App to calculate what is in view?

edited June 2015 in Technique
I was wondering if somebody knows an app to see 'what's in view'? I have done some searches over the net, but what I did found was not exactly what I need or I just don't know the right words to search on.
I am an RC KAPper without FPV. So if my apsc cam with 24mm is 70 meters up, looking strait down, I want to know how many meters will be in view (on ground level). I can calculate it of course, but with different heigths and camera angles (!) an app would be more convenient. Ideally it would compose a simple draw with an upside down triangle so you can find out if the (higher) object would fit in the shot.

Any idea?



  • edited June 2015
    I don't know about an easy app, but if you are willing to tweak an XML file you can get Google Earth to show you any view. Save the text below in a file (say test.kml) and open it in Google Earth.

    Not very user friendly, but fun to play with!

    Range is the altitude of the camera, horizFov is the horizontal field of view (must match you camera/lens)

    NOTE: I did not manage to quote the xml text properly in this post, so I placed the example here:
  • Not an application because it's too old, but an abacus to be use on the field or with a detailed map.

    It needs to know some distances, the wind direction, the line angles, the pan and tilt of the camera, and the field angles (vertically and horizontally) of the lens.
    When the problem looks complex, the abacus is in fact simple. The step by step procedure is much longer to read than to apply. It takes any scale you decide, meter or feet, and the angles are already drawn. It is instinctive and visual.
    It doesn't need to be accurate to be helpful.

    Let's try itAbacus targetting

    It is not exactly the answer to the quesqtion of this post, but it can be used for it.
    In the book which I publishes many years ago there were drawings of the field shot by the camera depending on distance and tilt, but I have not publisted it yet on the web. May be, I should.
  • edited June 2015
    Hello Hans and Christian,

    Thank you both for your suggestions! I was just playing with the method of Hans, so let's concentrate on that in this reply and later on I will post my comment on Christian's solution. The KML file solution is actually a very convenient one because if I want to go KAPping I always have some object in mind. So it is always good to do some homework first and that is what I usually do. A few weeks ago I made some pictures of the Seatower (Hans you will probably know this tower) in my hometown. With my new 24 mm (ef-s) lens I had no idea how high the camera should hang. With Hans' solution I figured out that if I want to capture (looking strait down) the tower without any need to crop, I should hang the camera at around 80 meters. These are the parameters I used in the KML example file of Hans:


    So that's quite high and just under the 100 meter restriction in Holland for kite flying. Assuming that the camera is hanging only 20 meters under the kite. Just 20 meters... eh... oops ;-). So I think I need to use my more expensive 10-22mm, which is acutally my wife's lens :-)

    So if somebody would fit such in an app (including a fov calculator), it will be even better than my suggestion with the upside down triangle, as you can show the result directly on a map (and maybe even in 3D!). Honestly now I think there is not such an app because (I think) it is not very usefull for other things than KAPping (or BAP), as most drones for example are using FPV. I know a little PHP, so maybe I could build something as a web-based app.

    Thanks Hans for this good solution!
  • edited June 2015
    Here is a thread from 2008 showing a practical tool you can carry in your pocket. You can set your rig angle and use the same angle on the device, holding it up to the sky, with the origin of the triangle at the rig position. The lines showing the lens angle will show whether your subject will fall within the frame. So the device is preset with the lens angle, and held at the camera angle. Of course it doesn't do anything for judging the relevant downwind distance .
  • edited June 2015
    Hello Christian,

    After putting my little daugther in bed I have found some time to dig into my memory and see if I remember all the things I have learned during maths. Fortunately I do remember at least the Pythagorean theorem which I needed to calculate the distances in your well thought sheet. I get it! :-) It is amazing that you can find out line length, tilt and pan angle with 'just a piece of paper'. Good job!

    Although is it not 100% what I need, it is very usefull and you will not need internet nor any device. However I think I have to practice a few times to calculate these parameters in your suggested 3 minutes (but that might be my shortcoming) ;-)

    Thanks for your 'trick'. I have printed it and will do some tests next time in the field.
  • edited June 2015
    Hi Simon,

    Aha, a protractor! That's a very simple and good solution. Of course you will still need to know if your rig is at the same distance as you are to the subject (or in other words, at the same line of the subject), but my goal was to find a way to see if the subject fits in the picture and that can be done this way. Bravo!

    I have one at home, so will definately try this next KAP session.


  • Hi, Bill Blake has done quite recently a blog page that was for an equivalent request :
    SMAC from Italy

  • Here's my take on the app you're looking for. The question I wanted to answer is "what percentage of the camera's field of view is taken up by an object of known size"? Usually I know what I want to photo, but don't know the best elevation or what cropping will be around the object. Starting with the object also makes the math possible.

    Python code at,
    along with pre-calculated graphical and HTML text tables for common KAP cameras.

    Github tries to protect the viewer from evil html files, so you may have to download them & load in your browser.
    Or you can paste an HTML page URL into, like the table at

    Sample for a Ricoh GR camera: image

  • thanks Myles, I have a RICOH GR so your charts are immediately of possible help
    SMAC from Italy
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