Recreating Size and Measurements From Images

Many of us DIYers we see something on a blog, a post, or a commercial site that we would like to try or make our own version of it, but there are no plans, measurements, or size given on the site. This Instructable is intended to give you some ideas of how to recreate the sizes and measurements from the images you find to create projects you find online and hope it will help you recreate them and improve them in your own way.

Step 1: Find Something You Want to Recreate

You find yourself browsing the internet and looking at all the cool things other people have made, things for sale but you want to make improvements in, or you just want to try you hand at building it yourself. You go to their website and look closely at their images and find lots of descriptions about what it is and how they use it but nothing about how it was made, and no patterns. So you start thinking, "I want to make one like that but I would really like a plan or some measurements to start from."

There are some amazingly smart people who can take a look at something and will just build it hit or miss on the sizes and everything just works out. But if you are like me and don't have the instantaneous knack of mentally reproducing unseen measurements in your head, or don't have the resources to be able to build hit or miss this will help get a basic guide on how to reproduce some of the measurements and get a basic plan together.

I found a portable wooden Viking house on this SCA site and this ancient Chinese crossbow action I wanted to reproduce for my own projects. So I will show you some examples of how to use a few techniques to get measurements from an image.

Step 2: Using What You Know

When I found the viking style tent/cabin on the SCA site I was looking at what I could see about how it was constructed. First, I was thinking it was made of 2" x 4"s which are really only about 1 1/2" x 3 1/2". 2" x 4"s are common, easy to get, so it made sense initially. They are also a known size which we can use to figure out the design.

I counted how many boards there were on the visible side, luckily they alternate long and short so I don't have to try and find each board gap in the photo and hope I don't miss one or double count. There were 40 boards on a side. I then calculated using the actual size of 2" x 4"s (1.5" x 3.5"). So 40 boards at 3 1/2" wide would make one side about 11.67 feet long.

((40 * 3.5")/12) = 11.66667 feet

This seemed much longer than what is seemed in the photo. Now due to the angle of the photo it could have foreshortened the length of the side and it could be that long, but something just wasn't fitting to my eye.

I then took the average weight of a 2" x 4" at 1.28 lbs. per linear foot, and calculated what the one visible side would weigh.

(40 * (8' * 1.28 lbs)) = 409.6 pounds

So the total weight of just one side of this portable cabin tent is about 409.6 lbs. The real weight would be a bit less than that since half the boards are cut down about 1 foot. And that is without any connecting boards or screws added in. Trying to wrangle just one side is quite the task for a portable structure.

I then ran the numbers for using 2" x 3"s (1.5" x 2.5").

((40 * 2.5")/12) = 8.3334 feet

(40 * (8' * .94 lbs)) = 300.8 pounds

The length seems to match the size of the side better to my eye, but the weight is still a bit much for a portable structure.

So start looking closer at the photo. I noticed the end of one of the connecting boards is visible on the underside of the far wall. The thickness of this board seems much thinner than what I would think of for either a 2" x 4 or 2" x 3", but the 3" dimensional lumber size works out better in the calculation for the length. So I revisit the 3" size and work out the measurements using 1" x 3" boards.

((40 * 2.5")/12) = 8.3334 feet -- same as the 2" x 3" length which looks right.

(40 * (8' * .47 lbs)) = 150.4 pounds

This gets us down to a workable approximate weight, but we can figure this out to a closer weight. Since half the boards look like they are cut down to about 7' and the construction uses 2 boards to connect a side we change our calculation to (22 * (8' * .47 lbs)) + (20 *(7 * .47 lbs)) = 148.52 lbs. This seems very reasonable for what I am seeing and what it is reported to be used for.

Now that we have an idea of what type of board was used we can start designing.

Step 3: Rough Out Your Design

We have the basic building board size to work with and some idea of how it looks like it is put together lets make a rough design and see if this all pans out in the design.

You can use simple pencil and ruler, even a program as basic as PowerPoint or Word can give you a rough idea of what it might look like, but you will have to work in scale.

Scale - For those who don't know scale is a calculated size change that allows you to draw and design on regular sized paper and draw large things like a house. A typical size scale for drawing houses would be .25" = 1'. Which means for every quarter inch on the paper will equal 1 foot in real life. Design software lets you draw the object on the screen with the real sizes you want showing as you draw it. The scale is taken care of when it is printed based on the size of the paper and size of design. Inside the computer it doesn't matter much since you can zoom in and out, but moving it to real life needs a set scale to keep everything the same when comparing them on paper.

If you are lucky enough to have design software that will give you a vectored pattern at size then even the better because it takes care of the scale for you. 3D design is even better because you can build the entire thing in virtual then rotate it move it around and see if it looks like the sizes in the picture. Turn the angle so the design matches the angles in the photo and see if what you made matches what you seen in the photo.

The roof design is very easy. I can see there are alternating long and short boards connected together with two boards running perpendicular to the rest. So 42 rectangles with a width of 2.5 inches and lengths from 7 feet to 8 feet, alternating lengths, aligned on the bottom and two of those perpendicular to the others holding them all together. Make two, rotate to face each other and the tops should weave together. All you need now is something to hold the bottoms from sliding apart and it all falls down on you.

So we need some ends to help stabilize the two sides. The ends are a bit more difficult. I can't see the entire end piece where the door goes, and the edges of the boards are not easily seen, due to the angle, the wood grain, the image quality and size. So my first guess is going to be: What is the full width of the end? The end appears to be at the very least an isosceles triangle, having two side the same length due to how they are constructed. It is even more likely an equilateral triangle to keep things strong and the measurements the same.

I design an end with a 7 foot bottom board and two 8 foot boards crossed at 7 foot and just touching the ends of the bottom board to so the relationship of construction. I then start putting in the other boards to fill these end triangle pieces to see what is the best way to fill the space and to see how to add the door which I guessed to be about 20" wide by 40" tall.

I found that when I use a center seam pattern I end up not having to rip cut two boards to fit the door way. If I use a center board pattern the door the boards need to be rip cut to fit the size. The nearest board in the photo near the door looks to be full width as does the nearest board in the door. So it doesn't appear any rip cuts were used in the original. It is hard to see in the original photo if this is true at the center of the end wall due to the lack of detail in the photo and it being obscured by the roof line.

The build is much easier by not using the center gap than the center board layout on the end. Fewer boards are used so the cost and work is reduced. The rear end uses the same pattern, same board cuts, and no door cuts. The edge boards cannot be seen in the photo, so their placement and use are part of my experience of how to build it to hold it all together solidly. They appear on the outside in my design only to see where they go to recreate the cabin seen in the original photo.

What I would change from the original photo: Use 3 boards on the roof pieces rather than the 2 seen. I would use one at the top of each just under the ends of the 7 foot boards (and likely on the outside), one across the bottoms (on the inside), then one across the center (inside).

I have my basic plan based on what I knew about board size and applied that to reconstructing the original design, which I then thought of some ways I would build it better for me. I'm not saying my way is right but how I would build it for me.

Step 4: Try the Design

Many of you would be willing to just start building with the design I have put together so far. I myself would be willing to start the build and try it out at this point. But maybe you are building for someone else or trying to sell your design and they may need a little more. So lets give them something more to look at.

This is a small design and I am uses to working at scale and some experience in making 3D designs. I used a small free online 3D design page called TinkerCAD. Tinker works well for small items for 3D printing, so I need to work at scale for this project to get a feel that the ideas I came up with in the prior step works out.

First build your pieces:

- boards with a 1" x 3" profile, a real profile of .75" x 2.5" in lengths of 8 foot and 7 foot.

Start moving the pieces in place with a 7 foot base board, and start placing alternating 8 foot and 7 foot boards angled at 60 degrees on opposing sides adding more as you move back inline as the side would go. The 8 foot boards should cross at the top at the 7 foot line, and the 7 foot boards butting up to the 8 foot boards crossing over them.

Add the end boards using the center seam pattern moving out from the center until the end is filled in. Each board will need to be trimmed down to match the inside angle of the roof boards.

Once the end is filled use a hole shape to cut the door from the end. Build the door group the board elements so they move as one object and place the door in the opening.

The size and pattern looked enough like the original that I believe the board size is correct.

In this example I used known sizes of what could be seen in the photo to recreate the design.

Next, I will show you how to calculate dimensions from a photo.

Step 5: Calculate Dimensions From Unknown Size

In this example I will be showing how to calculate sizes from a photo with unknown dimensions from an ancient Chinese crossbow trigger system discussed on a blog. Calculating measurements from an unknown takes a little work and some basic mathematics.

First print or display the image you want to work with, and get out your ruler. Clear plastic rulers are very useful since you can see what is under it. Printed images are sometimes easier to work with as you can write on them, and set up dimension lines and angles from points to measure from.

If you are displaying it electronically you need to make sure you do not change the size or zoom of the image until your are done. Changing the display size will change the scaling factor used. Smaller items that can be printed bigger than what you think they are, will have better accuracy as you scale them down than large items that are being measured with a small ruler and scaled up. This means that a scaled up image measured to the 1/16" and that measurement is multiplied by 0.5 to get the real size which will give a measurement to the 1/32". Images that are scaled down that are measured to the 1/32" but needs to be scaled up to a foot or more will have a large variance of where that measurement actually falls. An error of 1/32" when measured can result in the real world object being off by a foot or more.

If nothing on the image or in the description of the image gives a measurement or scale of any part of what is pictured you need to make your best estimate of what you think some part might be. Pick some feature of the image and estimate what the real size would be. I am picking the rear pin through the trigger to determine the scale factor.

I displayed the image so the head of this pin is 0.75" displayed, and estimate the head to be 0.375" in real life, and the pin to be 0.25". Using these sizes the ratio to figure out the rest of the dimensions will be 0.5. So each measurement will be scaled by 0.5 for the real world size.

I set up a spread sheet to keep track of the measurements and automatically do the calculations to real world sizes. Each measurement added to the spreadsheet will be scaled by multiplying the measurement by 0.5.

Start measuring the different parts of each part and their relation to each other. In this image there are two pins that hold all the parts in a mount so the measure between those two points helps place the parts in relation to each other. The only problem with this image is there are no images of the top of the trigger system.

Make good descriptions of what is being measured and what that measurement is. Use the scaling ratio to convert them to real world sizes. Now that you have the measurements in a spread sheet it becomes easier to recalculate the scale ratio if you find a note that gives a size of the real item all the scaled sizes can be changed quickly either up or down. If you are using metric it is even easier to convert the sizes.

Step 6: Use the Measurements

Again using TinkerCAD I build the trigger system as best as I can from what is seen in the image and my measurements.

The interior is another place I had to estimate the sizes, but from my measurements the basic pattern can be made fairly quickly from the side. When it came to working on the interior I started with estimating what the width of the bolt or arrow to be used. Estimating a bolt shaft size of between 0.25" dia. and 0.375" dia. and using 0.25" for the two sides of the string catch I estimated the string block to be 0.875" wide, thus needing the small pin to be at least that long.

I decide to put 0.25" of material on either side of the string block since it is likely the widest moving piece used in this trigger system. From this I can estimate the trigger pin and falling block pin would need to be at least 1.375" long shaft and having a larger head. The falling block and trigger would be about the same width as the space estimated for the bolt (arrow), between 0.25" dia. and 0.375" dia.

Now I have a roughed out basic idea of the shapes and sizes of this ancient Chinese crossbow trigger. I can now work with the layout and final shaping of the parts and see that they all work together.

Step 7: Final Thoughts

Now I have two layouts and plans for some interesting and fun projects to make myself. The first coming from applying known sizes of objects in the image, such as dimensional lumber, to figure out the overall size and build of the project shown. After figuring out which lumber was most likely used to create it and a little evaluation of my initial thoughts to get to the final idea and making a pattern.

The second from choosing a size to assign a part in the image and converting all the measurements taken from the image by the ratio between the assign size and the measurement taken of that same part. After that it is just measuring and converting those measurements to what may be the real life sizes.

All of this gets very easy with some design programs that allow you in import the images and trace the shapes as separate objects, discard the rest, and resize it all until it gets to the size you want. You can even check that everything works together well through the movement of the pieces together. This works very well with smaller objects since less detail is lost in images.

All that from a couple images found online that had no measurements associated with them, no size references in their descriptions, and no plans to build from. I hope this ible helps those who are just learning and those who have work with their hands for years and are looking for any good tips to help make their builds easier. Thanks.