RE: Request for information - if possible

Hi,
Can someone tell me if it is possible to take a photograph of a building elevation and create a CAD drawing of the elevation from it
assuming that the lens distortion has been removed prior to using the image
any help appreciated
regards
loupou22
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I would insert the picture as a raster image and use it as a templet to draw over, then remove the image and scale the drawing to full size. To do that you will need to have a the dimension of some part of the building that can be used as the reference.
It's a long process and needs to be done carefully, with many "Display Order" "Send to back" instructions and difference coloured lines to show above the photo...
...but it is possible.
Brian.
snipped-for-privacy@nosey.com () wrote:

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Hi All
Thanks for the information, it is really useful and I will continue to look back here to see if there is any other ideas.
Fortunately I can do photogrammetric rectification, an odd skill I picked up over the years (go figure!), so I can use my leica laser to do a quick trig. to get the size of the building and the reference points to stretch the image back to a usable reference image - making sure that I have removed the lens distortion first of course - but just wanted to make sure that it was okay and possible to draw from this image for a full elevation.
Only ever done stone by stone drawings of parts of a building before now, I don't use Corel (got tired of it some years ago), but am proficient in Photoshop and Illustrator and have a passing knowledge of CAD for the purposes of Photogram. of specific angles and their removal etc...
It sounds as though, from what people are noting here, that it is possible, but that the number of references points and measurements just needs to be increased, to take account of the size of the building etc...
Would it be better to photogram. rectify a part of the building on its own and then stitch together, or just do the whole building at once? Also, what happens to the 3d parts of the building? I have only done stone by stone drawings of small areas, so never had to deal with any 3d points of a building, just 2d. What will those parts transfer like?
Its a long terrace of buildings, very dilapidated,so I am concerned that getting the correct distance from a building over the entire length may be problematic - thus giving false distance points over the entire range - but could stitch line drawings better later on in the process if multiples are used - so perhaps that is the way to go?
Again, will keep looking back, so any pointers appreciated
thanks again all
laters
loupou22
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Loupou22 - How do you do photogrammetric rectification? It sounds useful.
Dick Alvarez
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Yes, it is possible. I do it occasionally, using Windows XP Pro 2007, and AutoCAD LT 2004. I do it so seldom that I forget how every time. But here is my recollection. Start with a .jpg photograph. I don't know whether other formats will work. Right-click on the screen-listing of the .jpg photograph. Select "open with Internet Explorer". Right-click on the photograph (now in Internet Explorer). Select "Copy". Close Internet Explorer. Open an AutoCAD file. If you have not already created an empty layer (not layer 0), then do that now, and call that layer "photo" or something like that. Make that layer current. Type command "pasteclip", or "^V". The photograph appears in a box with grips. You can move or zoom or stretch the photograph with the grips (if you are set to show grips). Escape to eliminate the box with the grips. You still can use "pan" and "zoom", or you can go back to the grips if you want. Some times when I zoom, terrible things happen to the photograph image. If anybody knows why, please tell me! If you want to draw with AutoCAD on the photograph, then open a new layer, make it current, and draw. You can zoom into the photograph in order to draw very accurately, generally up to the resolution limit of the photograph. The photograph layer generally uses most of the memory in the AutoCAD file. When you finish drawing, if you do not want to show the photograph, then you can freeze the photo layer. Or you can erase the photograph, and free that memory, by right-clicking on the photograph, and selecting "Cut" or "Clear"; then purge the drawing. If you have any trouble with this procedure, contact me, and maybe we can clarify it by telephone while we both go through the procedure simultaneously. If anybody has a better way of doing this, please tell us.
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Professionally. This is the proper way to do it: Fast production. Low labor expense. High quality.
(1) Take photos as far away as you can, and at a height of as near to center as you can, and as close to staight on to the center of a side (or face) as you can (do this for each side or each face) while still having sufficient detail. This will reduce distortion due to angles of view. (2) Save a copy of each of these photos in full color. Save a copy of each of these photos in full grey scale. Save a copy of each of these photos in "2 color" black-n-white. (3) Use CorelDRAW and CorelTRACE (most older versions are even capable of this) to undo the distortion of the building. This means that the sides of a building which is photographed from the bottom up close, which looks skinny at the top and wide at the bottom, becomes the same width from to to bottom when scaled in the picture. Do this to all of the similar pictures which are in color, in greyscale, and in black-n-white, using the SAME distortion removing commands for each. Save all of these "fixed" images as bmp or jpg or whatever you prefer (and is usable). (5) Use 3dStudioMax (2.0 or any newer) to quickly create a mesh of the images as multiple boxes, while using the saved fixed images as backgrounds in the editing of the boxes. You might occationally find, by comparing the full color backgrounds and the grey scale backgrounds and the 2 color b/w backgrounds, something that you missed. (6) Map the boxes, in 3dsmax, either combined or seperate as needed, the full fixed images or parts of the fixed images. View the results, and then if necessary adjust the boxes. (7) If you need, save the 3dsmax in 3ds or dxf format for Autocad (at least version 2000) and then use Autocad to very quickly find dimensions of the building.
Other programs work, but do not produce as quick and useful a result. A lot of people hate 3dsmax because they, when they were younger, were not able to learn its full capabilities due to lazyness and/or impatience. It and autocad are the absolute best, even better than the vastly more expensive 3d programs out there.
CorelDRAW, CorelTRACE, 3DStudioMAX, AutoCad. To get good (really quick, no help need, instructor level) at these: (using them 8 hours per day and 5 days per week) CorelDRAW has about a 6 month learning curve. Writing good quality scripts for CorelDRAW is about a 6 month learning curve for the non-programmer. CorelTRACE has about a 1 week learning curve. 3DStudioMAX has at least a 13 month learning curve. 13 for a programmer, 18 for a non-programmer. AutoCad (AFTER you have learned the others) has about a 6 month learning curve.
I used to be an instructor of each of these. If you do not have a lot of time, and want to force feed yourself through the learning curve quickly (in about 1/2 the time), simply open them up one at a time in the order that I gave, read the ENTIRE help files from start to finish twice, and go through ALL of the options, and try ALL of the possible combinations, and reload sofware and operating system when necessary.
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On Oct 17, 11:39am, snipped-for-privacy@nosey.com wrote:

You didn't mention whether you were looking for 2D views/elevations of the buildings or a 3D model. I am in the business of using scanned image files to create accurate, well structured 2D CAD files. It is commonly called CAD conversion. I use Autodesk Raster Design, an Autodesk product that runs in AutoCAD (but not in LT). Raster Design has all the tools necessary to adjust the image files to correct distortion of any kind. Typically I work from B/W TIF files of the original drawings or blueprints because that way they come into Raster as a transparent image, making tracing over easier. In your case the photographs of the buildings would probably be opaque, if they are actual photographs of the building with all the background imagery included. Tracing over would be more work because every line type would have to be a color so it would show over the photograph, which would be set up so as to be in the back of the draw order. Bottom line, yes it can be done. Would it be expensive? Yes, if you don't have the software and want to buy it to do it yourself. It will also be expensive to have someone in the business do it due to the time necessray to set up the drawings and trace all the elements.
Daryl Stockton e-CAD-IT.com
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Daryl,
thanks for the reply - already noted the 2d v 3d question in a follow up tagged to the end of this discussion.
Not sure that I agree that it would take a long time, as I have already completed smaller stone by stone drawings in a relatively quick time. In fact I have drawn every stone on a bronze age burial Cairn in only 3 days from rectified photographs (which I can do) - okay, your nose and ears bleed and your eyes pop out and your head hurts like hell, but it was all completed in three days!
thanks for the information though
regards
loupou22
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I've used a photo recification program called Photoplan
http://www.theolt.com/products/pp/product.html
Found it quite useful for drawing building facade elevations, although not especially quick. Basically you trace over a picture that has been streched square so it looks more like an elevation.
There's also Sitemaster, which looks similar, although havn't used it.
http://www.graebert.co.uk/index.php?option=com_surveying_uk&ItemidV&id=Photogrammetry
Think both have free trial versions.
Hope that helps
Chris

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Thanks for the info
photoplan is indeed okay for perspective work, but at nearly 800 and a trial version that puts square artifacts over the output pictures +, if memory is right, you need a version of AutoCAD, as its a plugin, its not exactly cheap and/or simple
:-)
though I have used it with some mixed results
etc...
thanks one and all - I will see if I can do it and if not, then beg a large format with a reduced distortion lens adaptor and spot point the building - easier to stretch it out and measure that way
funny how a good full plate film camera can still sometimes work better than most modern stuff
laters
loupou22
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