Re: [Talk-GB] Measuring building height

2019-03-20 Thread Warin 

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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Re: [Talk-GB] Measuring building height

2019-03-20 Thread Devonshire 
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?

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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Re: [Talk-GB] Measuring building height

2019-03-19 Thread Warin 

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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Re: [Talk-GB] Measuring building height

2019-03-19 Thread Neil Matthews 
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.


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
>
> On 19/03/2019 09:30, Brian Prangle wrote:
>> There are also theodolite apps for smartphones
>>
>> On Tue, 19 Mar 2019, 00:17 Rob Nickerson, > > wrote:
>>
>> For building heights why not try using a laser measure? Those
>> with a Pythagoras Measurement mode should automate the
>> calculations for you.
>>
>> Price has fallen a lot over the years. Seems like even a basic
>> £30 device is sufficient.
>>
>> Best regards,
>> Rob
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Re: [Talk-GB] Measuring building height

2019-03-19 Thread Tony Shield 

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

On 19/03/2019 09:30, Brian Prangle wrote:

There are also theodolite apps for smartphones

On Tue, 19 Mar 2019, 00:17 Rob Nickerson, > wrote:


For building heights why not try using a laser measure? Those with
a Pythagoras Measurement mode should automate the calculations for
you.

Price has fallen a lot over the years. Seems like even a basic £30
device is sufficient.

Best regards,
Rob
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Re: [Talk-GB] Measuring building height

2019-03-19 Thread Brian Prangle 
There are also theodolite apps for smartphones

On Tue, 19 Mar 2019, 00:17 Rob Nickerson,  wrote:

> For building heights why not try using a laser measure? Those with a
> Pythagoras Measurement mode should automate the calculations for you.
>
> Price has fallen a lot over the years. Seems like even a basic £30 device
> is sufficient.
>
> Best regards,
> Rob
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