Deleting multiple contours at certain elevations

[Polyfreeze]

I couldn't find any way to do this, but let me explain what exactly I'm trying to do. 

I have topography in 5' contours that I need to shrink down to 20' contours (ex. Elevations:4670,4690,4710)

Is there some sort of quick selection I can use to select the elevations I need to delete? 

[Alfred.NESWADBA]

Hi,

and what object types are the contours? Do you use SHP or SDF connected via FDO or are these objects polylines on the correspondig elevation or polylines having objectdata attached, if polylines are they 3D- or 2D- or LW-polylines?

- alfred -

[antoniovinci]

No way without programming, I dare to say.

Are you sure that you really need to degrade the quality of your DTM, reducing the number of contours..?

[Polyfreeze]

They are 2D Polylines.

Sorry if my information is lacking, I'm not too experienced with cad. : / 

[Polyfreeze]

The reason I need to degrade the 5' contours down to 20' intervals is because that's what our (surface mining) pit design is based on (20' midbenches)  and we just recieved topography from our recent flight. We use our own program to update the topo, but the dxf is too big to run our current script to convert it to our "dig" files. I'm just looking for an easier way to do it. 😛

[Alfred.NESWADBA]

Hi,

a little bit FDO and you should have a chance, follow these steps:

• export your polylines as SDF (command MAPEXPORT), include the elevation as attributive value
• create a new drawing and connect (via FDO) to this SDF-file
• filter the objects displayed by the fomula
• MOD(elevation,20) = 0

you should now have only the contours displayed that have an elevation of x*20

Good luck, - alfred -

[TerryDotson]

If you were to consider third party tools, DotSoft's MapWorks Base module contains a PolyContour Delete Intermediate tool.  Simply select the polylines and specify the major contour interval (in your case 20) and it will will remove all the intermediate contours.