Help on getting dimensions from a photo

[jeffwholmes]

I am not sure that I even know how to ask my question, but hope to convey what I want to do.

I would like to take a picture of a profile and use graph paper to determine the actual size (dimensions) of a trailer. My graph paper has 4 sq. per inch, could anyone give me a bone head explanation of how to accomplish this?

My math skills are real rusty, not sure if even PB Blaster could free them.

Thanks for any help on this.

[mikeschn]

It's actually easier if you can import your photo into Turbocad and scale it to the right size... Andrew taught me this and I am forever grateful...

Prior to that what I was doing was looking at the photo, and taking a guess at either the length or height... so lets say I guessed the length was 96". Then I measured the length of the trailer in the photo and it measured 4". Then I could determine that my ratio was 24. Which I got by dividing 96 by 4.

Then I measure all the x and y points on my grid, every three inches... by 4 inches would work too...

I multiply every dimension off the photo by 24 to get the full sized dimension...

Mike...

[jeffwholmes]

Mike thanks for your reply, I have Turbo Cad LE. How do I import a jpeg?

And I know nothing about cad programs, I have played around with it without success.

Say the base length is 9'.5” how do I get the x,y you were talking about?
As I said I’m very Cad literate.

[Artificer]

First, start with the picture. You need one as close to perpendicular and centered from the actual trailer as possible. A little angle isn't terible, but its better to be square to the trailer.

Crop the photo until the edges of the photo are at the edges of the trailer (front and back). Resize the photo, so it is something like 8" or so. Make it as large as you can print, or have graph paper for. Trace the profile onto the graph paper.

You need one dimension from the photo. The longer, the better. The length of the body is good. Count how many squares that dimension covers. (example: 8' trailer body covers 32 squares)

Now you calculate the scale. For this example, 32 squares/8' = 4 squares/ft. The squares you need to draw on the wood are 12"/(4squares/ft) = 3"

Next, its a matter of counting squares, and puting the profile in the correctt square.

Failing all that... post a picture, and several people on the forum will be able, and probably willing, to convert it to a grid pattern.

[Gage]

I did it the hard way without Turbo Cad. Just took the pic I wanted and play'd with it untill I had it stretched to ten inches. I scaled it to 1 inch = 1 foot, then graft it. Once that was done, I laied out a sheet of ply and the rest is history.



Have a good day.

[mikeschn]

Mike thanks for your reply, I have Turbo Cad LE. How do I import a jpeg?

And I know nothing about cad programs, I have played around with it without success.

Say the base length is 9'.5” how do I get the x,y you were talking about?
As I said I’m very Cad literate.

TurboCAD LE may not do it... you might have to download a trial of the current turbocad pro...

then try "import->picture->from file"

then "tools->measure->distance" and get the width or length...

convert to a scale... i.e. 96"/4" = 24

plug in the scale values by right clicking on the photo, and typing in your scale values on the ribbon bar...

Mike...

[jeffwholmes]

Thanks everyone, I will try to get it. I’m on a steep learning curve though.

[angib]

It is the quality of the original photo that makes or breaks this technique, whether you do it manually or in CAD.

For anyone taking a picture to make a profile drawing, you want to:

1) Take the photo from a position that is square on to the trailer side - this is the single most important thing.

2) Take the photo from a position opposite halfway along the length of the trailer and halfway up the height of the trailer - this is not a natural height and the nearest would be to sit (not lie) on the ground. Standing up is definitely not the perfect height.

3) Take the photo from as far away as possible, using maximum zoom to get the trailer to fill the picture - this does mean you will be liable to get camera shake, so you may need a prop (see a stick nearby?) to steady the camera.

4) Take the critical measurement that 'atificer' mentioned. Better still, take two - a length (overall body side length is best) and a height (overall body side height is best).

If you want, you can then send the photo to me to add to my collection and, if there's a some decent grovelling involved (re-naming your firstborn after me - that sort of thing...), I'll even send it back to you overlaid with a grid for copying.

Andrew

[jeffwholmes]

One of the profiles I like is the Road Toad, or the Squidgit. What I don’t want to do is offend anyone by copying there design, or be looked at like a thief. I really like both designs, and really admire Rik and Dale’s design ability.
But I’m at a loss for what to do.

Thanks, for help.
Jeff

Maybe Dale would sale me his profile dimensions. I tried getting in touch with Rik with no luck.

[An Ol Timer]

I use a cad program for all my design work but I also keep a very small freeware program on my task bar that is a great quick reference tool. It is called Cool Ruler.

[mbader]

In my area Kinkos rents computer pojectors.
Hook one up to your computer and poject the picture onto your plywood sides and trace the outline.

[jeffwholmes]

mbader, thanks. I think we still have an old overhead projector at work in the education department, I had thought about doing that.

[Mitheral]

I use a cad program for all my design work but I also keep a very small freeware program on my task bar that is a great quick reference tool. It is called Cool Ruler.

That's pretty cool.