[OSM-talk] Aerial Photographs (was: People's Map)

[Eric Wolf]

Touche' - I can't believe I mixed up AGL and MSL - especially since I
live at 5400 feet MSL!

-Eric

-=--=---=----=----=---=--=-=--=---=----=---=--=-=-
Eric B. Wolf                          720-209-6818
USGS Geographer
Center of Excellence in GIScience
PhD Student
CU-Boulder - Geography




On Thu, Apr 16, 2009 at 6:23 AM, Chris Hill <chillly809 at yahoo.co.uk> wrote:
> A local man used a radio-controlled glider tp photograph our village and an
> archaeological dig a couple of miles away.  One problem with RC planes is
> that they are unstable in the air because of their short wing-span, so the
> camera points left and right wildly.  A glider has much longer wingspan and
> is more stable laterally.  The glider used has a small electric motor to get
> it into the air and worked quite well for general shots of the area but to
> use it to systematically photograph a wide area is an unthinkable difficult
> task for any usefully big area.
> The height restriction is AGL, not MSL or you could never fly slope soarers
> in the Pennines. :-)
>
> Cheers, Chris
>
> Eric Wolf wrote:
>>
>> RC airplanes aren't cheaper for two reasons:
>>
>> 1. RC airplanes (and any civilian-operated UAV) has significant flight
>> restrictions - distance and altitude. Flying at low altitude (under
>> 500 feet MSL), you end up with a higher spatial resolution but you
>> have to stitch together many more images to cover the same extent as a
>> single image taken from an aircraft flying at, say, 2000 feet MSL.
>> Selecting good shots and correcting the imagery for hundreds of images
>> ends up costing more than the difference in operating an RC plane and
>> a regular aircraft.
>>
>> 2. RC airplanes crash - often - and they aren't cheap. Sure, regular
>> airplanes are more expensive but they don't crash as often. A decent
>> RC rig will set you back $1000+ - not counting the camera.
>>
>> I used balloons and blimps to do low-altitude aerial photography in my
>> MS thesis. They are much cheaper than RC planes to operate because
>> they don't crash (as easily). But you also don't have as much control.
>> They work really well for taking low-altitude obliques for general
>> documentation processes. But for creating a basemap of  aerial
>> imagery, you need to get above the 500 ft MSL barrier put in place by
>> the FAA. To do this, you have to be in an airplane piloted by a
>> licensed pilot.
>>
>> Surprisingly, hiring a light aircraft - like the one used in this
>> study - is not really all that expensive.
>>
>> -Eric
>>
>> -=--=---=----=----=---=--=-=--=---=----=---=--=-=-
>> Eric B. Wolf                          720-209-6818
>> USGS Geographer
>> Center of Excellence in GIScience
>> PhD Student
>> CU-Boulder - Geography
>>
>>
>>
>>
>> On Wed, Apr 15, 2009 at 6:25 PM, Keith Ng <khensthoth at gmail.com> wrote:
>>
>>>
>>> Couldn't the process of obtaining aerial photographs be made much cheaper
>>> with RC planes? I am not sure if it would work but setting the RC plane
>>> on
>>> auto pilot and attaching a camera with continuous shooting mode might
>>> make
>>> the process simpler.
>>>
>>> Also refering to this link, a commentator said:"Just wanted to make it
>>> clear
>>> that we (Pict'Earth) are willing to help anyone from the DIYDrones group
>>> to
>>> get their UAV imagery processed and published in OAM, just let us know.
>>> If
>>> you can fly with a logging GPS and a digicam, our Win32 software will get
>>> you part of the way and we can help with the rest of the manual bits
>>> until
>>> we get it truly automatic."
>>>
>>>
>>> On Thu, Apr 16, 2009 at 4:06 AM, Blumpsy <blumpsy at yahoo.co.uk> wrote:
>>>
>>>>
>>>> There is an interesting paper from our dear friends over in Redmond:
>>>>
>>>> http://research.microsoft.com/apps/pubs/default.aspx?id=75312
>>>>
>>>>  From the article:
>>>> "Our mission, in contrast, involved an ordinary four seat Cessna
>>>> ($160/hour rental, including pilot), three feet of PVC pipe, a consumer
>>>> digital camera ($300), and two people: one pilot and one to operate the
>>>> camera shutter and change the batteries (Figure 2). In post-processing,
>>>> we identified 25 ground reference pairs, and used 60 photos to produce a
>>>> 208 megapixel image at a resolution of 0.15 m/pixel"
>>>>
>>>> The camera in Figure 2 looks exactly like the one I have sitting right
>>>> next to me: a Canon Power Shot A640 with 10MP.
>>>>
>>>> I found it rather entertaining to have an operator to press the trigger
>>>> and swap batteries. For this, there is surely a more elegant solution
>>>> (PSU and gphoto2)
>>>>
>>>> Anyhow, maybe one or the other finds this interesting and inspiring.
>>>>
>>>> Cheers
>>>>
>>>> Blumpsy
>>>>
>>>>
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>>
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