Multiple Surfaces

[mtlynn]

When will Autocad let you choose more than 2 surfaces when using the multiple surfaces command.

[mjfarrell]

It already does, for sections, quick sections, profiles, and cross sections.
What is it that you are trying to do where it doesnt allow you to select more
than two surfaces?

[mtlynn]

When using the Stratum command for volumes report, you can only pick 2 surfaces.

[Aquaserpent]

I have in the past built surfaces that are composites of the total surfaces I am working with. You can do this by selecting two surfaces; make the surface that will have the other surface subtracted from it current, then past the other surface into it. Keep combining surfaces until your entire proposed surface has been created, at this point you will want to daylight to the existing surface then start your volume calculations.

[mjfarrell]

This is a 'good' thing. The reason that one is
able to use 'only' two surfaces is pretty straight forward.
Land Desktop is about to perform a volume calculation,
the thinking being that your existing ground model is one complete
surface, and that you design surface should also be one contiguous
surface. Sounds like you are building your site design using multiple surfaces
for ease of design or to get areas of various surfaces, which I have done.
However once the design is completed to the point that you need to
calculate the volumes, then you will need to compost them together into
a single design surface.
I would be interested in knowing how many issues one would encounter
if it would allow the user to select multiple possibly non-contiguous surfaces
and how would Land handle the grading between those areas?

[mtlynn]

I usually don't have the proplem, except when i need to a dentetion basin. I don't like to combine it with my proposed road contours, because it is not usually that close to the road. Thanks

[MHultgren]

With the problems LDT currently has when checking two surfaces, with a vertical face between the two, how do you think it would handle multiple vertical faces? Either sit and let you stare at the screen or pop up a message like "You have too many vertical faces in the surfaces selected to comply"?

[mjfarrell]

I usually don't have the proplem, except when i need to a dentetion basin. I don't like to combine it with my proposed road contours, because it is not usually that close to the road. Thanks

Then you should use a Grading Object for that detention basin
and use the Grading Objects properties to calculate the volume
for the basin seperately. There is even a little button that will do
just that for you.

Interested? This is usually one of the funnest part of the Land Desktop class!
Mostly when we design a 'basin' and the grading object reports the volume
as a 'FILL" as it does have some interesting quirks. You've got to see them to
believe them, and know how and why to 'fix' them up. so they read CUT.

[MHultgren]

Why not let LDt create the "Pond" for you with all the volume data included right in the label? It will give you the following
Pond name: Labels the pond name.
Average volume: Labels the pond volume calculated with the Average End Area method.
Conic volume: Labels the pond volume calculated with the Conic method.
Area: Labels the area of the pond perimeter.
Perimeter: Labels the length of the pond perimeter.
Rim elevation: Labels the elevation of the pond perimeter.
Bottom elevation: Labels the elevation of the pond bottom at its lowest point.
That is usually all the data than I require when building a basin other than the flows in and out and the riser calcs.

[mjfarrell]

Why not let LDt create the "Pond" for you with all the volume data included right in the label? It will give you the following
Pond name: Labels the pond name.
Average volume: Labels the pond volume calculated with the Average End Area method.
Conic volume: Labels the pond volume calculated with the Conic method.
Area: Labels the area of the pond perimeter.
Perimeter: Labels the length of the pond perimeter.
Rim elevation: Labels the elevation of the pond perimeter.
Bottom elevation: Labels the elevation of the pond bottom at its lowest point.
That is usually all the data than I require when building a basin other than the flows in and out and the riser calcs.


The 'only' problem with using the define pond tool, is that it does not build the
surface of the pond, it only adds that data to the hydrology database for use
later in your hydrology calculations. That and using the contours to add the pond
to the surface isn't completely acurrate due to weeding factors.
She will be much better suited to use a grading object for this process of achieving
volumes. As she probably needs earthwork volumes not pond volumes.

[MHultgren]

As you say, it depends on what she wants. I use ponds for my hydrology for the water volumes being retained \ detained by the basin. Once I get the volumes needed, then I create the contours using a grading object if the pond isn't too curvilinear. The grading object takes some getting used to when it comes to grading along a concave curve that extends the slope beyond the "Natural" radius. For example, take a concave curve with a radius of 20and tangents that are 30 feet from both ends, and grade with a 3:1 slope for a vertical difference of 40 feet and throw a couple benches in with a slope drain that is 6 ft. wide at the edge of the bench. The time it takes to clean up the contours created by the grading object can be better spent by just creating the base of the basin and using 3d offsets (create curb) to get the desired results.

[mjfarrell]

Mark,

I am totally aware of the limitations of the grading object
that you outline. You would really enjoy setting in on this portion
of my classes as I show how to resolve the problems
you discuss and more.
There are a few techniques that would prevent all of those clean-up
issue you are encountering with the grading object, that has you
resorting to 3d polylines being used to model your basins.