Measure volume of pond

I have used the sandbox tools to create the pond, but I do not know how to create a face in order to create a closed shape that SketchUp can can tell me the volume. I tried selecting the perimeter of the pond and cannot find a way for SketchUp to make a solid from the outline. I drew a line across the pond which then automatically created a face, but it must not have been a full face that closed the volume because Entity Info still could not give me the volume. Please help.

Click in sequence on the Scenes tabs of this SU file for ideas.

Pond volume.skp (389.2 KB)

If unsure, post you skp file here.

Pond Volume.skp (1.5 MB)
I tried intersecting the rectangle with the pond and I got a warning that one or more of the objects is not solid or is locked.

OK, I figured out that I need to right click to find the correct way to intersect with context. I was using solid tools. So now I have what appears to be a solid, although when I select it, Entity Info still does not give me the volume

I accidentally replied to myself rather than to you directly. I posted my file - without the “lid” yet created on the pond. I still have not been able to get a volume. I followed your pond sequence and seemed to get everything right, except no volume shows up in Entity Info.

I copied your group, opened it, redrew an edge which made a face to form, and ran Solid Inspector on it. SketchUp reports the volume as 33304,69 ft³
pond1.skp (306.2 KB)

Thank you. So there is a problem with the face that forms a lid on the pond shape? I drew a rectangle and intersected it with context. How can I learn how to do this properly?

Again, I forgot to reply directly to you. Sorry. Is there a problem with my pond edge that makes the creation of a “lid” difficult? You solution is different from the one offered by Jean. I wish there was a simple way to me to select the outside edge of the pond and say “create face.” Drawing a rectangle that is larger than the pond and then intersecting with context does not create a volume. There must be something wrong with my pond edge or something else.

The pond edge has some thin triangular flat faces where the original contour lines curve inwards. With the “lid” in place, Solid Inspector reports these as “External faces” as they are coplanar with the lid and are not part of the volume.

The Sandbox from Contours tool has always done these for some reason. Why, is beyond me. Basically it refuses to let the outer edge of a terrain be concave.

OK, I figure that was where the error was. I deleted those flat areas. In doing so, a lid was automatically created. But again, SketchUp does not read it as a volume. I tried selecting the lid and saying “intersect with context” but it could not find anything to intersect. I seem so close to solving this…

Click in sequence on this SU file for answers.

Pond Volume Corrected.skp (4.0 MB)

Thank you. I had to use your method of dropping the lid inside the pond rather than having it sit on top due to the unfortunate flaw in the contour that created some flat pieces. So it is not a perfect calculation since I lost about an inch around the perimeter, but it will suffice for my purposes.

Notice that in the last example, using your model, I was able to create the lid on top, so there is no lost volume.