User:PieSchie\Mapping

Enhanced Mapping

As I have no real access to the railway-stations rail-yard. It is very difficult to estimate locations of signals and switches. Therefore I took some geometrical help. As on some Digital cameras the focal length is well known and then sensor-size (the size of the projected image in the camera( is also well known following calculations are possible:

Calculating Distances with known Original-Size

I took the following Input-Values:

• Original Size of Object (Railway-gauge = 1435mm) om
• Horizontal Sensor-Size (22,2mm) = sm
• Real Focal Length of a image (eg. 108mm) (see below) = f
• Image-Size in pixel (3456px) = ip
• Image-Size of the object in Pixel (90px) = op

With these information a simple math-solution is possible to create in every spreadsheet-application:

• Object-Size on the sensor osm = sm * op / ip (22,2mm*92px/3456px)
• R = osm / om
• distance d in mm = f * R

Now anyone can say that the size of the sensor chip and this pixel-size of the object is very difficult to get. I agree with that, but getting a Pixel-Size of 88 to 92 Pixels the Distance of the example above varies between 223 and 233 meters.

Some Point-And-Shoot Cameras with an intergrated Photographic lens have a focal length given that equals the 35mm-format. For the real distance the real focal length is needed:

• real Focal Length = 35mm-format focal length * sensor-width in mm / 36mm

Calculating Distances from size-distance-change

Input-Values

• Object-Size in pixel from Distance 1 (s1) = l1
• Object-Size in pixel from Distance 2 (s2) = l2
• let there be s1 > s2 and so l1 < l2
• Changed distance in m (as precise as possible) s1-s2 = ds

With these information a simple math-solution is possible to create in every spreadsheet-application:

• size-difference in percent p = s2/s1 - 1
• s1 = ds / p
• s2 = ds+s1