topic Re: Export a surface to a grid file in Civil 3D Forum

Export a surface to a grid file

tfitzhardinge — Thu, 01 Sep 2016 01:31:00 GMT

I have created a tin surface and need to export the surface into one of the following formats:

- .xyz

- .xyzs

- .txt (either as a esri grid format or xyz format)

- .asc

- .12da

The reason I need to export this surface into one of those format is that I need to load the surface into XPSWMM for 2D hydraulic flood modelling.

I am using AutoCAD Civil 3D 2016, using the Australian Map Grid of Australia Zone 56 Coordinates in the drawing settings.

Re: Export a surface to a grid file

autoMick — Thu, 01 Sep 2016 07:35:29 GMT

Hi,

A .xyz or .asc file is usually just an ASCII text file (i.e. the same as a .txt or a .csv) - so you just create a text file then change the file name extension later in windows explorer if needed. The XYZ format is equivalent to ENZ.

So:

- create a surface style that displays the surface vertices

- extract those points

- convert those points to COGO points

- export those points to a text file.

A quick screencast:

Cheers

- Mick

Re: Export a surface to a grid file

tfitzhardinge — Thu, 01 Sep 2016 07:53:35 GMT

Hi Mike

Thanks for the suggestion. Unfortunately the points have to be arranged in a grid like format (refer attached image) with an elevation value at each grid point. I have a feeling that Civil 3D cannot create this type of file easily.

Re: Export a surface to a grid file

Alfred.NESWADBA — Thu, 01 Sep 2016 08:20:09 GMT

Hi,

in the propector your can right-click your surface, export to dem (use file type geo-tiff).

With QGIS you can then convert the geo-tiff to e.g. esri ascii-grid.

- alfred -

Re: Export a surface to a grid file

autoMick — Thu, 01 Sep 2016 12:02:28 GMT

Yes, save as GeoTIFF, microDEM is another freeware program that can open a geotiff and export in the format you want as shown by @Pointdump http://forums.autodesk.com/t5/autocad-civil-3d-general/creation-of-dem-georeferenced-in-the-uk/m-p/6536167#M310904

Cheers

- Mick

Re: Export a surface to a grid file

TerryDotson — Thu, 01 Sep 2016 14:30:44 GMT

Beware of any operation involving DEMs in Civil3D. From what I've seen, since USGS DEMs store the elevation in integers only (no decimal), Civil3D treats at least some DEM operations this way. I haven't tested every operation and am not 100% sure, but verify you have not lost precision when you do anything with them.

If you were to consider third party software, take a look at the C3D Surface Tools on the Autodesk Apps Store. It will write a precision ESRI Ascii Grid (and a lot more formats) directly from your Civil3D surface in a single quick process (no wasting time jumping through hoops).

Re: Export a surface to a grid file

Hidden_Brain — Mon, 05 Sep 2016 13:57:04 GMT

This looks like the contents of a .ASC file. If you have access to ArcMap:
1. Export surface from C3D as landxml
2. Import landxml in ArcMap, landxml to tin
3. Convert tin to asc

This is the process I use to get C3D surface into InfoWorks ICM.

Re: Export a surface to a grid file

Joe-Bouza — Mon, 05 Sep 2016 21:26:32 GMT

Just guessing but you'll probably want to star with a grid surface. I believe that is a choice while creating a surface. Second guess: create a grid surface and paste the tin surface into it then export

Re: Export a surface to a grid file

phil.pritchardN7HPY — Sat, 20 Apr 2019 15:11:30 GMT

how do you do this, i have been trying for some time to get this working in qgis but i cant do the conversion in the latest version of qgis.

Re: Export a surface to a grid file

Alfred.NESWADBA — Mon, 22 Apr 2019 08:40:15 GMT

Hi,

please find this video showing the steps to convert DEM to TIFF:

- alfred -

Re: Export a surface to a grid file

vandenoosterkamp — Fri, 13 Dec 2019 12:47:41 GMT

I had to do the exact same task today. I placed a single cogopoint with z=100. Arrayed them 1x1m covering the entire surface. Then 'elevation to surface', dropped them on the surface. Quickselected the remaining cogopoints with z=100, erased those and then exported them to csv.