Local Survey Data to global coordinates (lat/long)

[glanglois]

Hello all,

I'm not sure if this is a question best suited here or in the Map discussion group. Either way i'll start here. What I have is

northing/easting survey data starting at an arbitrary point. The rest of the points are measured from that.

I do know the global coordinate of the base point, but no other points.

My question is how can I take all of the points and create gloabl coordinates out of them. I assume this is possible because I know the global coordiane of our reference point, I just have no clue how to do it in CAD.

Your help is greatly appreciated!

Grant

[bingeomatics]

hello. If I understood you right, I think you must first you import you points (text file) by "Survey"  Toolspace or Menu. If you know the real global coordinates of two points you can transform it by using "Translate Survey Database" in Toolspace or Menu. There you must enter real global coordinate one of the points (which you know) and real azimuth or direction angle between them-two points.

[AllenJessup]

As Binnat said. You either need the coordinates of TWO known points or the coordinates of one and the azimuth or bearing to the other. You can't do it with just one.

Allen

[glanglois]

Thanks for your responses! Sorry it took me so long to reply. I have?successfully?created the survey database. I know multiple global coordinates for points within my survey set. I took a look at the "translate survey database" option. It does in fact as for the angle. How can this be calculated? Or is there another method to do this seeing as how I know at least two global coordinates. Also it doesn't give the option for lat/long, only the easting/northing output. Could this be because of the way my coordinate system is setup? Best, Grant

[Sinc]

There is a way to translate/rotate the Survey Database, but I find that to be more difficult than just using the Translation Tab, as mentioned above.

My favorite is to set the Coordinate System in Drawing Settings to the correct zone, then to use the Translation Tab to convert the Grid Coordinates and Lat/Long from a CSV import, even though it's not really correct.  But as long as you aren't working on a very large site, the error isn't really significant.

You can do more if you are on a really large site, especially a large section of highway/canal/etc., but you enter more difficulties.  You also may have problems if you have to export large sites out to a government agency that wants to enter the data into a GIS system.  But there are lots of problems with exporting data to anything, including older versions of C3D.  And the problems vary, depending on which version of C3D you're using, and what your client using.

[glanglois]

Ok so let me make sure i'm understanding this correctly:

My points are in PENZ format, so on the grid they are currentl easting (m), northing (m), and elevation (m).

They are in a local coordinate system, starting at a known global coordinate. (a few other points have known global coordinates)

I should assign my drawing a global coordinate sysem (lat/long) that I want the final results to be in.

Then translate the coordinates using my known points?

Also,

Let me explain what I am attempting to do because there may or may not be an easier way to do this. I want to draw a line (pipeline) from these survey points. Once that is drawn I want to impose a google earth basemap/mesh.

I'm trying to make sure that I can impose the drawing and the basemap/mesh correctly. Perhaps there is an easier way to do this?

Thanks again,

Grant

[AllenJessup]

You can't do a translation or a transformation without defining a user coordinate system based on the survey work. You probably don't have enough information to do that and it's painful anyway. What you'll have to do is use basic autocad commands to move your survey to the global system using the known point. You can then scale and rotate the survey based on the other points.

Since I don't know the quality of the other points I can't say if you should hold one or an average of all of them.

Allen