Simple measurements and calculations on digital aerial photographs

Géza Király, PhD

The aim of this exercise is helping to understand the general principals of central projection, and to be capable to make measurements on aerial photographs and photo-pairs.
A (secondary) digital metric aerial image-pair are published, but it is important to note, that all the measurements can be done by traditional devices (such as ruler or micrometer) on the contact copies.
One software is necessary for the exercise, which can handle the ER Mapper compressed wavelet (*.ecw) format, and can measure pixel-coordinates on it. Suggested software are:

Things should be submitted

The followings should be included:

  • General description of the image-pair (film-type, estimated scale and/or ground resolution, camera type and serial number of optic, displayed area, time and season of the image).
  • Scanning resolution: res’ (mm/pixel) – for both images.
  • Scale, scale-number – and the screenshots of the applied distances (in DigiTerra and Google Earth) – for both images.
  • Ground resolution: res (m/pixel) – for both images.
  • Flying height: h0 (m) – for both images.
  • Ground and image base distance – The mean of the values determined on both photos.
  • height determination of 1 tree based on 1 image:
    – Leaning: Δr’ (mm); nadir distance: r’ (mm); screenshot of the measured object; height: Δh (m);
  • height determination of 2 trees based on 2 images – one conifer and one deciduous are suggested, and one can be identical with the above single-image determination:
    – Parallaxes: Δp (mm); screenshots of the objects from both images; heights: Δh (m).

The exercise should be submitted in *.pdf format, or emailed to the following address:

Deadline: 2 weeks from the issue.

Sopron, 6th of November, 2013.

Dr. Király, Géza
associate professor