Contours through buildings

Totalsurv, post: 333017, member: 8202 wrote: I notice that some people run contours through buildings and walls while others don't. If you have a really large building are you not just essentially guessing/interpolating the contours if you run them through the building.

I do not show contours inside a building or retaining wall. After the contours are generated, I clip things to clean them up.

Think about your question - why would you contour inside a building, unless you did a detailed survey inside?

Ken

Ken Salzmann, post: 333019, member: 398 wrote:

Yes I agree it's just I have noticed that some drawings show the contours running through buildings as if the building is not there at all.

correct contours would run across the Roof, I call it lazy/bad work. button pushers like that have cost me clients.

My guess is sloppy cad work. I'm betting the structures were on a turned off layer when the contours were generated. If that happens on my drawings, I trim them inside the structure.

Probably just a lack of care, but having said that, there are some jurisdictions that require it as part of a slope study for the lot and they approximate a scenario where the building wasn't there.

I like to have building corners tied reflectorless. Or rather, building wall lines tied reflectorless then extended to their intersection. Then a breakline surrounding the building at ground level. Doesn't have to be right at the building line, a foot out - sometimes much more - will be fine. Doorways an exception to that.

The DTM file is a deliverable for me most of the time. My clients determine elevations by querying the DTM, not by examining contours. Instead of clipping the contours I clip the DTM. No DTM inside buildings, except in the rare case where I've actually surveyed the inside. There are various ways to accomplish that in LDT, C3d, and Carlson. But I usually just delete the TIN lines inside the breakline surrounding the building from the DTM. The contours then take care of themselves.

Peter Hughes-Davies, post: 333027, member: 48 wrote: Probably just a lack of care, but having said that, there are some jurisdictions that require it as part of a slope study for the lot and they approximate a scenario where the building wasn't there.

dashed straight line contours thru a building: OK, otherwise not

Totalsurv, post: 333017, member: 8202 wrote: I notice that some people run contours through buildings and walls while others don't. If you have a really large building are you not just essentially guessing/interpolating the contours if you run them through the building.

What do you guys do?

Unless I survey the interior of the building I would never show inside contours. There aren't any contours to show on a single floor building, and the scenario in a multi-level building would be useless.

Totalsurv, post: 333017, member: 8202 wrote: I notice that some people run contours through buildings and walls while others don't. If you have a really large building are you not just essentially guessing/interpolating the contours if you run them through the building.

What do you guys do?

If there's a contour going through a building, that means the floor isn't flat and implies the floor was surveyed. If the floor wasn't surveyed I would never show a contour through the building.

Patrick Yglesias, post: 333042, member: 337 wrote: If there's a contour going through a building, that means the floor isn't flat and implies the floor was surveyed. If the floor wasn't surveyed I would never show a contour through the building.

Yeah, but what if the floor was perfectly level and the elevation happened to be the same as one of the major contours, say 500.00 feet.

Wouldn't the entire interior of the building just be the color of just one very wide major contour, red, for example?

JA, PLS SoCal

I have seen some old houses where if you topo'd the floor, you could show multiple contours!

But contours are meant to show the elevation of the ground surface. There is none inside an existing building (unless it's just a roof with a dirt floor), so I would never show contours inside the building. Why would you want to anyway???

You might be able to make an argument for showing them inside a PROPOSED building, by I usually trim those too.

Contours are outdoor things - they don't belong indoors!

I have have had several engineers/techs indicate that autodesk civil 3D software can't understand a hole in the surface for design purposes, and they would. Have to "fix" the provided surface to use it. Traditionally I was taught to stop surfaces at buildings, or areas not surveyed, not to fake it in. I've not argued so far but seems like either a software flaw or the users not understanding it. Others have never mentioned it.

It could be an issue figuring dirt quantities in some cases (bi-level building) if the arent understanding the process.

Jerry Attrick, post: 333048, member: 1585 wrote: Yeah, but what if the floor was perfectly level and the elevation happened to be the same as one of the major contours, say 500.00 feet.

Wouldn't the entire interior of the building just be the color of just one very wide major contour, red, for example?

JA, PLS SoCal

In that highly unlikely event, I would first check the raw floor shots with rounding removed as those would probably show something like 500.003 or 499.995, in which event I would show the contour as appropriate to the unrounded measurements. In the event the floor was exactly 500.0000... I would not likely show a wide contour line as that would clutter things. Instead I would likely place the text "500.00' " with leaders to indicate the entire floor was the indicated elevation.

When the building walls go to the ground, I show contours stopping at building lines and show elevation of all entries and/or finished floor elevation.

Without underpinning and raised dwellings on poles I've shown dashed line contours inside building lines.

Some properties need specific details that others don't need, for example, a property that the runoff under the building would impact that site or the adjoining property.

If too much detail is cluttering the drawing, two different views may be necessary.

Forrest Gump summed it up well, "Stupid is as stupid does."

Some cities I work in have a slope calculation formula that asks for 'total length of all contours' as part of the formula
(to calc the maximum development area for the new construction) (California)

On these projects I let the contours run thru the buildings and and a note "contours inside of buildings are for slope calculations only"
otherwise I trim them at the building footprint

Stupid practices demanded by stupid people.

Am I an old grump today or what? Now GET OFF MY LAWN!

I ran some through some buildings only last week. Some small buildings that are going to be demolished. This was a rare circumstance though.

Usually I create a string around the building and stop the contours crossing the building.

I'm not going to criticize anyone's work, but I can tell you what I do. Since all building were built on a building pad, that let's me know a mound was probably built. I have my guys locate the breakline/drip line around the building. Then I locate the finish floor and draw it according to the split in the floor plan. Then I place a point with the proper elevation at each building corner. Now when the dtm is built, the computer program sees the breakline and building walls. Usually a contour around the building is created or atleast it shows the cliff or ridge properly.