The following aims to reduce some of the confusion inherent for a new user of DraftSight when these spaces are being considered and (hopefully) may even prove useful for some long-term users of Cad programs.

Paper Drawings:

Let's start with the world of paper drafting. Most readers will, of course, be fairly familiar with this but some points are worth discussing so that they can be used for comparison.

In this environment the user is limited by the size of the paper sheet on which an object is to be represented. Real-world objects are often many times larger than the sheet and therefore have, of necessity to be drawn on the paper at a reduced size. Sometimes though the object is very small and, so that its detail may be more readily seen, it needs to be drawn larger than its real-world size.

The process of reducing or enlarging the view that represents the object is referred to as “scaling”. In this process one drawing unit may be used to represent either several units in the object (scaling down for larger objects) or some fraction of a unit in the object (scaling up for smaller objects).

When parts of the object are to be shown at a different scale they must be redrawn at the new scale. When working on paper it is essential to consider, at the outset, the size of the paper AND the scale, or scales, that will have to be used to properly represent the object within the available space. When one has all the line-work representing the object (the Model) in place descriptive annotations are added and dimensioning is done directly on the model.

Sheet Space:

Cad systems have the same difficulty when it comes to outputting drawing information in a printed or plotted form. The representation of the real-world object has, in most cases, to be scaled to properly represent in on the available sheet sizes. It is also generally desirable to lay out the drawing in a manner similar to that which would be used when working directly on paper.

Most Cad systems therefore provide an environment in which this is possible. That environment is likely to be known by various names dependent on the Cad program being used. Commonly used names for this environment are “paper space”, “sheet space”, and “layout space”, and there may be others.

DraftSight favours the use of “Sheet Space”.

In sheet space the drawing sheet is shown “full size” with its content already scaled to fit the sheet. It is therefore generally printed at 1:1 since it is the sheet that is being printed or plotted.

This environment has a major advantage over paper. With paper one must place every view so that it is correctly positioned when it is first drawn and if a view proves to be incorrectly placed it must be erased and re-drawn to shift it. Sheet space on the other hand uses viewports that allow different views of a single model to be seen at different scales, one in each viewport, as if the model, or part of it, was being viewed through a hole or window in a sheet of paper. Each viewport is defined by a boundary that may be moved as often as one needs until a desirable layout of the views is achieved. It is even possible to totally re-arrange those views again later without any re-drawing.

It is at the stage of setting up viewports, and not earlier, that scaling of each view must be considered. It is also the environment provided in Cad systems for annotating and dimensioning the model (even though, as discussed later, one may choose to do otherwise). It is a particularly useful environment for working with multi-sheet, multi-view drawings.

Where it is necessary to view a part of the model at two different scales, sheet space makes it possible to do so without any redrawing of the parts of the model. They are simply shown in two separate viewports each having a different scale.

Model Space:

Cad systems have another significant advantage over paper because they provide Model Space; an environment in which the drafts-person can work on the model (the line-work representing the real-world object) using real-world dimensions with one drawing unit representing one real-world unit – that is full size (1:1). This means that the model may be drawn without any pre-consideration of scale (except when the user has elected NOT to use sheet space for layout purposes). For any model the view may be zoomed in, so that smaller objects and parts of larger objects may be seen in clear detail, or out, so that the whole of larger objects can be seen within the drawing space.

Using the Spaces:

There are two possible approaches to the use of the above-described spaces. Neither one is right nor wrong. It is up to the user to decide which will best suit the particular circumstances.

First: Using both spaces.

This assumes that model space will be used only for work on the model and all annotation and dimensioning will be done in sheet space once sheet layouts have been set up.

All work on the model is done in model space at 1:1 (full size).

No pre-consideration of scaling is necessary.

Only such line work as is required to properly construct the model (drawing) that represents the object is created within this space.

When the model is sufficiently far advanced that annotation and dimensioning is needed, work moves to sheet space.

Again work is initially at 1:1

Here a sheet layout will be created for each drawing sheet that is required in the output when printing / plotting. These may all be one size or there may be several different sizes and different printers / plotters may be used for different sheets. The sheets may be set up one at a time as they are needed or set up based on layout pre-planning.

Each sheet appears on a separate tab that may be re-named as needed. Each sheet also needs a Print Configuration that defines its properties . Right-click on the sheet tab and select “Print Configuration Manager... ” to open a window where a configuration can be selected (when it exists) or set up (when it doesn't).

Each sheet may have a border and title-block added at scale 1:1.

Note that it is quite possible that any drawn border will not properly fit the sheet for which it is intended until the print configuration is properly set up and activated.

All detail, including annotations and dimensioning, is added to the sheet at scale 1:1.

To see the required views of the model one or more viewports will be needed on each sheet – one viewport for each view of the model. A default sheet will most likely show one rectangular viewport when it appears. That viewport probably needs resizing, after the sheet configuration has been set up and applied, by selecting the viewport boundary and dragging its grips (blue highlights) until it suits the sheet size and view layout. The first viewport may be copied to create more viewports on the same sheet or new viewports can be created as described in DraftSight help [F1 (help) > INDEX > VIIEWPORTS ON SHEETS].

When a viewport is set up it may show all, only some, or none of the model depending on how the two initially align with one another. The following procedure will help find the part of the model you want to see:

Double-click inside the boundary of the viewport. The boundary will thicken indicating that the viewport is active and that the model can now be accessed and worked on through that viewport.

Select VIEW > ZOOM > FIT. The whole of the model should now be seen in the viewport.

Zoom in on the model and/or adjust the viewport size by dragging its grips until the part that is needed begins to look about right in the viewport.

Alternatively, delete the default viewport and create a new viewport, or viewports, using VIEW > VIEW TILES > and selecting an option from the second group of options.  Each viewport will show the whole model and the viewports may be set up from there as described above.

Scaling a viewport:

Because both the model and the viewports on the sheet layout are drawn at 1:1 using real-world sizes, the view of the model will almost always need to be scaled as follows:

Note: while working on the viewports it is useful to set length units precision to at least 3 decimal places so that the display of small scale factors is not unduly truncated. [From the menu select FORMAT > UNIT SYSTEM... and make the needed settings.]

Make sure the PROPERTIES palette is showing and displaying icons and labels

[If necessary, Right-click in a blank part of any toolbar and select “Properties” to display it. Then right-click in the displayed window and select “Display icons and labels”.] .

With the viewport active (or its boundary selected if it is inactive), go to the PROPERTIES palette and in the “Misc” panel find “xn Custom scale” and “xn Standard scale”. The former will always show the scale factor – a number which may be less than, equal to, or greater than 1; the latter will most likely show “Custom scale” but may show a standard scale ratio. If a standard scale ratio is found then start from there and use the associated drop-box to make changes. Otherwise use the “Custom scale” area and, starting from the value that is there, enter a new scale as either a scale factor or a scale ratio as a fraction (DraftSight won't recognise the ratio form at this stage).

Examples: scale ratio 1:20 => scale fraction 1/20 => scale factor 0.05; scale ratio 3:1 => scale fraction 3/1 => scale factor 3.

Once the viewport is arranged and scaled as needed, go to the PROPERTIES palette and in the “Misc” panel set “Display locked” to “Yes”. This will prevent accidental zooming of the viewport and consequential loss of correct scaling.

If any change is made to the model that affects any part visible in a viewport that change will immediately show in all affected viewports.

Once all viewports on the sheet are properly set up annotations and dimensions may be added and the sheet is ready for printing.

It is important at this stage to remember that

• Entities visible through the viewport that are part of the model are still in model space and only accessible by either returning to model space or accessing model space through the viewport after the viewport is activated, and

• Annotations and dimensions relating to a view in a viewport are entities in sheet space as is the viewport boundary itself.

If that boundary subsequently needs to moved, all related annotations and dimensions will need to be selected along with the viewport boundary or their relationship to entities of the model within the viewport will be temporarily lost until the error is corrected.

Second: Working only in model space.

Cad systems are flexible and it is therefore possible to work totally in model space adding annotations and dimensioning in that space and then printing from there - provided appropriate scaling of details is done and other necessary settings are properly made within the program.

Again the drawing usually starts with the model at scale 1:1.

Before any annotation, dimension, border, or title-block is added, the size of sheet to be used for printing has to be decided and the scale at which the drawing is to be output to the sheet calculated.

Example: A4 (297 x 210 mm) drawing sheet in landscape orientation; Drawing overall 6000 mm wide x 4000 mm high – note that all measurements are in the same units.
Scale ratio = 297:6000 = 1:20.202 to fully fill the sheet so use 1:25 (or even 1:30, 1:40, … ) to allow reasonable peripheral space.
Scale = 1:25 => Scale fraction = 1/25 => scale factor = 0.04 (1 divided by 25) => inverse scale factor = 1/0.04 = 25 (or inverse of 1/25 = 25/1 = 25).
Check height: 210:4000 = 1:19 so 1:25 may be a good choice.
Note that had this been 1:[much more than 19] then height would have quite likely dictated the scale ratio actually used.
(A similar calculation using the dimensions of the known space can be used when the drawing is to occupy a known space within the sheet.)

For a single sheet, single view drawing the elements making up any border, title-block, annotation, or dimension must now have their required final sizes multiplied by the inverse of the scale factor so that they will appear on the screen in proportion to the model and be printed at the required size on the printed sheet after the drawing is scaled to fit the paper.

For text and dimensions this may be done via “styles” [FORMAT menu]. Separate styles are needed for each different scale that will be used in the drawing set with scaling adjustments made thus:

Text: Specified height = Required output height x inverse of scale factor

Example: for 2.5 mm text height at scale 1:25, Specified height = 2.5 x 25 = 125 mm.

This may be specified on each occasion that text is inserted or may be set up in a text style that has the text height set to the specified height. The first option allows flexibility of text height by simply specifying different heights as needed at the time of inserting text, while the second method requires a different text style for each different required text height. Changes of text height may also be effected through the properties palette.

Dimensions: Scaling of all elements used in dimensioning may be handled with a dimension style using the same principle as for text. In this case the inverse of the scale factor for the sheet is used to set the scale of dimension elements via FORMAT > DIMENSION STYLE... > FIT > DIMENSION SCALE.

That sheet can then be printed at the pre-determined scale.

Other single sheet, single view, sheets can be similarly prepared and printed using different scales as appropriate.

When detail views are to be added on the same sheet as a main view they will often be …, 2, 3, 4, 5, … times larger than the main drawing. In this case the entities that make up those views must be duplicated by either re-drawing, or (better) copying from the model. In either case they must be scaled up by a factor that will achieve the required enlargement. All dimensions that are reported when those new entities are dimensioned will then be larger than real world sizes by that factor.

This can be corrected by using a dimension style in which the “linear dimension scale factor” (ldsf) is set to the inverse of the enlargement factor so that correct real-world dimensions are reported when dimensioning is done using that style.

Example: 10x enlargement; ldsf = 1/10 = 0.1

Note that the new dimension style must be activated before it will have any effect.

Alternatively, once the new style is created, the new dimension style may be applied to an individual dimension, or group of dimensions, by selecting that style from the drop-box of the “Misc” panel “Dim style” entry of the Properties Palette while that dimension, or group of dimensions, is selected. This will have immediate effect without affecting the currently set primary dimension style.

As for any paper drawing, annotations that specify the scale of a view will need to show the scale at which that view will appear on the sheet when the sheet is printed.

Example: Main drawing to be output at 1:25; annotation would show “Scale 1:25” (without quotes).

10x detail; annotation would show “Scale 1:2.5” (without quotes) since 25/10 = 2.5.

It should be evident that as the drawing becomes more complex so the amount of user computation, and consequential risk of computational error, becomes greater. For this reason along, with others not mentioned here, many users restrict this method to relatively simple drawing sets.