overlayaz

Photo visibility analysis software.

Latest version: v1.0-beta1 (2022-04-18)

  • Windows: 64-bit (build 2022-04-18)
    [sha256: 52adbd4ddd9f07a472759b1d80b0832a8a8596d6381f2c12c2cc14f4407ab11e]
  • Source code: GitHub (GNU/Linux, Windows)

Arch Linux AUR repository contains overlayaz-git package. Download and build it with your favorite AUR installer.

Tutorial:

  1. Open a picture in overlayaz (drag and drop is also supported).
  2. If necessary, rotate the image to level the horizon (quite difficult).
    Use rotation knob on the right window side or hold Ctrl button and use mouse scroll.
  3. Set latitude and longitude of the location where the photo was taken.

    You can enter the coordinates manually or use map view (with right mouse button).
    Altitude value is optional for elevation angle calibration.
  4. Set azimuth reference – use right mouse button to select position (image) and location (map).
    • Single point reference with known ratio (pixels per one degree)
    • Two point reference 
  5. Set elevation reference – you can easily reuse ratio value from azimuth reference (paste button).
  6. Switch menu to Marker tab and add as many markers as you wish (using right mouse button).

Object identification:

  1. Create a new marker using the image view (right mouse button).
    Marker path distance is the same as map grid distance set in preferences (default 100 km).
  2. Switch view to the map and follow the path from the photo location until you find something on the way.
  3. Create a new marker to the discovered object.
  4. Remove the marker created at the beginning.

Tips & tricks:

  • Store coordinates in preferences and recall them with home button.

    This is useful for dealing with multiple photos taken at the same location.
  • Use middle mouse button to get detailed information about image or map coordinates.
  • Download SRTM data (HGT files) for your neighborhood and set path in preferences to automatically examine altitude (height above sea level).
  • Make sure that lens correction is applied to the picture! Avoid wide angle lens (too much distortion).
    Personally I use the following lens: Canon EF 50mm f/1.4 USM, EF 70-300 mm f/4-5.6 EF IS II USM.
  • Keyboard shortcuts:
    Alt + 1 – switch to image view
    Alt + 2 – switch to map view
    Z – zoom image in (100%)
    X – zoom image out (fit to window)
  • Geodesic computations (incl. distance and azimuth) are performed using GeographicLib (which implements spheroid model). These algorithms provide the highest level of accuracy and produce different results than typical calculations (i.e. great-circle distances).

Example:

This (unprocessed) photo with overlayaz profile is available in example directory.

Changelog:

  • v1.0-beta1 – 2022-04-18:
    First public release