[Talk-GB] Measuring building height
maps at fortyfivekev.co.uk
Wed Mar 20 21:39:12 UTC 2019
This stuff is hilarious. Standing outside people's homes taking photos of their cars and house isn't going to end very well.
Is it maybe possible to get building heights from lidar data?
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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