On Fri, Oct 2, 2009 at 5:18 AM, Austin Jensen
<
address@hidden> wrote:
> Todd,
>
> We have analyzed the errors in the altitude estimation, the yaw and position
> (assuming roll and pitch were good). We found that after correcting for yaw
> error, the orthorectification error decreased to 5-20m. After correcting for
> position, the error decreased to below 5m. The altitude correction made no
> significant improvement. Since it is a more difficult problem, we haven't
> looked at roll and pitch yet, but we are working at it. Since we are using
> an IMU, we expect that our biggest contributor to this error will be GPS. If
> there are problems with roll and pitch, it will probably be a bias from the
> sensor or a misalignment between the camera and the IMU. We will see though.
>
> Austin
>
> ------------------------------------------------------------------
> Austin Jensen, Research Engineer
> Utah Water Research Laboratory (UWRL)
> Utah State University, 8200 Old Main Hill
> Logan, UT, 84322-8200, USA
> E:
address@hidden
> T: (435)797-3315
>
>
> On Thu, Oct 1, 2009 at 10:10 AM, Todd Sandercock <
address@hidden>
> wrote:
>>
>> Hi Austin and all
>> I am guessing that most of the error came from roll and pitch in your
>> study. Do you think this could be rectified by a stabilised camera on board
>> that ideally always faces directly down?
>> Of course there is always the error in yaw but that can be solved in a few
>> different ways
>> Todd
>> ________________________________
>> From: Austin Jensen <
address@hidden>
>> To:
address@hidden
>> Sent: Thursday, 1 October, 2009 3:33:22 AM
>> Subject: Re: [Paparazzi-devel] georeferencing video stream?
>>
>> Chris,
>>
>> Sounds like your on the right track. The biggest problem you will face
>> will be the accuracy of your orthorectification based on the sensors of the
>> aircraft (especially the IR sensors). We did a study on it and found that
>> the orthorectification error can vary from 5 to 40m depending on your
>> altitude. And that was using an IMU. Here is an example ..
>>
>>
http://www.engr.usu.edu/wiki/index.php/Image:OSAMBeforeMan.PNG
>>
>> We are working on ways to improve this by calibrating the aircraft sensors
>> in flight.
>>
>> I suspect that the method used to georeference the images in the
>> presentation you mentioned might use the aircraft sensors to help
>> georeference, but its probably more based on the features in the images. I
>> know of one open source project that stitches images based on features.
>>
>>
http://jimatis.sourceforge.net/
>>
>> A different propriatory software called ensomosaic does a very good job at
>> georeferencing the images using position, orientation and position.
>>
>>
http://www.ensomosaic.com/
>>
>> Austin
>>
>> ------------------------------------------------------------------
>> Austin Jensen, Research Engineer
>> Utah Water Research Laboratory (UWRL)
>> Utah State University, 8200 Old Main Hill
>> Logan, UT, 84322-8200, USA
>> E:
address@hidden
>> T: (435)797-3315
>>
>>
>> On Wed, Sep 30, 2009 at 1:14 AM, Todd Sandercock
>> <
address@hidden> wrote:
>>>
>>> I am working on the same ideas as you.
>>> Paparazzi is extremely suitable for this because it is soooooo easy get
>>> your hands on any data that you want by using the Ivy bus.
>>> Skipping the image processing part and using location from paparazzi
>>> seems to be a more feasible initial solution though. That is if position on
>>> the ground is something important to you....
>>> Finding a GIS client suitable for the job i have found extremely
>>> difficult. Looking around in the image processing area of the OSAM wiki is
>>> one successful implementation though.
>>> Todd
>>> ________________________________
>>> From: Chris Gough <
address@hidden>
>>> To:
address@hidden
>>> Sent: Wednesday, 30 September, 2009 9:11:57 AM
>>> Subject: [Paparazzi-devel] georeferencing video stream?
>>>
>>> Sorry if this is be a bit off topic, but...
>>>
>>> The Thales SpyArrow presentation linked to from the wiki home page
>>> (
http://newton.ee.auth.gr/aerial_space/docs/CS_4.pdf) refers to a
>>> system where the live video stream is georeferenced, and shows images
>>> of what appears to be a stitched image. I'm interested in how to do
>>> this, and was hoping somebody might give me some hints.
>>>
>>> I had imagined post-processing (on the ground) combination of video
>>> and telemetry:
>>> 1. Convert the video stream into a "timestamped sequence of images"
>>> as they arrive,
>>> using the native features of a video capture card and operating
>>> system.
>>> 2. Interpolate the telemetry stream to estimate {lat, long, altitude,
>>> pitch, roll, yaw}
>>> at the exact time of each image.
>>> 3. Orthorectify each image and load them into a temp GIS raster layer
>>> in a database
>>> 4. Use elevation model and some geometry to infer the locaction of
>>> some points in
>>> the streatched image.
>>> [4b. use fancy pattern recognition and/or umpa-lumpas to identify
>>> points...]
>>> 5. Process the images (stitch, filter, etc) and post fixed
>>> rectangular tiles to another
>>> GIS layer.
>>> 6. Combine tiles (perhaps allong with other spatial data) in a GIS
>>> client to produce
>>> images/maps as required (periodically refreshed).
>>>
>>> am I on the right track? Is there a working open source solution already?
>>>
>>> Chris Gough
>>>
>>>
>>> _______________________________________________
>>> Paparazzi-devel mailing list
>>>
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>>>
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>>
>>
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