Clean Unnecessary Points - New Feature

 This article was written to describe a new feature that will be included in the release of iMapIt`s version 4, to illustrate it and bring understanding of its use.

“Clean” is a quick way to purge unnecessary parts of a mapping measurement. When we collected a large number of points and we would not necessarily need all those points, we can clean them automatically.

Observe, for example, the measurement shown in the image below, of an approximately rectangular area, where we had collected a coordinate for each of the small blue dots highlighted.

Note that there are several points that apparently are part of the same line shape. In the example above there are only a few points. But imagine measurements with hundreds or even thousands of points and where many of them could be removed without prejudice to the contour of the area. We would save a lot of space not only on our equipment, iPhones and iPads, but also transfer time and further processing time if we were to take these measurements into other software.

What if we could have a quick way to remove these “unnecessary points”, obtaining a measurement with the same contour and with fewer points, as shown in the figure below?

This is the goal of this new function called “Clearing Unnecessary Points”. In version 4 of iMapIt it will appear among the many other new functions available for handling a feature shape.

And how does this new function work?

Setup:

In this new version, a new option for automatically collecting coordinates was introduced, which collects a new point with each change of direction in your displacement. This type of automatic collection due to changes in the movement direction introduced a new parameter: an angle of inclination. This angle defines the limit that iMapIt can accept between the previous line segment collected and the new one that is about to be created while you are moving. A new coordinate will be collected when this angle is reached.

This angle is defined in the settings screen and can be changed at any time as needed. The image below presents this new functionality in the settings screen.

The “Clean” function uses this same angle to do its job. Above we see the standard angle that is initially defined: 1^o30’ 0” (one degree and thirty minutes) of inclination.

Its logic:

Note that each feature is made up of a sequence of points. When the feature is of the “Point” type, the collected points are presented individually. When the feature is of the “Line” type, the points are concatenated in the sequence in which they were collected, so that they form a line. And finally when the feature is of the “Polygon” type, just like the “Line” type, the points are concatenated in the sequence in which they were collected, so that they form a line, but the last point is automatically joined to the first so as its shape becomes a closed polygon, which defines an area.

Also note that for the “Line” and “Polygon” feature types, each line that forms its outline is formed by a sequence of straight lines segments. Each line formed by two consecutive points. These line segments form angles to each other, as shown in the figure below.

The “Clean” function eliminates points that are between two lines that form an angle smaller than 1^o 30’, or any other angle that is defined. Thus, the feature will have fewer points to represent a shape very similar to the previous one.

Before

After

This function does not change the original feature. It creates a new feature where the “unnecessary points” have been eliminated. If you are satisfied with the result and no longer need the original feature, you can simply delete it.