Highness of Buildings ... ?

Hello, I have the following question (sorry my english is not the best)

I want to find out the height of a building that was captured and imported.

To give an exemple:

I take a screenshot of a house (from google earth), and import it in sketchup. To create a 3D-view of the building, I need the height of the building.

How do I get it?

Hi Conkin,

Post a picture of exactly what you are talking about

and also add some notes explaining your requirements.

Mike

Oh sorry, I just realised that I used a totally wrong term, I meant height and not highness. I was just a bit... confused :D ... Im sorry. I would appreaciate if someone could edit the name of the thread. Thats current name is a bit misleading

Okay, concernig my problem, I want to find out the height of a builidng,

I will give you an example:

http://img134.imageshack.us/my.php?image=unbenannt2qh.jpg [dead link]

To create a modell of for example, that house, I need the height of the building, but I have no idea, how to find it out. Do you understand what I'm talking about :D?

If you know the location (i.e. the City) the building is in and the date or general time of year the photograph was taken, you can use the Shadows in SketchUp to help determine the height. Model the footprint of the building, set up the appropriate time, date, and location in the Shadows box, and then extrude the footprint up until SketchUp's shadows match the shadows from the aerial photograph. It might not be 100% accurate, but it will be close. There is a pretty good tutorial of this at the SketchUp website called Model from a Photo. Here's the link:

http://www.sketchup.com/index.php?title=Download+Video+Tutorials [dead link]

If you know the location (i.e. the City) the building is in and the date or general time of year the photograph was taken, you can use the Shadows in SketchUp to help determine the height. Model the footprint of the building, set up the appropriate time, date, and location in the Shadows box, and then extrude the footprint up until SketchUp's shadows match the shadows from the aerial photograph. It might not be 100% accurate, but it will be close. There is a pretty good tutorial of this at the SketchUp website called "Using Pictures for Context". Here's the link:

http://www.sketchup.com/index.php?id=178&cat=13 [dead link]

@Robert

Activating your link leads me to www.sketchup.com

I would be very pleased, if you could describe how to come to that turotialsite

To manually get to the right video, hover your mouse over the Training button at the top of this webpage. Select Video Tutorials. Go to SketchUp 4 video tutorials>Adding Color and Texture. The above video is on that list.

This was a fun challenge. I don't think the shadows of the building are going to help, because all you can tell from the picture is that it's from this year. I took a different approach, I figured out where the picture is of (Dorotheenstrasse in Berlin), and then took a a while to figure out which building it might be. The closest buildings I can find are Maritim proArte and Fraktionsbufos der SPD (or something like that).

Going back on my shadow argument, if you can find out how tall the SPD build is you could calculate the mystery building's height from the size of the two shadows, regardless of when the picture was taken. It seems to be about 1.25 times the height of the SPD building.

You won't know all of the parameters for a Google image, but..

If you have a single large scale (e.g. 1:6,000) air photo on which are shown tall objects (e.g. smoke stacks, tall buildings, or very tall trees), you may be able to estimate their height using the displacement of the objects. However, the principal point and the nadir of the photo must be at the same point (that is, the air photo is perfectly vertical). You must also know the flight altitude above the base of the object. If you know the scale of the photo and the camera's focal length, you can calculate the flying height by multiplying the RF denominator (e.g. 6,000) by the camera's focal length: H = (Rfd)(f). You must be able to assume that the land surface is relatively flat, or be able to calculate the actual height of the camera above your object. Otherwise, if the elevation is variable, the scale of the object may be different from objects at the principal point. You must also be able to see clearly both the top and base of the object, and the degree of displacement (i.e. how much of the sides of the object you can see) must be great enough to be accurately measured with available tools. The greatest displacement will be seen with tall objects that are farthest from the principal point. If you have all of this information, you can calculate the height of the object using the following equation:

h = (d/r)(H)

where d = length of the displaced object from base to top

r = radial distance from the nadir to the top of the object

H = aircraft flying height above the base of the object

Wouldn't it be easiest to either find an elevation shot of the same building and use that to do the estimate, or even better, search the web for data on the building where maybe it will give the history, size, etc...

Just my .02.

Good luck!

That was my approach. Unfortunately it doesn't seem to be that famous a building, but the one next door should be. I couldn't find data online about the height of the SPD building, but it's probably written up somewhere.

If you can find the flying height for an image, it is actually quite easy to measure the other two parameters (vertical displacement and the distance to the principal point) given the measuring tools you have available in the digital programs like Google Earth.

For example if you know that an entire city was flown at 5000 feet, all you have to do is three steps:

1) find the principal point (the place in the image where buildings don't appear to "lean")

2) measure from the principal point to your object of interest

3) measure the vertial displacement ("lean") of your object from the base to the top

Then just plug these measurements into the equation and you have a decent height estimate.

This can be very quick, though not super accurate.

ALTERNATIVE:

A lot of cities are doing LIDAR flights now--where laser beams from air planes take billions of measuring points (including roof tops, trees, as well as the ground surface).

If you can get the raw LIDAR data from your citie's GIS department you will be able to get quite accurate measurements. I think I've seen a thread on how to import these LIDAR "point clouds" into sketchup.

VisualizeIT, I meant to post this a few days ago, but your formula intrigues me a lot. In your first post you say "r = radial distance from the nadir to the top of the object".

When you say "radial distance", do you mean the distance along the face of the earth or the radians the arc would describe between the principal point and the object?

Ron

the distance along the face of the earth....radial distance because it can be measured from the center (principal point).