Reach

How tall is that tree? Will the wardrobe fit under that ceiling? How far away
is that wall?

Hold the phone upright and sight along its top edge — the way anybody sights
along anything. First the bottom of the thing, one tap; then the top, another
tap. Distance and height appear together.

HOW IT WORKS

Two angles and one known length, which is how high your eyes are. The angle
down to the bottom, with your eye height, gives the distance; the angle up to
the top, with that distance, gives the rest. It is a surveyor's trigonometry
with an accelerometer instead of a theodolite.

The drawing on screen is not an illustration: it is the measurement. The sight
line swings with the phone, the base leg appears when you take it, and the
thing grows out of the ground the moment there is a height to draw.

THE THREE THINGS THAT CHANGE THE ANSWER, AND THE APP SAYS ALL THREE

• **Your eye height.** It is the one number the phone cannot sense, and fifteen
centimetres of difference is metres of error on a tall building. The slider
is on the main screen, not inside a menu.
• **Level ground** between you and it. On a slope the distance is wrong, and
everything after it with it.
• **A steady hand.** Below a certain steadiness the app will not let you take
the reading, rather than hand you a number that looks fine.

And if you aim too near the horizontal it refuses: there the tangent runs away,
a tremble is worth tens of metres, and such a number would be a lie told
precisely.

WHAT IT DOES NOT DO

• It asks for **no permissions at all**. Not even the camera: you sight along
the edge of the phone, you do not look through the screen.
• No account, no sign-up.
• No servers, and no network except for the ads.

PERMISSIONS

Internet only, and only for the ads that keep the app free.

Privacy policy:
https://mindcontact.app/mcma-reach/privacy/