Frequently Asked Questions

If you think TARAN is great, and in a surge of generosity want to pay me a beer or a box of ammo, donations are accepted by Paypal to "paypal [at]".

The software is totally free as in "free speech" and as in "free beer". I do not intend to sell or otherwise "monetise" the software, this is a hobby project; done it for myself anyway, and would be glad if it proves useful to others. Open source, GPL 3 license -- you are free to play with the code, modify it as you like; contributions are very welcome.

System requirements:

1. Latest version of a Web browser

Tested with Chrome/Chromium and Firefox on Linux, and same plus Safari on Mac. It may or may not work on Internet Explorer (theoretically it should, with versions 10 and above) -- I don't have it, and would not develop for it, or fix any related problems.

Although it is a browser-based application, a Web server is not required -- you can run it by pointing your browser to a local file on your computer.

2. Screen resolution above 1000x600

3. The interface has been designed for real computers with a mouse or a touchpad. I have tried it on an Android tab -- it does work, but the interface is not particularly easy to use. As for iPads -- I have no idea.

In short:
TARAN does *NOT* collect any data.
TARAN does *NOT* send any data anywhere.

There are no tracking cookies, no registration, no hidden "features", etc. -- all this bullshit is against my beliefs, and I personally guarantee that there is none of it, and there will be none.

If you are using a downloaded local copy of TARAN, everything remains on the computer where the browser runs.

If you are using a hosted copy from, only the web pages constituting the app are downloaded to your device. Strictly nothing is uploaded back to the server.

In future versions I may implement an automated check for updates (upon startup the application will ask the server "what's the latest version you have?"), but this feature will remain strictly opt-in (will be disabled by default, unless you specifically enable it).

Nope. I do it on my free time, as a hobby project, and offer no support whatsoever.

This being said, I probably *will* answer questions, fix bugs and introduce new features; I just don't give any promises or guarantees about that.

Feature requests can be submitted here:

I do not promise to do something about them -- there is no official support, but feel free to throw ideas, I plan on improving the app anyway.

(And of course, if you can code, and can fix it yourself -- I would very much appreciate to get a copy of the patch.)

Bug reports can be submitted here:

This being said, I fix them if and when I can (and want) -- there is no official support.

(And of course, if you can code, and can fix it yourself -- I would very much appreciate to get a copy of the patch.)

TARAN was tested using PNG and JPEG file formats -- these two are "officially" supported. In practice, TARAN should understand any image format that your browser can handle.

What's more important is the picture itself:

1. Individual shots must be visible; one ragged hole = not ok. Therefore, at most 3 shots per group at 100m / 100 yards.

2. There should be a known distance measure on target to set the scale (e.g. grid, or simply a line of known length drawn with a ruler).

3. In order to produce meaningful results, the target image should be free from geometrical distortions -- a flatbed scanner is perfect.

A photo is ok under two conditions: (a) narrow angle (big zoom from a few steps away) to avoid barrel/pincushion distortion, and (b) photo lens axis perpendicular to the target, aimed at the centre, to avoid perspective-related distortion. In other words, if using a photo, your target rectangle should be rectangle in the photo -- straight lines, right angles.

Example -- such image is not good:

(the target angles are not right, the sides are not parallel)

Example -- such image is ok:

(the target angles are quite right, the sides are more or less parallel)

4. Of course, no sights/zero adjustment between series (otherwise averaging different series is meaningless).

That depends on the definition of "validity".

The scale in the lower-left corner of the analysis pane gives an indication of the measurements quality. The confidence intervals depend on how actual shots are distributed across actual targets, but the following numbers can be used indicative guideline (give or take a few shots):

To get to minimal acceptable Level 1 quality (confidence interval is 50% of the value, poor quality), 17-19 shots are needed.

Level 2 (40% confidence interval, fair quality): 24-26 shots.

Level 3 (30% confidence interval, good quality): 45-47 shots.

Level 4 (20% confidence interval, excellent quality): 65-67 shots.

Indeed, the only information displayed about groups is:
1. Extreme spread
2. Average point of impact

Why don't I display more? Because I don't want to display bullshit.

Usually, the number of shots in a group is statistically insignificant to pull any conclusions. On "teh Internets" I have seen people thoughtfully reflecting on the form of a five-shot group ("well, it's a bit oval, stretched from top-left to bottom right") -- they call it "group analysis", what a load of crap!

This being said, ES and average PoI of a single 5-shot group are just as insignificant as any other 5-shot "statistics" -- I only display them because people love them so much, and they look cool on an exported image.

The REAL stats, with confidence intervals, are in the Analysis pane, aggregated from all shots of all groups of all targets.