# Using Laser Distance Meter to calculate surface area of roof with minimum measurements required

Equipped with a Laser Distance Meter I am trying to calculate the total area of roofs (flat surfaces, not necessarily rectangular), and I am wondering how much data I need to collect in order to do this.

To make the data collection as simple as possible, the requirements are:

1. Only three corners of the roof need to be visible from the location where the measurements are made.
2. Each measurement gives a distance to the point that is targeted, as well as the vertical angle. Optionally a horizontal angle can be measured as well, but a method not requiring this angle would be preferred.

This should then result in being able to create a 2D Coordinate System with the roof, and being able to plot in coordinates from additional measurements.

So bottom line:

1. How many measurements are needed as a bare minimum?
2. Is measuring the angle on the horizontal axis needed?
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What is such a vertical angle, can you clarify? The roof is a convex quadrilateral or a more general polygon should we expect? – enzotib Sep 16 '12 at 15:53
@enzotib 1) I meant the angle between the line from the Laser Distance Meter (LDM) to the target spot, and the line between the LDM and a horizontal line in the direction of the target spot. Is there a correct english term for that? 2) Primarily Gambrel roofs, but hoping to be able to handle Hip roofs as well. (ref: link) – Johny Skovdal Sep 16 '12 at 20:53