plan-position indicators, i.e. P.P.I.
• CPC Class Codes: G01S 7/18 Distance-height displays; Distance-elevation displays, e.g. type RHI, type E
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

A method and a system to process radar volume scan data along an azimuth angle of a radar, to interpolate the radar volume scan data taken from adjacent elevation angles along the azimuth angle of the radar to obtain radar data corresponding to a predetermined altitude along the azimuth angle, and to display the radar volume scan data obtained corresponding to the predetermined altitude on a PPI display.

Claims

1. A method to display weather radar data comprising:

processing radar volume scan data along an azimuth angle of a radar;

interpolating the radar volume scan data taken from adjacent elevation angles along the azimuth angle of the radar to obtain weather radar data corresponding to a predetermined altitude along the azimuth angle; and

displaying the weather radar data obtained corresponding to the predetermined altitude on a two-dimensional display.

2. The method of claim 1 further comprising processing the radar volume scan data along a plurality of azimuth angles to obtain radar Constant Altitude Plan Position Indicator (CAPPI) scan line data corresponding to the predetermined altitude.

3. The method of claim 2 further comprising processing the radar volume scan data along one of the plurality of azimuth angles from a minimum azimuth angle to a maximum azimuth angle to obtain the radar CAPPI scan line data corresponding to the predetermined altitude.

4. The method of claim 2 further comprising generating CAPPI scan line data over a predetermined distance interval from the radar.

5. The method of claim 1 further comprising determining a distance from a vertical at a location of the radar along a constant-altitude surface associated with the predetermined altitude to an intersection with a predetermined elevation angle from the radar location.

6. The method of claim 5 further comprising determining two adjacent elevation angles in a radar volume scan data set for any given point on the constant-altitude surface.

7. The method of claim 6 further comprising determining weights for averaging data from the adjacent elevation angles based on the distance from the vertical.

8. The method of claim 7 further comprising calculating the weights and corresponding ranges at the predetermined altitude using at least one of a graph, a chart, a table, an algorithm, and a set of equations.

9. The method of claim 1 wherein interpolating includes using a weighted average interpolation mechanism, wherein the mechanism includes at least one of a graph, a chart, a table, an algorithm and a set of equations.

10. The method of claim 1 further comprising converting between spherical coordinates of the radar volume scan data and geocentric spherical coordinates.

11. A computer-readable medium having program instructions to perform a method to display weather radar data, the method comprising:

processing radar volume scan data along an azimuth angle of a radar;

interpolating the radar volume scan data taken from adjacent elevation angles along the azimuth angle of the radar to obtain weather radar data corresponding to a predetermined altitude along the aximuth angle; and

displaying the weather radar data obtained correspondence to the predetermined altitude on a two-dimensional display.

12. A process of generating CAPPI data at a point C having an altitude H along an azimuth angle θ

, the process comprising;

calculating arc length EC(φ

_m) for each elevation angle φ

_m of a radar using EC(φ

_m)=(R_e+H)×

[cos<sup>−

1</sup>(R_e cos(φ

_m)/(R_e+H))−

φ

_m], where m includes an elevation number, where 0≦

m≦

M, where M−

1 includes a number of elevation scans performed by the radar, where R_e includes the radius of the earth, and H includes the altitude at which CAPPI data is to be generated;

generating a first technique of EC(φ

_m) values indexed by a group selected from the elevation number m and the elevation angle φ

_m of the radar;

determining the elevation angle φ

for arc length EC at each determined increment along the arc EC from EC(φ

_M) to EC(φ

₀) using φ

=tan<sup>−

1</sup>[((R_e+H)cos(β

)−

R_e)/((R_e+H)sin(β

))], where β

=(EC)/(R_e+H);

determining, at each incremented arc length EC in an interval 0<

EC<

EC(φ

_M-1), a weight AC using weight AC=CD×

sin(φ

−

φ

_M-1)/(cos(φ

_M-1+β

), where CD=√

{[(R_e+H)sin(β

)]²+[(R_e+H)cos(β

)−

R_e]²}, and calculating a range line DA for the domain [0;

EC(φ

_M-1)] by solving equation

$\frac{1}{17000}<br><br>{\left(\mathrm{DA}\right)}^2<br><br>{\cos }^2<br><br>\left({\mathrm{\varphi <br><br>}}_{M-1}\right)+\left(\mathrm{DA}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\left({\mathrm{\varphi <br><br>}}_{M-1}\right)=H-\left(\mathrm{AC}\right);<br><br>$

determining, at each incremented arc length EC in an interval EC(φ

_M-1)<

EC<

EC(φ

₁), lengths BC and AC, respectively corresponding to elevation angles φ

_m and φ

_m-1 adjacent to elevation angle φ

, where length BC=CD×

sin(φ

_m−

φ

))/(cos(φ

_m+β

) and length AC=CD×

sin(φ

−

φ

_m-1)/(cos(φ

_m-1+β

), calculating a range DB for the domain [EC(φ

_M-1);

EC(φ

₁)] from the radar to a point B vertically above the point C along the azimuth angle θ

by solving equation

$\frac{1}{17000}<br><br>{\left(\mathrm{DB}\right)}^2<br><br>{\cos }^2<br><br>\left({\mathrm{\varphi <br><br>}}_m\right)+\left(\mathrm{DB}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\left({\mathrm{\varphi <br><br>}}_m\right)=H+\left(\mathrm{BC}\right),$

and calculating the range line DA for the domain [EC(φ

_M-1);

EC(φ

₁)] from the radar to a point A vertically below the point C along the azimuth angle θ

by solving equation

$\frac{1}{17000}<br><br>{\left(\mathrm{DA}\right)}^2<br><br>{\cos }^2<br><br>\left({\mathrm{\varphi <br><br>}}_{m-1}\right)+\left(\mathrm{DA}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\left({\mathrm{\varphi <br><br>}}_{m-1}\right)=H-\left(\mathrm{AC}\right);<br><br>$

and

calculating, in an interval EC(φ

₁)<

EC<

EC(φ

₀), a weight BC using weight BC=CD×

sin(φ

₁−

φ

)/(cos(φ

₁+β

), and calculating the range DB for the domain [EC(φ

₁);

EC(φ

₀)] by solving equation

$\frac{1}{17000}<br><br>{\left(\mathrm{DB}\right)}^2<br><br>{\cos }^2<br><br>\left({\mathrm{\varphi <br><br>}}_1\right)+\left(\mathrm{DB}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\left({\mathrm{\varphi <br><br>}}_1\right)=H+\left(\mathrm{BC}\right).$

13. The process of claim 12 further comprising generating a second technique containing the range line DA indexed by arc length EC for the domain [0:

EC(φ

_M-1)].

14. The process of claim 13 further comprising generating a third technique of weights BC and AC indexed by arc length EC for the domain [EC(φ

_M-1);

EC(φ

₁)].

15. The process of claim 13 further comprising storing in the second technique, for the domain [EC(φ

_M-1);

EC(φ

₁)], the range DB and the range line DA indexed by arc length EC.

16. The process of claim 13 further comprising storing in the second technique, for the domain [EC(φ

₁);

EC(φ

₁)], the range DB indexed by arc length EC.

17. The process of claim 14 wherein the first, second and third techniques are selected from a group including an algorithm, a chart, a table, a graph, and an equation.

18. The process of claim 12 further comprising:

retrieving radar data Z_A for the domain [0;

EC(φ

_M-1)] at the range line DA from a radar volume scan data at the elevation angle φ

_M-1 and setting radar data Z_C to radar data Z_A;

retrieving radar data Z_A and Z_B at the range lines DA and DB, respectively, for the domain [EC(φ

_M-1);

EC(φ

₁)], from the radar volume scan data at two elevation angles φ

adjacent to the point C, and calculating CAPPI data Z_C at the point C using equation

$Z_C=\frac{\left(\left(\mathrm{BC}\times <br><br>Z_A\right)+\left(\mathrm{AC}\times <br><br>Z_B\right)\right)}{\left(\mathrm{BC}+\mathrm{AC}\right)};<br><br>$

and

retrieving radar data (Z_B) at the range DB, for the domain [EC(φ

₁);

EC(φ

₀)], from the radar volume scan data at the elevation angle φ

₁ and setting radar data Z_C to radar data Z_B for the domain [EC(φ

₁);

EC(φ

₀)].

19. The process of claim 18 further comprising:

setting arc length EC to a minimum distance EC_min;

setting the increment associated with the arc length EC, Δ

EC, to 1 km;

setting an azimuth angle increment Δ

θ

to 1°

;

setting azimuth angle θ

to a starting azimuth angle θ

_min; and

querying whether θ

≧

an ending azimuth angle θ

_max.

20. The process of claim 19 wherein if θ

<

θ

_max, then CAPPI data at point C is generated at the azimuth angle θ

, and the azimuth angle θ

is set to 0+Δ

θ

.

21. The process of claim 19 wherein if θ

≧

θ

_max, and the arc length EC<

EC (0°

), then the azimuth angle θ

is reset to the starting azimuth angle θ

_min, and the arc length EC is set to EC+Δ

EC.

22. The process of claim 12 wherein the mechanism includes a group selected from a graph, a chart, a table, an algorithm and a set of equations.

23. The process of claim 12 wherein the mechanism is generated by a processor using radar volume scan data obtained from a group selected from data obtained in real-time and data retrieved from storage.

24. The process of claim 12 wherein each of the range lines DB and DA include curves representing bent propagation paths between the radar and the points B and A, respectively.

25. The process of claim 18 further comprising displaying the CAPPI data generated at the altitude in a PPI display.

26. The process of claim 25 wherein the PPI display supports an application selected from a group including rotation, zooming, magnification, distance interval, and sector selection.

27. A system to display weather radar data comprising:

means for processing radar volume scan data along an azimuth angle of a radar;

means for interpolating the radar volume scan data taken from adjacent elevation angles along the azimuth angle of the radar to obtain CAPPI data corresponding to a predetermined altitude along the azimuth angle;

means for performing the above two steps for the azimuth angles within a specified range; and

means for displaying the CAPPI data obtained corresponding to the predetermined altitude.

28. The system of claim 27 further comprising means for generating CAPPI data from repeatedly performed similar radar volume scans by the radar.