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Zigster

Drawing objects with UTM Coordinates

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Zigster

For my course I have to learn some basic autoCAD, and for a task I've been given a rough site map (3 roads and a river making an enclosed rectangular area, there's a couple of gates and a couple of water tanks, etc) with a couple of UTM coordinates at key points.

 

Then also we have a list of UTM coords for locations where soil samples have been taken and we have to plot them.

 

Just wondering what the best way to do the UTM coordinates is?

 

Do I just use the line tool and put in the UTM of one of the points shown on the map as x and y (Eastings,Northings), and then just draw everything else in relation to that?

 

Or is there some other way that someone can recommend plotting things by UTM?

 

There's only 5 soil samples to plot, and then the 2 points on the map that are given are the corners of roads intersections.

 

But I'm wondering if there were hundreds of UTM coords that I needed to plot, could I do it with a spreadsheet or something instead of individually?

 

Cheers!

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rkmcswain

Just to clarify, are you using AutoCAD 2014?

Not AutoCAD LT, or AutoCAD Civil 3D, AutoCAD Map, or something else?

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eldon

UTM coordinates usually have lots of digits. So when you are entering these, pay extra attention.

 

UTM coordinates are mapping coordinates, but you can easily use them as plane coordinates. There is also Local Scale Factor to worry about, if you want to be accurate. If you know what Zone you are in, then the coordinates pinpoint you in the world.

 

I would have thought for your purpose, just enter the numbers (carefully).

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ReMark

eldon: Maybe you could provide the OP with an example of how an UTM coordinate would be entered at the command line?

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Zigster

Yes sorry I am using AutoCAD 2014.

 

What do I need to worry about with Local Scale Factor?

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ReMark

For what you are doing I wonder if local scale factor would be a major concern but that would depend on the nature of the exercise. What exactly is the point of the assignment? Is it using AutoCAD to plot points?

 

I believe local scale factors are applied to compensate for the earth's curvature. eldon will correct me if I am wrong.

 

Wouldn't each of the coordinates have a different scale factor eldon?

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Zigster

Here is the task.

 

The "Week 5" drawing it refers to at the bottom is just our autoCAD drawing of the site map up the top.

 

We weren't given a Zone as far as I'm aware. I'm not even sure if it's a real site anyway.

Week6Task.pdf

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eldon

As you are drawing this exercise in AutoCAD, you can probably dispense with the Scale Factor. I mentioned it because not a lot of people know about it, and completely ignore the fact that a distance measured on a plan (or drawing) with UTM coordinates, is not the same as a distance measured with a tape on the ground's surface between the same two points.

ScaleFactor.PNG

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eldon

I do not think that the person who set this question knows about mapping.

 

UTM stands for Universal Transverse Mercator and is one mapping projection.

 

After a bit of Googling:- The Geocentric Datum of Australia, 1994 (GDA94) is an Earth-centred datum, which has been adopted for use throughout Australia by the Inter-Governmental Committee on Survey and Mapping (ICSM) with all states and territories adopting it in 2000.

 

The GDA94 datum will replace the existing AGD66 and AGD84 datums throughout Australia.

 

The map projection associated with GDA94 is the Map Grid of Australia, 1994 (MGA94), a transverse Mercator projection, which conforms with the internationally accepted Universal Transverse Mercator Grid system.

 

So UTM and GDA94 are two differing systems, so how can you get one set of coordinates in two separate systems? Possibly you might get extra marks if you point out this error :shock:

 

But to return to your original question, you just enter the Easting and Northing as x and y coordinates. Just be careful because there are so many digits and it is easy to transpose figures between paper and keyboard. As the distance between these coordinates is 125 metres, you are not mapping the world.

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Zigster

Thanks eldon. I will ask about local scale factor and GDA94 next time I have class.

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eldon

One would hope that these sort of questions would be set with some sort of verisimilitude, to reflect real life situations.

 

The example is a fictitious site, where soil samples are taken.

 

GPS readings are identified as both UTM and GDA94. Whereas both these systems should give similar figures, it is tautology to mention both. What is lacking is the Zone number.

 

Usually with soil samples, it is sufficient to give a coordinate to the nearest metre. In that case, Local Scale Factor would not make a difference. But because all coordinates are given to the nearest millimetre, LSF would make a difference. Ask, in class, for an explanation as to how much difference it would make over 125.000 metres.

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eldon

I have just found out another mistake in the question.

 

As the area of the survey is in Australia, because of the GDA94, the Northings should have been labelled Southings.

 

These errors are unforgivable. Even in fantasy land, there should be a basis of truth.

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Zigster

Slightly concerning as I'm doing an engineering course and this was set by an ex geological engineer. :(

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eldon

Ah, a geologist. He probably did his surveying by pacing out the distances on a compass bearing!!!

 

I expect you will end up with something almost like this.

MaewoMud.PNG

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Zigster

Yeah he's pretty old school.

 

Also, I feel like this is a really stupid question, but did you draw those symbols yourself or do you insert them from some standard library?

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eldon

Those symbols are one of the standard AutoCAD points. Look at the Point Style.

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hossein2009

 

How can I have

Drawing two points with coordinates UTM with two different zones in autocad ???

for example 38s 736274 3712697 and 39s 332922 3707118

please hellp me!!!!!!

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eldon

I have never known a drawing with two UTM zones in it. Even when I was working in the Arctic and we had two sites which were three UTM zones apart. The earth's curvature makes drawing on a plane surface tricky.

 

I would convert those coordinates to Latitude and Longitude, and you could then get the great circle distance between them.

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