Methods and systems for estimating rain rate via vehicle imaging radar

1. A method comprising:

receiving, at a computing device, radar data from a radar unit coupled to a vehicle, wherein the radar data represents an environment of the vehicle;

based on the radar data, determining one or more two-dimensional (2D) radar images having pixels that indicate backscatter power;

performing a comparison between power levels of the pixels in the one or more 2D radar images and power levels indicated by a rain rate model;

estimating, by the computing device, a rain rate for the environment based on the comparison; and

controlling the vehicle based on the rain rate.

2. The method of claim 1 , further comprising:

computing backscatter power based on the radar data;

determining a time-average backscatter power based on the computed backscatter power; and

determining the one or more 2D radar images based on the time-average backscatter power.

3. The method of claim 2 , wherein performing the comparison between power levels of the pixels in the one or more 2D radar images and power levels indicated by the rain rate model comprises:

performing a comparison between the time-average backscatter power and backscatter power levels represented by the rain rate model; and

estimating the rain rate for the environment based on the comparison.

4. The method of claim 1 , wherein determining the one or more 2D radar images having pixels that indicate backscatter power comprises:

determining range-Doppler images having pixels that indicate backscatter power.

5. The method of claim 1 , wherein determining the one or more 2D radar images having pixels that indicate backscatter power comprises:

determining range-azimuth spatial images that indicate backscatter power.

6. The method of claim 1 , further comprising:

determining whether the rain rate model requires calibration; and

based on determining that the rain rate model requires calibration, performing a calibration process prior to estimating the rain rate for the environment.

7. The method of claim 1 , further comprising:

based on the rain rate, triggering a sensor cleaning process for one or more sensors.

8. The method of claim 1 , further comprising:

determining that the rain rate for the environment is above a threshold rain rate; and

wherein controlling the vehicle based on the rain rate comprises:

based on determining that the rain rate is above the threshold rain rate, controlling the vehicle according to an increased following distance relative to other vehicles in the environment.

9. The method of claim 1 , further comprising:

determining a current location of the vehicle; and

providing the rain rate and an indication of the current location of the vehicle to one or more remote computing devices.

10. The method of claim 1 , further comprising:

receiving, from a second vehicle, a given rain rate and an indication of a current location of the second vehicle, wherein the given rain rate corresponding to an environment of the second vehicle;

determining that the given rain rate exceeds a threshold rain rate; and

adjusting a route of the vehicle to avoid the current location of the second vehicle.

11. The method of claim 1 , wherein the rain rate model is an empirical model fit against meteorology truth data.

12. The method of claim 1 , further comprising:

determining, based on the estimated rain rate, a max range value for the radar; and

reducing a speed of the vehicle based on the max range value determined for the radar.

13. The method of claim 1 , further comprising:

providing the estimated rain rate to a remote computing system, wherein the remote computing system is configured to update map data to convey the estimated rain rate for an area corresponding to a location of the vehicle.

14. A system comprising:

a vehicle having a radar unit;

a computing device configured to:

receive radar data from the radar unit, wherein the radar data represents an environment of the vehicle;

based on the radar data, determine one or more two-dimensional (2D) radar images having pixels that indicate backscatter power;

perform a comparison between power levels of the pixels in the one or more 2D radar images and power levels indicated by a rain rate model;

estimate a rain rate for the environment based on the comparison; and

control the vehicle based on the rain rate.

15. The system of claim 14 , wherein the computing device is further configured to:

compute backscatter power based on the radar data;

determine a time-average backscatter power based on the computed backscatter power; and

determine the one or more 2D radar images radar representation based on the time-average backscatter power.

16. The system of claim 15 , wherein the computing device is further configured to:

perform a comparison between the time-average backscatter power and backscatter power levels represented by the rain rate model; and

estimate the rain rate for the environment based on the comparison.

17. The system of claim 14 , wherein the computing device is further configured to:

determine range-Doppler images having pixels that indicate backscatter power.

18. The system of claim 14 , wherein the computing device is further configured to:

determine range-azimuth spatial images that indicate backscatter power.

19. The system of claim 14 , wherein the computing device is further configured to:

adjust parameters of one or more vehicle systems based on the rain rate.

20. A non-transitory computer readable medium configured to store instructions, that when executed by a computing device, causes the computing device to perform operations comprising:

receiving radar data from a radar unit coupled to a vehicle, wherein the radar data represents an environment of the vehicle;

based on the radar data, determining one or more two-dimensional (2D) radar images having pixels that indicate backscatter power;

performing a comparison between power levels of the pixels in the one or more 2D radar images and power levels indicated by a rain rate model;

estimating a rain rate for the environment based on the comparison; and

controlling the vehicle based on the rain rate.