How to Draw a Survey Curve in Autocad
Architectural Technology
CADD12384 - Architectural Drafting 2- CAD
Each arc should have an arc Length, a chord length, a chord bearing angle, and an arc radius.
Arcs on property lines are defined by the chord, which is the straight length between the start and end points of the arc.
To draw the plan, replace the arcs with lines (use the chord length and the chord bearing angle). You draw the arcs in afterwards.
When planning to draw the property lines, ignore the arc. Imagine you have a straight line (the chord) with a length (the C value) and an angle.
After the property lines (and the chord) are drawn, add the arc. Use the ARC command, Start, End, Radius option.
After drawing the arc, use the LIST command or select the arc and look at its properties to see the arc length. Compare it to the (A) value on the survey.
Delete the chord.
Entering degrees:
Use surveyor's angle units to enter the data.
Instead of a degree symbol, enter the letter 'd', and remove any spaces. You can enter angles in uppercase or lowercase; N is the same as n.
For example:
N 47° 17' 10" E
should be entered as
n47d17'10"E
If you wish to try the sample metric siteplan, download it here.
Steps:
- Hold the printout of the site survey so that North is facing up.
- Study the site.
- Identify the distance and bearing angle for each straight line.
- For each arc segment, find the Arc Length, the Chord length, the chord bearing angle and the Arc Radius.
- Decide on a starting point (preferably where two lines meet).
- Check the direction of the lines you will be drawing. Does it match the bearings on the survey? If not, reverse the direction of the bearings.
- Begin a new metric drawing in AutoCAD.
- Set UNITS: for this drawing we will need Length units to be decimal, with 1 decimal precision or better, and angle units to be set to Surveyor's units with a precision of 1 second or better.
- Set LIMITS: for a survey, a good guideline is to set the limits to roughly double the longest line. So in our case the limits will be from 0,0 to 60000,60000.
- ZOOM ALL. The limits now fill the display.
- Create a layer named ASPProperty. Set the layer colour to Cyan and set the layer linetype to Phantom2 or Border2.
- Make layer ASPProperty the current layer.
- Set the annotation scale to 1:200. Note that you may need to click on 'custom' and add the scale 1 to 200.
- Verify that MSLTSCALE is 1 and PSLTSCALE is 1.
- Start the line command and click a point to start. Enter each line using the following syntax:
@distance<bearing angle
@ means "last point", and < means "using angle of".
So for example the first line on our siteplan would be:
@2030<n34d03'48"E
Note that we entered the length in mm (2030) instead of m (2.03).
Continue entering the data:
@9310<n47d17'10"E
@30000<n42d42'50"W
@10100<S47d17'10"W
Note that this line is not going NE but rather the opposite (SW). To flip the direction of the angle, you change both letters.
@3990<s40d54'23"w
@30150<S47d59'56"E - Zoom in on the starting point, and measure the distance between the start and end points. The distance should be small (a few cm).
Note: Meters or Millimetres? Since AutoCAD uses mm as the base measurement when scaling in paperspace, we should use mm as well.
- Zoom in on the upper left corner of the site.
- Using the given radius and the Start, End and Radius arc options, draw the arc.
- Pick one endpoint of the chord.
- Pick the other endpoint of the chord.
- Enter the radius (17940).
- Check the arc length:
- Select the arc.
- In the properties palette, look for the arc length.
- Verify it is the same (or very close) to the arc length on the survey.
- Erase the Arc chords.
(note: if the arc is drawn wrong, reverse the order of the start and end points (possible), or try entering the radius distance as a negative number (very rare).
Source: http://trantor.sheridanc.on.ca/webct/cadd31a2/content/Drawing-propertylines-with-arc.html
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