[Talk-GB] Measuring building height

Warin 61sundowner at gmail.com
Wed Mar 20 23:08:22 UTC 2019


On 21/03/19 08:39, Devonshire wrote:
> This stuff is hilarious. Standing outside people's homes taking photos 
> of their cars and house isn't going to end very well.

I'd simply visually estimate the hight of a home - no photo required.

For a multi story building visual estimations start to get uncertain. 
Here I'd be using other methods.


>
> Is it maybe possible to get building heights from lidar data?

Too much clutter (multiple reflections) in a city for that to work well 
I'd think.
>
> Kevin
>
> On Tue, Mar 19, 2019, at 11:17 PM, Warin wrote:
>> On 20/03/19 07:51, Neil Matthews wrote:
>> >
>> > So, I just tried this and I think it has a reasonable chance of giving
>> > a reasonable result.
>> >
>> > Take a photo of a car outside the building. Measure number of pixels
>> > for the car and number of pixels for the building and the height can
>> > be approximated by:
>> >
>> >     building_pixels / car_pixels * car_height_in_m
>> >
>> > I reckon an average of 1.5m might be reasonable for the car height --
>> > otherwise use something more detailed:
>> > https://www.automobiledimension.com/ford-car-dimensions.html
>> >
>> >
>> > Obviously, the further the car is from the building the less accurate
>> > the measurement will be.
>> >
>>
>> The further the camera/photo is from the building the better too. Less
>> camera distortion.
>> >
>> >
>> > Cheers,
>> >
>> > Neil
>> >
>> >
>> > On 19/03/2019 16:23, Tony Shield wrote:
>> >>
>> >> Hi
>> >>
>> >> Been figuring out how to do this for a while - my solution-
>> >>
>> >> rule - I used 30cm (aka 1 foot), calculator, known length of arm - in
>> >> my case .6m, OSM map to measure distance from target.
>> >>
>> >> With hand holding rule vertically measure the target height against
>> >> the rule for rule height, this is the key measurement, note the
>> >> measurement point. From the map measure the distance from the
>> >> measuring point to the target
>> >>
>> >> With this information and using proportions (which is what a tangent
>> >> is) -
>> >>
>> >> target height = (rule height in metres * distance from measuring
>> >> point to target) / length of arm in metres.
>> >>
>> >> Using this technique I have this morning measured known height of of
>> >> a local landmark, and the unknown height of a building. The known
>> >> height of 50m measured 8cm at a range of 375m. The unknown height of
>> >> the building with 5 floors was calculated to be 20.7 metres which
>> >> would on the face of it be realistic (from 3cm and 414m). (Botany Bay
>> >> mill in Chorley).
>> >>
>> >> TonyS999
>> >>
>> >>
>>
>>
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>
>
>
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