How to automatically superimpose/align an autocad drawing onto a photograph

[rj2163]

Sorry for the long post….

 

A friend was in a fender bender car accident. I decided to try to do some accident re-creation to try to help out my friend but also as an excuse to learn a little about some different software including autocad and some photogrammetry software.

 

I took some pictures of the scene (cars and most of debris were gone) and then later took some measurements and recreated the roads and intersection in autocad 2008.

 

To make a long story short I’d like to be able to superimpose the autocad drawing onto the photographs to, among other things, show on the photographs where the centre line of the road is.

 

The accident occurred on a country road and there was no painted centre line. The section of road before the “T” intersection is strangely shaped. So I decided to try to determine the centre line by doing some physical measurements but also tried to estimate it in autocad based on the drawing roadway edges.

 

So I have an autocad drawing with an approximate calculated centre line and I’d like to superimpose that centre line into the photographs.

 

There were some markings on the road that appear in the photographs that I measured and plotted in the autocad drawing. I’m wondering if there is a way in autocad, or some other software, to simply click/identify the marks in the photo and in the autocad drawing and have the software automatically orient and align the drawing onto the photo. (example photo and autocad drawing attached)

 

Thanks for any advice.

 

rj

[ReMark]

None that I know it but the technology has changed dramatically. Now accident investigation teams use high-tech surveying equipment, 3D imaging, and GPS to reconstruct all the necessary elements. Back when I worked for a municipality I did drawings for our local police department for accident investigation (usually it was because someone got killed or seriously injured). While the police photographed everything with a 35mm camera, our survey team located the curb, sidewalks, poles, guard rails, and anything else that didn't move for a distance of 200 feet in all four directions. Then we assisted the police with measuring the length of any skid marks and located those as well. It was pretty intensive. We could be at one sight for a good portion of the day. Then we took all the info back to the office and drew it all out on mylar in ink!

[JD Mather]

Align and scale with reference might be of use to you. (after inserting your image). But keep in mind that you have perspective and parallax error in your photo.

[cedwards]

rj2163 if you could attach the dwg of the site along with the dimension you have of the physical evidence there is something I can try. I don't know if it will work but it would be to difficult to explain without testing it.

[BIGAL]

Try "Align" just pick two points and "y" to scale

[rj2163]

rj2163 if you could attach the dwg of the site along with the dimension you have of the physical evidence there is something I can try. I don't know if it will work but it would be to difficult to explain without testing it.

 

cedwards - see attached drawing and also another picture of the accident scene taken at a later time with some extra road markings.

 

I'll try a couple of the other suggestions.

 

I'm getting the impression this isn't a simple thing to do.

 

Question 1: is there a way to fix the photograph, as a background image or something, in autocad so it is fixed in the autocad window and doesn't move when I try to move around the drawing layers to try to manually line up points in the drawing to points in the photo. If I import the photo as a layer of the drawing, this doesn't work because if I tilt the drawing using orbit, for example, the photo is also tilted. I need the photo to stay fixed in space then be able to move the drawing around, tilt and rotate it etc. Is there a way to unlink a layer from the other layers so it will not move when the other layers move?

 

I didn't see a way to do this in Autocad so for a cheat I downloaded a small program called Glass2k which allows you to make an application window transparent. So I put the photo on my desktop in a photography program, then put the Autocad window over that and made the Autocad window semi-transparent so I could see the photo below, then used zoom and orbit to zoom, rotate, tilt etc the drawing to try to line it up with points in the photo. It's not working very well.

 

I think I need to try to set the autocad view perspective from the point where the camera would have been. I have many pictures from slightly different positions so I should be able to use some photogrammetry software like Photomodeler or Imagemodeler. I believe they calculate the position of the camera in 3d for each photo. (I know the height and the camera settings so all I need is the x,y postion).

 

Question 2: I really haven't looked into it yet but is there a way to set the perspective/view in autocad to be seen from a specific x,y,z point to simulate the view from my camera? I'm wondering if the Camera tool could do this. note- I also know the other camera info like focal length for the photo's.

 

again, thanks for any direction/advice.

 

rj

Accident - subset.dwg

[rj2163]

.... along with the dimension you have of the physical evidence.....

 

The drawing is 1:1 scale and all measurements are in inches. the road measurements are pretty accurate - most are probably within a couple inches of the true location. So measureing off the drawing the distance from B-C is about 119in, C-D=129in, B-D= 217in etc. a

 

Measurements at the line marks on the road were taken at the middle point of the line and measurments to road marks B,C,D etc were taken at the geometric centre of the mark, hole, gouge etc.

 

All plotted points were produced by taking at least two measurements from fixed objects (road signs etc) then plotting a circle centred at the reference point with the measured radius and plotting the intersection of the two circles. So for example, in the first photo above shows B,C,D with the 60 speed sign in the background. the sign was a reference point for one measurement to each of those marks. The distance from the 60 sign to B,C,D is 676in, 781in and 873 in respectively. (Example attached - point C to 60 speed sign) BTW the 60 sign is 95 in. high.

 

Actually I just fixed the end of a 100ft tape to the reference point and ran around to each point of interest, marked the point and labeled it with chalk, and photographed the measurement on the tape and then when I was home just got the measurements off the photos, so it all went pretty fast. fortunately it wasn't a busy road:lol: I think my methodology was ok and the results were pretty accurate.

 

cheers

rj

[Coosbaylumber]

I am out California way, but we had our drawing tossed out of court three eyars ago. We represented an attorney that was dealing with an offset (partley completed) roadway. Reason:

 

Seems in California the center of the roadway or painted line is not exactly down the center of the right-of-way. It is half way alright, but then too that painted line can wander around. Long as it is between the two R-o-W lines who cares.

 

The courts need to know as to "Exactly" where the centerline of the road is at in relation to the painted line or edge of pavement. It all may fit within the deeded right-of-way but that is not exact enough for them.

 

 

Wm.