How to find the corners of a trapezoid?

Thread Starter


Joined Oct 3, 2010
it is not necessarily a trapezoid . . . depending on your camera angle and distance . . . and optical network
The problem, the question, the solution, has to start somewhere. The bounding shape of the container in the OP was a trapezoid, so that's where I started.


Joined Sep 30, 2009

Thread Starter


Joined Oct 3, 2010
Your quoted portion refers to 2 different things.

When I said "Smaller overseas orders go into bags on pallets" yes, what you linked to is what I was referring to. Except the bags we use are taller, reaching almost to the ceiling of a shipping container.

When I said "for overseas shipping, bulk orders go into lined containers" I was not referring to some special container. It is an ordinary container lined with a pre-made liner similar to this:

Just a giant poly bag with the same dimensions as the interior of the container. The crew installs the liner and then blows the product into it.

That seems like a better idea for your company and the buyer. If I understood you your making special lined containers. Won't that be expensive up front and to ship them back empty?
This is not for my company. I do still have my own company but it is relegated to a side gig for the time being. This is for my "day job." And my employer is not so concerned about what is best for the buyer; we are not paid by the buyer. The big chemical companies who produce the raw plastics sell to the buyers. They just don't package or ship their own product; we do. Railcars full of plastic leave chemical plants owned by Dow, BASF, Lyondell, etc. And come to us. Those companies are our clients and we package the product according to their instructions (pallets of small bags, pallets of bigger bags, Gaylord boxes, shipping containers, bulk trucks, etc) and send them to the address they tell us. I'm not sure if we even know who the buyers are, until the address is provided. More often than not (especially now) the product does not have a buyer when it arrives, so we package it and store it in our facilities until the client finds a buyer and we are given the order to send it.


Joined Apr 2, 2020
The container liners can be fitted into any container, they are clean inside and pellets are sucked and/or blown out (sometimes the container is tipped as the pellets are blown out.
The customer is supposed to remove the liner, roll it up and store it until they have enough empty ones to fill a container for a return shipment (ideal situation). And the empty containers are put back into general circulation.
Sometimes, customers ship it right back for a refill. Shipping container rates are really high right now. Lots of optimization going on.


Joined Jan 6, 2004
Hola @shortbus
In fact the container built and so certified as per ISO standards is a concept implemented to require standard tools and procedures for handling and transportation. From the crane driver POV the content doesn't matter.

Then it comes what you wanto to do with them.

With very similar concept as shown by @strantor, they export wine in 20 footers. Called ISO tanks in the jargon.

If you are curious, you could search: platforms, flat racks, standard box, high cube, open top, tanks, reefers, TEUS, FEUS.

The 45 and 53 is variation not seen usually loaded in ships.

Won't interfere this thread again. Promise