[ros-users] Stereo, distance measurement

[Daniel Maturana]

It is in the image itself, that is the disparity at position x,y is at
image(x,y). You could also use the Z value of the points in the point
cloud.
Daniel

On Wed, Feb 2, 2011 at 8:28 PM, Homer Manalo
<homer.manalo at roboteknik.com> wrote:
> Anyone knows how to get d(disparity) from the DisparityImage.msg?
>
> On Wed, Feb 2, 2011 at 5:33 PM, Homer Manalo <homer.manalo at roboteknik.com>
> wrote:
>>
>> According to the documentation of DisparityImage.msg:
>>
>> http://www.ros.org/doc/api/stereo_msgs/html/msg/DisparityImage.html
>>
>> depth can be calculated by Z=fT/d, so far I can get the minimum distance:
>>
>>         distance = data.f*data.T/data.max_disparity
>>     print "Minimum distance:", distance, "meters"
>>
>>         Minimum distance: 0.430558934726 meters
>>
>> How do you get d(disparity) here?
>>
>> On Wed, Feb 2, 2011 at 11:37 AM, Homer Manalo
>> <homer.manalo at roboteknik.com> wrote:
>>>
>>> Ok, so I need to manually extract this? Or is there a command to show
>>> this up? Which one is it contained:
>>>
>>> [sensor_msgs/PointCloud2]:
>>> Header header
>>>   uint32 seq
>>>   time stamp
>>>   string frame_id
>>> uint32 height
>>> uint32 width
>>> sensor_msgs/PointField[] fields
>>>   uint8 INT8=1
>>>   uint8 UINT8=2
>>>   uint8 INT16=3
>>>   uint8 UINT16=4
>>>   uint8 INT32=5
>>>   uint8 UINT32=6
>>>   uint8 FLOAT32=7
>>>   uint8 FLOAT64=8
>>>   string name
>>>   uint32 offset
>>>   uint8 datatype
>>>   uint32 count
>>> bool is_bigendian
>>> uint32 point_step
>>> uint32 row_step
>>> uint8[] data
>>> bool is_dense
>>>
>>> [stereo_msgs/DisparityImage]:
>>> Header header
>>>   uint32 seq
>>>   time stamp
>>>   string frame_id
>>> sensor_msgs/Image image
>>>   Header header
>>>     uint32 seq
>>>     time stamp
>>>     string frame_id
>>>   uint32 height
>>>   uint32 width
>>>   string encoding
>>>   uint8 is_bigendian
>>>   uint32 step
>>>   uint8[] data
>>> float32 f
>>> float32 T
>>> sensor_msgs/RegionOfInterest valid_window
>>>   uint32 x_offset
>>>   uint32 y_offset
>>>   uint32 height
>>>   uint32 width
>>> float32 min_disparity
>>> float32 max_disparity
>>> float32 delta_d
>>>
>>>
>>> Thanks,
>>> Homer
>>>
>>> On Wed, Feb 2, 2011 at 11:17 AM, Daniel Maturana <dimatura at gmail.com>
>>> wrote:
>>>>
>>>> Both the the disparity and the points2 messages have the information
>>>> you need. Note that your camera should be calibrated.
>>>> best,
>>>> Daniel
>>>>
>>>> On Tue, Feb 1, 2011 at 8:13 PM, Homer Manalo
>>>> <homer.manalo at roboteknik.com> wrote:
>>>> > I've actually used it for viewing disparity and rectifying images.
>>>> > What
>>>> > topic exactly are you referring to?
>>>> >
>>>> > Homer
>>>> >
>>>> > On Tue, Feb 1, 2011 at 11:43 PM, Daniel Maturana <dimatura at gmail.com>
>>>> > wrote:
>>>> >>
>>>> >> Try http://www.ros.org/wiki/stereo_image_proc.
>>>> >> Daniel
>>>> >>
>>>> >> On Tue, Feb 1, 2011 at 4:13 AM, Homer Manalo
>>>> >> <homer.manalo at roboteknik.com> wrote:
>>>> >> > Are there packages that convert stereo data into real world
>>>> >> > measurements
>>>> >> > -
>>>> >> > how far an object is from camera?
>>>> >> >
>>>> >> > Thanks,
>>>> >> > Homer
>>>> >> >
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>>>
>>
>
>
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