area information

Hi, Is there a way to calculate the area of a closed polyline?
I can only find the 'polygonal area' tool which, as far as I can see, requires you to draw a new closed polyline each time. But I want to be able to click on shapes / areas I have already drawn and find out the areas (square metres), without have to effectively trace over them again.
Can anyone help me? Thanks!

If you do a hatching on a closed polyline the hatching area is given in the command line.

Thank you very much. That is certainly useful!
By the way I am quite perplexed that it is not easier to calculate areas on LibreCAD. Being able to quantify the spaces that you are drawing is an essential part of architectural and urban planning work.

Hi sungam,

Don't be perplexed.  LiberCAD is an open source program written by volunteers.  It is free and as such does not have all the bells and whistles found in commercial packages.  I am neither an architect nor an urban planner and rarely need to know the area of any shape.  While having the ability to measure space would be a good feature, it may be that there just isn't enough demand for it from the general community.

Anyway, welcome to LiberCAD and the forum.

Hi again sungam,

I did some looking and there is a way to easily find the area of a polygon.

Select Tools/Info/Polygonal Area.  Then select the points of the polygon and the total area will be given.  I am using version 2.2.0-rc1-31-gac524db on Linux Mint.  

Hi

I was just wondering if there has been any work done with LibreCAD regarding showing the Area? I have the same question as the OP, raised back in 2018. I have traced an area using Polyline and now I need to know the area within it. Re-tracing the shape a second time when it is already a single entity seems a bit redundant

The second issue I have is the area I'm trying to define is a plot of land. Because my units are in millimetres the number is too large to show and ends up displaying as Area: 1.14423e+08 Millimeter^2. Is there a way I can change the units on a per entity basis rather than having one unit covering the whole drawing?  

There is no dedicated tool to measure the area of a closed shape. But you can use the hatch tool on an extra layer. The hatched area then is indicated in the command line.
But beware, the result maybe wrong if arcs are involved. Fixed in latest development versions.

No you can't change units on a per entity basis. A workaround for your problem could be to make a version of the whole drawing scaled down by factor 0.001. Thats equivalent to meters then, appropriate for a plot of land.

I added the algorithms to find the enclosed area in 2.2.1 and master branches:

1, the algorithm is expected to be robust, so it can find areas with holes (say, lakes), and all the way to recursively with islands and lakes(say, islands on lakes, for example);

2, I didn't create a new GUI method to find the area. It's not difficult to do so though;

3, I am thinking about adding GUI methods to all using enclosures by intersections as well, so not limited to start/end points at contour connection points.

Clearly, the last point requires some engine work with a new type of hatch objects.

Any help is welcome.

I will see whether we can join gsoc again, with hatching, paper space/views, as potential projects.

dellus wrote

There is no dedicated tool to measure the area of a closed shape. But you can use the hatch tool on an extra layer. The hatched area then is indicated in the command line.
But beware, the result maybe wrong if arcs are involved. Fixed in latest development versions.

No you can't change units on a per entity basis. A workaround for your problem could be to make a version of the whole drawing scaled down by factor 0.001. Thats equivalent to meters then, appropriate for a plot of land.

Currently, in 2.2.1 and later, hatching area is calculated by analytical algorithms, meaning precision to 10^-8 or better.

Yes, it's currently required to create a hatch to use the area calculation (aside from the polygon area method), the hatching method is designed to support areas with edge curves of the types: lines, circle, ellipses, parabolas etc.

More work is needed to get this feature user friendly.

sungam wrote

Thank you very much. That is certainly useful!
By the way I am quite perplexed that it is not easier to calculate areas on LibreCAD. Being able to quantify the spaces that you are drawing is an essential part of architectural and urban planning work.

Thanks for the replies everyone. I ended up rescaling the drawing as suggested and that allowed me to hatch the areas I was interested in