Contours from DEM are not aligned

[Jfactory]

I create a contour layer from a DEM raster and everytime it comes out about 700' offset from the DEM. I have no idea what to do.

[Alfred.NESWADBA]

Hi,

is it possible that you don't look from top to your data?

Try running command _PLAN with option _WORLD and see if that solves it.

- alfred -

[Jfactory]

No, it's not the view. I've done PLAN and World it doesn't change it at all. 

Also, AutoCAD crashes everytime I try to create contours into polygons.  This is really frustrating.

[Alfred.NESWADBA]

Hi,

what fileformat is this DEM? Have you tried to convert it to another format and try the same ... or have you data from another project (at least there should be samples within Map3D) just to make sure your Map is crashing every time or only in some special cases?

BTW: what version and servicepack of Map3D are you using?

- alfred -

[Jfactory]

Sorry for my ignorance but I don't know how to convert my DEM to another format also I don't know where AutoCAD has sample DEMs. My DEM is in ASCII format and it's the first time I've worked with one.

I have another ASCII DEM.  It is larger (1/3 arc compared to .53 second) and I just tried the same thing. Creat contours > polygons. and it crashed.

I'm using AutoCAD Map 3D 2013 Service Pack 2.1 64 bit. Windows 7.

[Alfred.NESWADBA]

Hi,

>> but I don't know how to convert my DEM to another format

It depends in the format you have currently, then to search the www for it.

As you have it as ASCII-format it might be a XYZ file or a ESRI Ascii-Grid or ...

>> I don't know where AutoCAD has sample DEMs

I guess you'll find DEM-data >>>here<<<

- alfred -

[Jfactory]

Different format this time... .adf. I converted it in ArcGIS. It was basically the only option I had I can't convert to DEMs it seems you need a 3D Analyst license (ESRI) to do that. 

Anyway, this picture allows you to see that it seems to be more rotated than just a translation.

This is where I got my DEM data http://www.dggs.alaska.gov/pubs/id/23964

I will go through all the tutorial data sometime I suppose but at the moment it doesn't seem very much worth my time when it seems like AutoCAD has all the things it needs to just simply make me some contours.

[Alfred.NESWADBA]

Hi,

>> This is where I got my DEM data

I tried to get the data from your link, but have not got a mail with the link yet, so I can't try it with these data.

I have it tried (to make sure) with Map3D2013 and got a correct result. The only idea now as I don't think it is a global failure (otherwise we would have read the here multiple times) is to try the same with another coordinate system or at least verify that the system of the SDF matched to the settings with the DEM

Good luck, - alfred -

[Jfactory · Accepted solution]

I hope no one minds I bump an old post of mine to say I figured out the problem.

The problem was that I had been creating the contours inside a dwg assigned to different coordinates.  I loaded the DEM with WGS-84 coordinates into a NAD-83 coordinated dwg and it was fine.  But when I made contours from the DEM they were not aligned.  When viewing the DEM in a WGS-84 dwg it is always squished in some way so I never use it, but if I make contours from that dwg, save that as an SDF, then load the SDF in my NAD-83 dwg it works perfectly.

I have no idea if this will help anyone else but I thought I'd share.