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<div class="moz-cite-prefix">On 21/03/19 08:39, Devonshire wrote:<br>
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<div>This stuff is hilarious. Standing outside people's homes
taking photos of their cars and house isn't going to end very
well.<br>
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<br>
I'd simply visually estimate the hight of a home - no photo
required. <br>
<br>
For a multi story building visual estimations start to get
uncertain. Here I'd be using other methods. <br>
<br>
<br>
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<div> Is it maybe possible to get building heights from lidar
data?<br>
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<br>
Too much clutter (multiple reflections) in a city for that to work
well I'd think. <br>
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<div>Kevin</div>
<div><br>
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<div>On Tue, Mar 19, 2019, at 11:17 PM, Warin wrote:<br>
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<div>On 20/03/19 07:51, Neil Matthews wrote:<br>
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<div>><br>
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<div>> So, I just tried this and I think it has a reasonable
chance of giving <br>
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<div>> a reasonable result.<br>
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<div>><br>
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<div>> Take a photo of a car outside the building. Measure
number of pixels <br>
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<div>> for the car and number of pixels for the building and
the height can <br>
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<div>> be approximated by:<br>
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<div>><br>
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<div>> building_pixels / car_pixels * car_height_in_m<br>
</div>
<div>><br>
</div>
<div>> I reckon an average of 1.5m might be reasonable for
the car height -- <br>
</div>
<div>> otherwise use something more detailed: <br>
</div>
<div>>
<a class="moz-txt-link-freetext" href="https://www.automobiledimension.com/ford-car-dimensions.html">https://www.automobiledimension.com/ford-car-dimensions.html</a><br>
</div>
<div>><br>
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<div>><br>
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<div>> Obviously, the further the car is from the building
the less accurate <br>
</div>
<div>> the measurement will be.<br>
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<div>><br>
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<div><br>
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<div>The further the camera/photo is from the building the
better too. Less <br>
</div>
<div>camera distortion.<br>
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<div>><br>
</div>
<div>><br>
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<div>> Cheers,<br>
</div>
<div>><br>
</div>
<div>> Neil<br>
</div>
<div>><br>
</div>
<div>><br>
</div>
<div>> On 19/03/2019 16:23, Tony Shield wrote:<br>
</div>
<div>>><br>
</div>
<div>>> Hi<br>
</div>
<div>>><br>
</div>
<div>>> Been figuring out how to do this for a while - my
solution-<br>
</div>
<div>>><br>
</div>
<div>>> rule - I used 30cm (aka 1 foot), calculator, known
length of arm - in <br>
</div>
<div>>> my case .6m, OSM map to measure distance from
target.<br>
</div>
<div>>><br>
</div>
<div>>> With hand holding rule vertically measure the
target height against <br>
</div>
<div>>> the rule for rule height, this is the key
measurement, note the <br>
</div>
<div>>> measurement point. From the map measure the
distance from the <br>
</div>
<div>>> measuring point to the target<br>
</div>
<div>>><br>
</div>
<div>>> With this information and using proportions (which
is what a tangent <br>
</div>
<div>>> is) -<br>
</div>
<div>>><br>
</div>
<div>>> target height = (rule height in metres * distance
from measuring <br>
</div>
<div>>> point to target) / length of arm in metres.<br>
</div>
<div>>><br>
</div>
<div>>> Using this technique I have this morning measured
known height of of <br>
</div>
<div>>> a local landmark, and the unknown height of a
building. The known <br>
</div>
<div>>> height of 50m measured 8cm at a range of 375m. The
unknown height of <br>
</div>
<div>>> the building with 5 floors was calculated to be
20.7 metres which <br>
</div>
<div>>> would on the face of it be realistic (from 3cm and
414m). (Botany Bay <br>
</div>
<div>>> mill in Chorley).<br>
</div>
<div>>><br>
</div>
<div>>> TonyS999<br>
</div>
<div>>><br>
</div>
<div>>><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>_______________________________________________<br>
</div>
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<div><br>
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