Area measurement.

[smccrary@rosemccrary.com]

Greetings,
I am confused about how PDF-XChange Editor calculates area using its Area measure tool.

In the attachment, note that the object's width and height are 0.55 inches and the scale is 1"=100'.
That would mean that the true size of the object is 55' x 55' with an area of 3025 SF (55x55).
But the Area tool shows an area of 2987.2 SF, so not equaling 3025 SF gets me a bit concerned about the calculation.

At first I wondered if the border line width would impact area, so I changed it from 1pt to 0pt, but no change.
However the Width and Height did change to 0.606-in square for a 1pt border width, so the area should show 3672.4 SF and not 2987.2 SF.

Even so, the width of the border line in the attachment is 0 pts.

Could I please get some clarity on this?

Also, I am curious to know if anyone else thinks that the dimensions of an object should change with its border width.
Coming from an engineering background, the width of a line is independent from the lines dimensions. This becomes an issue with 2D and 3D shapes and the calculations of area and volume. Different software packages handle this issue differently, some (like AutoCAD) prefer to hold the center of the line as the true measure. Others, like ArchiCAD, will allow the user to define the measurement point. Nevertheless, it is not obvious to how this is handled in PDFXE.

Thank you.
Steven McCrary

image.png

[Sean - PDF-XChange]

Hi Steven,

I can see and understand your concerns, and I have passed this case on to the team to take a look, as it's certainly perplexing - we will have an answer for you on Monday.

Also, you are correct that dimensions of an object are completely independent from the border width.

Kind regards,

[Sean - PDF-XChange]

Hi again Steven,

I have spoken to the development team about this and they have confirmed that there may be a slight programmatical bug here that makes it difficult to perform measurements with rectangles. They will take a closer look into this soon. They also suggested telling you that the best way to ensure rectangles and other annotations are created as accurately as possible is to ensure that you have the snapping feature and grid enabled when you are creating these items. You can activate those settings in the UI as detailed below:

Untitled-7.png

I hope this assists you in resolving the issue - if you have any further queries please get in touch.

[smccrary@rosemccrary.com]

Greetings,
Thank you for looking at that.

There are a couple of very simple algorithms for calculating polygons:
one is called Double Meridian Distance as illustrated at this web page:
https://civilengineering-softstudies.com/582-area-of-traverse-using-dmddouble-meridian-distance-method.html

But, I prefer this one, often used in COGO programming, called Area by Coordinate Method:
https://www.mathopenref.com/coordpolygonarea.html

Thank you.

[Sean - PDF-XChange]

Hi Steve,

Apologies, my previous post was somewhat unclear. The Rectangle and Area tools are working exactly as they should be within the software. The reason that you see a difference between the dimensions specified in the transform selection dialog box (0.55 inches x 0.55 inches) and the Area Tool output box, which shows 2,987.18 ft squared in your image and not the 'expected' 3025 ft squared (i.e. 55 feet x 55 feet as per the scale of 1 inch = 100 ft) is because the Transform Selection dialog box and the Area Tool output box are referencing different data in the document. The Transform Selection dialog box is referencing the 'bounding' box around the rectangle annotation (including any border width specified in the annotation properties), and the Area Tool output box is referencing the rectangle itself (excluding any border width specified in the annotation properties). Note that the rectangle in your document appears to be slightly irregular, and the lengths of the sides do not match perfectly. If you use snapping you can make perfect rectangles, and if you set their border width to zero in the annotation properties, you will find that the measurements given in the 'Transform Selection' dialog box match those given in the Area Tool output box, as in that case they are referencing items that are exactly the same size:

Untitled-12.png

I hope this clarifies the issue for you.