Inputting Points Using Lattitude and Longitude

I have to input several points into an Autocad drawing. The coordinates for these points are given in lattitude and longitude. Is there any simple way of entering these or converting these points to X,Y coordinates?

The area is rather small, and it does not have to be very accurate, so the curvature of the earth can be ignored.

Thank you

 

You have an example? or a excel table?

 

If your just using vanilla AutoCAD I'd suggest Googling up CORPSCON. Its a
free program compiled from stuff written by the Corps of Engineers. It will
process a batch file containing Lat-Long's. You can select which State Plane
system you want. If that doesn't matter just pick one at random. That will
give you X,Y that you can either enter or bring in using a script file.

Allen

for these points are given in lattitude and longitude. Is there any simple
way of entering these or converting these points to X,Y coordinates?

curvature of the earth can be ignored.

 

Are you running vanilla AutoCAD?

With AutoCAD Map it's pretty easy - plot the points in one drawing in lat-long coordinates, save and attach that drawing from a new one in your desired coordinate system, and query the data.

 

Ekubaskie

I do not know what "Vanilla Autocad" is so I probably do not have it. I have standard Autocad and Autocad map.

Your suggestion about entering the points in latitude-longitude coordinates is exactly what I want to do, but I do not know how to enter them.

I have read the help files and figured out how to query the data into a new drawing as you suggested. But I do not know how to begin by inputting the points in latitude-longitude coordinates.

Thank you for your help.

 

Its just like drawing a line without picking the points. You need to set
your units (Angle) to degree/min seconds. the draw like the following
example:
if you need a line that is 135 feet at 62d51'35"E
you would type it like this:
pick any point to start,
@135'<62d51'35"E

you can start your point at 0,0 or any point. just remember to have the @
symbol

 

How the name of one of the most sensuous flavors/scents in existence came to mean "ordinary" or "plain", I just don't know - but that is what the expression means; i.e. Standard AutoCAD.

You're almost there. The correct lat/long system depends on the source of your points. If they come from GPS, use WGS84 datum, Latitude-Longitude; Degrees.

Latitude is X, Longitude is Y, with West Longitude negative. Both need to be input as decimal degrees, not as degrees-minutes-seconds.

Draw your lines or points using the decimal lat-long as X-Y. I find points difficult to identify later, so I usually to text objects (very small, height about 0.001) with their insertion points at the lat-long point, and the actual text is for identity; i.e., "P1" for "Point 1".

 

Konstantin,
Take care. All the advice available on the NG's is not necessarily
knowledgable. Latitude and Longitude as you probably know are
in degrees and cannot be entered as x and y coordinates. Each
degree of latitude is approximately 60 nautical miles (69 statute miles).
It varies slightly due to the curvature of the earth (as you know) and
near the north pole a degree of latitude is 69.407 miles and at the
equator it is 68.703 statute miles.

A degree of longitude is widest at the equator at 69.172 miles
(111.321) and gradually shrinks to zero at the poles.
At 40° north or south the distance between a degree of longitude
is 53 miles (85 km). To determine the distance between degrees
of longitude at a particular latitude, you need to use the cosine
function.

Length of 1 degree of Longitude = cosine (latitude) * length of degree (miles) at equator

There are calculators available that use approximate calculations (fixed latitude
dimension) to determine the distance between two points.

These distances are also only relevant at mean sea level.

Example:
http://www.wcrl.ars.usda.gov/cec/java/lat-long.htm

If you want to enter points as coordinates on the earth you could treat
the points as spherical coordinates from the center of the earth. The mean
radius of the earth is 3959 miles. You could enter the points directly as

3959<longitude<latitude

That format demonstrates spherical coordinates. After drawing the points, you
should be able to measure the distances and choose a view that is normal to a
plane containing 3 of the points. Then you could use projection to flatten them
to X, Y values.

Regards,
Doug

 

I would suggest converting the Lat Long to a parallel plane coordinate
system. I use Corpscon...
http://crunch.tec.army.mil/software/corpscon/corpscon.html
Then you can enter the points as X,Y.

Which system to use depends on what your trying to do with the data.

Allen

 

Thanks for the link Allen.

 

AutoDesk desighned the LatLong coordinate systems in Map, LDT, and Civil 3D to perform just as I described. Certainly any linework looks massively distorted if you view the latlong drawing, but that is NOT relevant to the question at hand.

What IS relevant is the result, and I have used the method many times to bring GPS data into drawings. Known points fall onto their State Plane or UTM coordinates quite within the GPS equipment's accuracy.

I have also used it to bring in boundary lines for USGS quads and then matched the rasters and had the township & section lines and streets line right up with GIS and CAD mapping. (USGS world files, at least for my area, are not accurate to enough significant digits for accurate placement.)

 

Yes. Your correct. I was only offering an alternative. This will also work.
I don't view having choices on how to accomplish a task as a bad thing.

"quite within the GPS equipment's accuracy" Which GPS equipment?

3D to perform just as I described. Certainly any linework looks massively
distorted if you view the latlong drawing, but that is NOT relevant to the
question at hand.

bring GPS data into drawings. Known points fall onto their State Plane or
UTM coordinates quite within the GPS equipment's accuracy.

matched the rasters and had the township & section lines and streets line
right up with GIS and CAD mapping. (USGS world files, at least for my area,
are not accurate to enough significant digits for accurate placement.)

 

In a way, we were both suggesting the same thing, considering that the LatLong coordinate systems in Map ARE parallel plane coordinate systems.

 

Thank you for all of your help. Ekubaskie, I have it solved using your method. Thank you also Doug Broad. My boss, although a nice guy, is not the engineering type. He just "knew" there must be an easy way to enter latitude-longitude into Autocad. After I printed your message and let him read it, he now believes me that it is no simple thing.

 

Glad to help. Somehow I missed the fact that you had AutoCAD Map.
If Map weren't available, it seems like it would be a relatively simple
task to write an input program to convert coordinates from lat,long to
x,y.

 

Likewise - once you get the idea, Map starts to make sense!

It would be a bit of work without Map - the conversion from lat, long to state plane or UTM is not a simple formula. The problem is made even worse by the differences in datum. Then there are different formulae for dealing with NAD27, NAD83, or WGS84 (GPS) for lat-longs, and 27 or 83 for state plane or UTM, as well as feet or meters. All of this is already figured in with Map once a drawing's system is set.

Here in Anchorage, Alaska the difference between NAD27 and NAD83/WGS84 is about 450 feet. I spent a half-hour this morning explaining that to an engineer from another firm when they plotted a series of wind-generator towers out in the ocean instead of atop the bluff.