Method and apparatus for determining the speed of a vehicle travelling along a road by processing images of the road

A non-transitory computer-readable medium comprising instructions that, when executed by a processor, cause the processor to execute a method of determining a speed of a vehicle travelling along a road by processing pairs of images of the road that have been captured by a camera mounted on the vehicle, each of the pairs of images having a common image coordinate system and including a first image of the road and a second image of the road, the first image having been captured at a first time instant, the second image having been captured at a second time instant that is a predefined time period after the first time instant, and the first image and the second image including respective road marker images of a road marker on the road, the method including processing each of the pairs of images by:

• determining a location, in the image coordinate system, of the road marker image in the first image by:
• generating an LL sub-band image of an Mth level of an (M+1)-level discrete wavelet transform (DWT) decomposition of the first image by iteratively low-pass filtering and down-sampling the first image M times, wherein M is an integer equal to or greater than one;
• generating a sub-band image of an (M+1)th level of the (M+1)-level DWT decomposition of the first image by high-pass filtering the LL sub-band image of the Mth level, and down-sampling a result of the high-pass filtering;
• generating boundary data indicative of a boundary of the road marker image of the first image, by determining a boundary of a region of pixels of the sub-band image of the (M+1) th level, the region of pixels being surrounded by pixels of different pixel values to the pixel values of the pixels in the region;
• and
• determining the location of the road marker image in the first image by upscaling the boundary data of the region of pixels of the sub-band image of the (M+1)th level by a factor of 2M+1;
• predicting a location, in the image coordinate system, of an image of the road marker in the second image based on the determined location of the road marker image, an estimate of the speed of the vehicle, and the predefined time period;
• detecting an image of the road marker in a portion of the second image at the predicted location;
• estimating a distance by which the vehicle has travelled along the road during the predefined time period based on the determined location of the road marker in the first image, and a location of the detected image of the road marker in the portion of the second image;
• and
• calculating the speed of the vehicle based on the estimated distance and the predefined time period.

An apparatus for determining a speed of a vehicle travelling along a road by processing pairs of images of the road that have been captured by a camera mounted on the vehicle, each of the pairs of images having a common image coordinate system and including a first image of the road and a second image of the road, the first image having been captured at a first time instant, the second image having been captured at a second time instant that is a predefined time period after the first time instant, and the first image and the second image including respective road marker images of a road marker on the road, the apparatus comprising:

• memory hardware configured to store instructions;
• and
• processor hardware configured to execute the instructions stored by the memory hardware, wherein the instructions include processing each of the pairs of images by:
• determining a location, in the image coordinate system, of the road marker image in the first image by:
• generating an LL sub-band image of an Mth level of an (M+1)-level discrete wavelet transform (DWT) decomposition of the first image by iteratively low-pass filtering and down-sampling the first image M times, wherein M is an integer equal to or greater than one;
• generating a sub-band image of an (M+1)th level of the (M+1)-level DWT decomposition of the first image by high-pass filtering the LL sub-band image of the Mth level, and down-sampling a result of the high-pass filtering;
• generating boundary data indicative of a boundary of the road marker image of the first image, by determining a boundary of a region of pixels of the sub-band image of the (M+1)th level, the region of pixels being surrounded by pixels of different pixel values to the pixel values of the pixels in the region;
• and
• determining the location of the road marker image in the first image by upscaling the boundary data of the region of pixels of the sub-band image of the (M+1) th level by a factor of 2M+1;
• predicting a location, in the image coordinate system, of an image of the road marker in the second image based on the determined location of the road marker image, an estimate of the speed of the vehicle, and the predefined time period;
• detecting an image of the road marker in a portion of the second image at the predicted location;
• estimating a distance by which the vehicle has travelled along the road during the predefined time period based on the determined location of the road marker in the first image, and a location of the detected image of the road marker in the portion of the second image;
• and
• calculating the speed of the vehicle based on the estimated distance and the predefined time period.