Estimating the height of an object.
If you do not know the height of an object you are planning to model, there are some easy to use techniques that will enable you to make an educated guess.
This explanation uses a square building as an example, the same technique can be used to measure any tall object or building.
Count repeated units
Often buildings are constructed with bricks, blocks or other modular materials so its possible to measure the height of a single unit, count the total number of units on the face of the building, and multiply to get an approximate overall height.
This method also works for entire building levels. If you can measure a single level on the face of your building, you can multiply by the total number of levels to arrive at an approximate overall measurement.
You can also measure the length of something by striding out along the length and the measuring your stride. Multiply the length of the stride my the number of strides and you have the length.
Take a picture with an item or object of a known height
When you are taking a picture of the building you plan to model, include something, or someone, in the photo whose height you know.
a. be sure to position your "known quantity" as close to the building as possible for accuracy
b. take the photo from as far away as possible to minimize vertical distortion
Use simple trigonometry
With a few simple measurements it is possible to estimate heights with some accuracy. Take a look at the image below. All you need to know is:
1. your distance from the building. This an be accurately measured or can be
roughly paced out.
2. your eye height.
3. the angle between the ground and the top of the building. Again either an estimated guess or accurate will work, but a protractor is best used.
There are mobile phone apps that will allow you to add a spirit level to your phone, which will give you the correct and accurate angle.
Use this formula to calculate the height of the building:
Height = ( tan(angle) x distance ) + eye height
Example: Given a building distance of 25 meters, an angle of 37 degrees, and an eye height of 1.75 meters, the formula would be:
Height = tan(37) x 25m + 1.75m
= 0.75355 x 25m + 1.75m
Note: Use the tan button on your calculator to calculate the tangent of an angle. Again, phone apps are available with calculators that have a tan key.