Using Metric Units in AutoCAD and Land Desktop


Metric: AutoCAD Fundamentals

Metric Units in Modelspace and Paperspace

When working in metric units with AutoCAD and Land Desktop:

Modelspace: 1 unit = 1 meter

Paperspace: 1 unit = 1 millimeter

Your title block should be sized in accordance with millimeters. For example, an E size sheet is about 43" x 33". That same sheet in metric will be 1092.20 mm x 838.20 mm (There are 25.4 mm in one inch). So in paperspace, your E size sheet will be 1092.20 units x 838.20 units.

Scaling the viewports - A common metric scale is 1/200 or 1/1000. That means 1 meter on paper = 200 meters in the model space drawing. Our first thought would be to scale the viewport 1/200xp. But remember, our paperspace units are mm. So we would scale the viewport differently - 1 meter / 200 millimeter.

Zooming scales for common metric scales:

Metric Scale Zooming Scale
1:100 10xp
1:200 5xp
1:250 4xp
1:500 2xp
1:1000 1xp
1:2000 0.5xp
1:10000 0.1xp

Then when you plot, you will still be plotting 1 to 1 or 1 drawing unit = 1 mm.

 

Annotation

You have to think of your text size in terms of millimeters and not inches. The actual text size will then be the millimeter value multiplied by the drawing scale. A text size of 4mm on paper will be .004 x 500 = 2m tall in the modelspace drawing. Text conversion for millimeter text:

Size in millimeters Size in inches
2 .079
3 .118
4 .157
5 .197
6 .236
7 .276
8 .315
9 .354
10 .394
12 .472
14 .551
16 .630

 

Dimensioning

Dimscale for different metric scales:

Metric Scale Dim Scale
1:100 .1
1:200 .2
1:250 .25
1:500 .5
1:1000 1
1:2000 2
1:10000 10

All the dimensioning variables should be sized in terms millimeters. If you want your arrow size to be 4 mm on paper, set that variable to 4.

Linetype Scale

In imperial units, the linetype scale is equal to the plot scale. If your drawing scale is 1"=40’, your ltscale will be 40 when working on your drawing in modelspace, and 1 when plotting your drawing in paperspace. Unfortunately, it’s not that simple when working in metric. You have to convert metric to imperial to find the ltscale. Linetype scales for typical metric scales are as follows:

 

Metric Scale Linetype Scale
1:100 2.54
1:200 5.08
1:250 6.35
1:500 12.7
1:1000 25.4
1:2000 50.8
1:10000 254

To calculate the ltscale, simply multiply the metric scale x .0254. The ltscale in paperspace will be the same as the ltscale in modelspace.

 

Block Insertion Scale

If you have drawn and defined your block libraries with regard to imperial units, you must scale them differently for metric drawings. Typically, when you insert a block into a drawing, you scale it by the drawing scale (40x for 1"=40’, 20x for 1"=20’). With metric, you will have to scale it by the following factors:

 

Metric Scale Block Insertion Scale
1:100 2.54
1:200 5.08
1:250 6.35
1:500 12.7
1:1000 25.4
1:2000 50.8
1:10000 254

To calculate the scale, simply multiply the metric scale x .0254.

 

Metric Drawing and Project Setup in Land Desktop

After creating a project, and starting a new drawing the Load Settings dialog box will appear:

First select a metric profile to start with. On the next screen, the Units should automatically be set to Metric.

Step 3 allows you to choose the desired horizontal and vertical scale, as well as the sheet size. Here is a table to help equate imperial scales to metric scales:

Metric H. Scale Imperial H. Scale Metric V. Scale Imperial V. Scale
1:100 1:8.333 1:6 1:0.5
1:200 1:16.667 1:8 1:0.667
1:250 1:20.833 1:10 1:0.8333
1:500 1:41.667 1:20 1:1.667
1:1000 1:83.333 1:40 1:3.333
1:2000 1:166.667 1:50 1:4.1667
1:10000 1:833.333 1:100 1:8.333

 

Choose an appropriate zone in step 4 and orientation in step 5.

Step 6 allows you to choose a set of text styles to load. For metric you have two choices - milli and mleroy. Milli will allow you to choose styles based on millimeter sizes that you want to see on paper - 3mm high, 4 mm high, etc. Mleroy uses the same styles as imperial - L120, L140, etc. These styles will be sized appropriately such that your text will still be .12" or .14" tall on paper. Mleroy is probably the best way to go, because you know intuitively how tall L120 is but you may not know how tall 4mm is.

Click Next to choose a border and click Finish to complete the setup. You generally don’t have to worry about the border or sheet size here since paperspace is used.

Survey Module

If you work in the Survey module, you need to set the units to metric for this module:

File => Project Settings... => Click on the Edit button for the Survey module => Click on Units for Survey => Choose Meters

Earthworks Module

If you work in the Earthworks module, you need to set the area and volume calculation suffix’s to metric:

File => Project Settings... => Click on the Edit button for the Earthworks module

Click on Site for Volumes => Type in m for suffix down at Volume Labeling

Click on Subsites for Utilities => Type sq.m. for Square Units Area Labeling suffix and type hectare for Area Units Area Labeling suffix

Design Module

If you work in the Design module, you will need to set up Lots and Pipes for metric. To set up Lots:

File => Project Settings... => Click on the Edit button for the Design module => Click on the Lots button

Type in sq.m. for Area suffix at Square Unit Labeling

Type in hectare for Area suffix at Area Unit Labeling

To set up Pipes:

Pipes => Settings => Units...

The hydraulic units may already be set for metric. If not, you can change them here.

Hydrology Module

If you work in the Hydrology module, you will need to set the units for metric. To set up Hydrology:

Output => Settings... => Click on Units and set the units accordingly

Project Conversion: Imperial to Metric

The following outline relates to the conversion of "master" drawing files from imperial units to metric units, and the conversion of the associated Softdesk project data files. This discussion focuses primarily on obtaining the correct mathematical answers, not on the aesthetic considerations of resizing text, etc.

Drawing Size and Scale

Imperial drawings are drawn at 1 AutoCAD Unit = 1 Foot. Metric drawings are created at 1 AutoCAD Unit = 1 Meter. A line which was 100’ long would be 100 units long in an imperial drawing. If we convert the drawing from feet to meters, the line can no longer be 100 units long as that would equal 100 meters. We must scale the line down to be 100 units x .3048 m/ft. The line will then be 30.48 units long, or 30.48 meters long, which is equal to 100’.

Each design drawing (topo, plan, util, etc.) must be graphically scaled down in size to .3048 of current size.

Open each drawing, thaw all layers, turn all layers on, zoom extents

Scale all entities around 0,0,0 with a scale factor of .3048

Use the Softdesk File Setup Drawing command to change the units from Imperial to Metric and set the desired plot scale

Note: Aesthetics - Whenever the plot scale of a drawing is changed, text in the drawing may need to be resized. Use Cogo Utility Rescale to globally scale text by the ratio of old drawing plot scale to new drawing plot scale. When you resize text, each piece may need to be manually moved closer to or further away from linework and adjacent text.

 

Topo and Point Database

Aerial topo in the form of contour lines, 3D polylines, 3D symbols, 3D AutoCAD points, etc. can all be scaled from feet to meters as described above. Softdesk points, however, are at zero elevation . . . their ELEV attribute contains the real elevation of the point. When using the AutoCAD scale command, the x,y,z of the object is scaled but the ELEV attribute will not be.

Open each drawing containing Softdesk point blocks

Use Cogo Points Import/Export Points Export Points to File to send all drawing points out to an ascii text file.

Bring that ascii text file into Lotus or Excel and multiply the ELEV column by .3048. Save the Excel spreadsheet to a DOS text file.

Use Cogo Points Import/Export Points Import Points from File to bring the points back into the drawing with their new elevation. Use the Overwrite option on the import so that the old points will be replaced.

Note: Watch your layers. The points will come in all on the current layer unless you use Description Keys to control their layer by point description.

 

Digital Terrain Models

DTM files in Softdesk are stored in external databases in X,Y,Z format. Once we scale the project, the x,y,z values will no longer be the same. The TIN files will need to be rebuilt.

For each digital terrain modeling surface, open the drawing in which the topo data is stored.

Use Surface Open to choose the current DTM surface.

Use Surface Surface Data Drawing Point Data By Selection to select the points to be used in the TIN. Use the Overwrite option.

Use Surface Surface Data Edit Faults Import to import the fault lines for the current surface.

Use the AutoCAD Scale command to scale these fault lines around 0,0,0 by .3048.

Use Surface Surface Data Standard Faults By Polyline to send the new scaled down fault lines to the TIN. Use a fault description of "metric" so we can identify which fault lines are new.

Use Surface Surface Data Edit Faults Delete Faults to delete all fault lines (From File Only) that do not have the new fault description of "metric".

Use Surface Surface Data Contour Data to send out any contour lines for use in the TIN.

Use Surface Build Surface to re-create a metric based TIN from the data.

Note: Any surface editing which was originally performed on the imperial version of the tin will need to be redone on the metric version of the tin. When finished, create contour lines for the new tin to verify it’s accuracy.

Label new existing ground contour lines with metric interval labels

 

Cogo Labeling

All bearing and distance labeling will need to be erased and re-created using metric labeling defaults. Also, any dimensions such as street widths, etc. will need to be erased and re-created with metric labeling defaults. Use DDIM to control the default settings for AutoCAD dimensions.

 

Horizontal Alignments

Softdesk stores all horizontal alignment information in x,y,z format so these will need to be updated as well.

For each horizontal alignment, open the required drawing for the horizontal linework

Re-define the alignment with the same name as was used previously, but using desired metric stationing

Use the Align Stations Create Stations command to create new metric station labels, erasing the old labels before you begin

Use Align Stations / Offsets Label Station / Offset to re-label with new metric stationing any critical points such as intersections, erasing the old labels as you go.

 

Profiles

All Softdesk profile information is stored with respect to station. Now that the stations have changed due to the metric environment, these profiles will need to be completely re-created.

For each profile, open the drawing where the profile is stored.

Use Advanced Design Profile Select Alignment to choose the appropriate alignment

Use Profile DTM Surfaces Select DTM Surface to choose the appropriate existing ground TIN

Use Profile Existing Ground Sample from DTM to calculate the eg based on the new TIN

Rename the layer (probably PFGC) to something else temporarily so that information will not be erased

Use Profile Create Profile Full Profile to bring in the new profile. Make sure to insert it at the exact same location as the old profile. The routine will erase the old profile for you.

If you used the same vertical exaggeration factor in the new metric scale as you did before, you should be able to scale your proposed information (the linework on what used to be layer PFGC) down by .3048. You will then need to move that linework to the appropriate reference location on the new existing ground profile. Use Profile Create Profile List Elevations to verify that the proposed information is at the correct elevation. Then change the name of the layer back to PFGC

Re-define the proposed vertical alignment using Profile Vertical Alignments Define FG Centerline

Re-label the profile using Profile Vertical Alignments Import

 

Cross Sections

Because of the change in units, all cross-section information will also have to be re-created. Depending on the complexity of the design, the steps required here are too numerous to list in exact detail. We will assume that all users have existing knowledge of the processes involved for section design. Only the primary steps will be listed here.

For each road:

Re-sample the existing ground cross sections

Re-draw and re-define the proposed ground cross section template

Use Design Control to re-input the design parameters for Slopes, Benching, Ditches, and Horizontal and Vertical transition controls.

Erase any old plotted cross sections

Undefine the old cross sections

Plot new cross sections

Re-label any critical information

At this time, the complete roadway should be converted to metric format. Any output you desire such as earthwork quantities, import quantities, finished ground staking points, etc. should automatically be generated in metric units.

 

Pipes

The Softdesk Design Module is used to generate plan and profile gravity flow pipes such as sanitary sewers and storm drains. Use Pipes Unit Settings to change the default settings from Feet to Meters, from CFS to CMS, from Inches to CM, etc.

All pipe information is created based on the lengths of the pipe segments, multiplied by the slopes, to determine inverts, etc. Unfortunately, pipe lengths were originally set based on the stations of the manholes. Now that we have changed the units, the stations have changed. All pipe design information will have to be re-created from scratch.