Converting Photo to Orthographic Drawing [Archive]

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electrosteam

26th June 2015, 09:47 AM

electrosteam

2nd July 2015, 08:47 AM

Well, I thought that this was not a trivial question, and after 128 views without any comments, it may be harder than I thought.

It seems to me that the solution must involve an iterative approach with rough approximations, a trial development, and then to modify the approximations towards, hopefully, the correct solution.

I have some ideas that I will report on once I have proved them.
John

Mobyturns

2nd July 2015, 09:10 AM

Some of your answers will lie in researching aerial photogrammetry. However terrestrial photogrammetry will have more application to your task as it is widely used in applications such as building conservation these days. The solution is much simpler with flat building facades which at least have parallel & orthogonal planes over the types of surfaces found on machinery.

Photos are a central point perspective where scale varies continuously proportional to "depth" (distance from lens) in the photograph and point of interests offset from the "axis" of the photograph. Those relationships are well understood with aerial & terrestrial mapping and photogrammetry. Originally analytical (mechanical) stereo plotters were used with stereo pairs of image, usually with an offset or overlap of 60% forward & 25% side, to take measurements in the "stereo model." The stereo model is formed by rectifying the photo pairs first, a process of manipulating the plane of the photograph then bring them into orientation to form a stereo model.

Unfortunately it is not a trivial exercise but it can be done with well taken images and a simple stereo-scope, or a stereo-comparator if you just happen to have one lying about.

Back to your problem - a simple solution - Scale errors can be controlled in a simple image if the image coverage (area) is limited and the depth of field is not to great, so lots of small area images of components if you have access to the subject.

http://petriefied.info/Petrie_British_Stereo-Plotting_Instrument_Design_fulltext.pdf

As an aside, If you are doing this for historical machinery conservation purposes there are very modern surveying instruments that can easily scan an object producing 3D point clouds that are then modeled into 3D surfaces etc. Accuracy of a few mm or better is achievable. These instruments are used routinely in modern surveying practices but producing working drawings will not be a cheap exercise.

Skew's_Girl

2nd July 2015, 07:22 PM

Couple quick questions about the photos and camera.

Do you know how far the photographer was standing from the object?
Have you had the distortions on the camera lens mapped?
How accurate do the measurements need to be?

I ask because camera lenses have flaws. There will be minute variations in thickness and density in the lens that will distort how the object is recorded in the image and thereby affect your measurements. How close the person is to the object will cause parallax and you'll have to know the distance between the object and the photographer to compensate for distortion from nadir.

But if your measurements don't need to be very accurate, than the issues may be glossed over.

KBs PensNmore

3rd July 2015, 02:23 AM

I see the question as a bit vague, but that could be me :rolleyes:. From memory of art at school, everything meets at a point in the distance, if 2 lines appear parallel, they will meet eventually. The way I do scaling, is to enlarge the photo up to a size that is workable to get the fine details required. As the width or length is known or can be found, scaling can be worked out, ie. if it's 8' wide and you want to go to 5", I divide 96" (8'X12" = 96) X 5 =19.2. I scale the enlargement to correct full size then divide it by 19.2, which then gives me my scaled size.
Kryn

electrosteam

3rd July 2015, 10:19 AM

Thanks for all the comments.

The photo of the prime subject was taken in the 60's from an unknown height, distance and oblique view.
These are the factors that determine the projections to get the orthogonal drawing.

The only known factor is the noted length of the subject.

By using common sense and inspecting the photo, approximate values can be assessed for the height above the ground that the photo was taken, the distance to the subject, the angle of the oblique view, and that the subject is essentially a plain flat-sided box.

As the appearance of the two visible sides both taper away from the viewer one can assume, for this exercise, that the perspective view can be regarded has being arranged with a horizon line through the subject with vanishing points to the left and right.

With the assessed values and assumed arrangement, one can draw projections back that show where the subject orthogonal plan vertices are located and attempt to position an assumed rectangular plan to suit.
I suspect one must assume a subject width to get a solution, which in this particular case can be closely estimated by reference to other technical documentation.

As an aide to checking the viewing point, I think it should be possible to check that the the assumed viewing point does produce the correct tapered views to the two vanishing points.

Once the first orthogonal solution was obtained, the corresponding perspective sketch can be produced and compared to the original photo.
A visual inspection should then enable refinement of all the assessed and assumed values and the process repeated to move the solution closer to the correct one.

This has been a fascinating exercise with multiple pencil sketches on scraps of paper.
I have obtained a drawing board with a large roll of paper and will attempt to apply the approach described above.

John.

RoyG

3rd July 2015, 12:36 PM

I have searched the web for a simple description of the Descriptive Geometry projections to convert a perspective photograph into an engineering drawing (3rd angle orthographic).

There are lots of discussions on the relationships between views, how to draw in perspective with arbitrary assumptions, deep technical texts on multilayered projections and lots of software matrix conversion theory - but no simple procedure that I could find.

I think I have developed the simple drawing projections to convert an orthographic drawing into a perspective sketch, and I intend to try and work those projections backwards.

I do not need any references to software routines or fancy photo manipulation programs, just the projections that one could utilize with pencil and ruler on a drawing board.

Can anyone point me to a suitable source ?
Is anyone interested in discussing the problem ?

The particular immediate application for me is a photo of a very old electric narrow-gauge locomotive that I will like to model in 5 inch gauge.

John.

John,

I know that you said that you "do not need any references to software routines", but stay with me, as I believe that some of the techniques that are used to create a working drawing from a series of photographs using a computer drafting programme such as Sketchup, are also transferable to using a drawing board instead of a computer.

The basic process using the computer program (you substitute your drawing board), is to trace a perspective drawing over the photograph, and then convert the perspective drawing to orthographic projections or whatever projections you need. It sounds simple, but it isn't ! You soon find out how much distortion there is in the photograph when you realise that lines in the photograph that should be straight, are in fact curved in the photo.

I've done this process a few times now to create plans for reproduction antique furniture. The results are a set of outline drawings that are sufficient to start designing the construction of the reproduction item, and to produce the working drawings.

There are a few limitations that apply to using this process to get an accurate drawing. I know that you're using a very old photograph, so some of the following limitations are out of your control, but if you know about those limitations, it may help when you're doing the drawing. The most important limitations are:

The photographs need to be taken with the film plane (or digital sensor plane) as near to vertical as possible, and normally, you would record the camera height and camera's distance to a specific point on the object, to help when drawing an accurate perspective view. For example, if the photographer tilted the camera up to get the top of the loco in the photograph, then you'll also have converging verticals to deal with. The opposite errors would be present if the photographer was above the loco (i.e. on an over-bridge) tilting the camera downwards to look at the loco.
You'll get the best results if you can get photographs that are as close to orthographic views as possible. For furniture reproduction, if I am taking the photo myself, I aim to get four views (front, back, and both end views), plus close-up views of detail features.
It is easier to do if the camera lens that was used to take the photograph was a "standard" lens, that is, one that is equivalent to a 50mm lens on a full frame 35mm digital or film camera. If a wide angle or a telephoto lens is used to take the photograph, you will encounter much more perspective distortion - distance shortening with a telephoto lens, and distance expansion with a wide angle lens.
Include a measure in the photographs. When photographing furniture that I want to reproduce, I include two rulers in each photograph. The rulers are placed on the face that I'm photographing; one oriented vertically, and one oriented horizontally. They are used to accurately scale the drawing.

I've tried to use oblique photographs to produce a set of drawings, and it is much harder. It soon becomes apparent that a camera lens does not produce a true perspective drawing. One technique that you could try to gauge how much perspective error there is in your old photograph, is to use a photocopier to enlarge it to A3- black & white will do. Then sit down at the drawing board and start looking for a combination of horizon lines and vanishing points that work on that photograph. If you're lucky, there will be only a small amount of distortion that you may be able to work around.

I did one set of drawings of an antique desk. The photographs were a series of oblique views taken from a book published by a Museum in the UK. I wrote to the museum and told them I wanted to build a reproduction, and asked if they had any scaled drawings of any sort for this item. They wrote back that they didn't have any scaled drawings (and asked for a copy of mine when I'd finished them), and instead sent back a series of A3 photographs with lots of accurate measurements marked on the photographs.

That same approach might work in your case, if there is one of these locos in Museum or Collection somewhere in the world..... If not a loco exactly the same, then maybe a close cousin might provide the key detailed measurements that you'll need to start to produce accurate drawings from your photo. If you're lucky, a museum or collection may even have preserved some original manufacturer's drawings. I remember visiting the Railway Museum in York UK many years ago, and as part of the museum tour was shown their massive collection of manufacturer's drawings for most UK based engine manufacturers, and for many of the overseas subsidiaries of those UK manufacturers.

Anyway, I hope that info helps. Let us know how you get on, as producing working drawings based on photographs is a near essential process for anyone who wants to build reproductions, wither the reproductions are scale locos or furniture.

Regards,

RoyG

ian

3rd July 2015, 09:11 PM

I do not need any references to software routines or fancy photo manipulation programs, just the projections that one could utilize with pencil and ruler on a drawing board.

Can anyone point me to a suitable source ?
Is anyone interested in discussing the problem ?

The particular immediate application for me is a photo of a very old electric narrow-gauge locomotive that I will like to model in 5 inch gauge.

John.Hi John

I can't help you much with your first question.
These days very little drawing is done by hand, lots of sketches, but very few real drawings.
what I recall from when I learnt to do orthographic drawings, there was no "routines" as such to go from perspective back to orthographic. Students were expected to learn how to go from orthographic to perspective -- reverse engineering perspective into orthographic was reliant on a students "intelligence"

But your second question ...
what do you already know about the loco?
basic dimensions -- length, width, height, gauge ?
don't assume lines on the original are actually parallel ?

assuming you want to get your model as close as possible to the original, I'd be approaching the "problem" as an iterative exercise.
create a set of outline orthographic drawings
distort that object to match the perspective in the photo -- check for significant differences
adjust the drawing and try again

the process is much faster if you work with a solid 3-D computer model, but you don't want to go that route

AlexS

10th July 2015, 08:36 AM

OK, this may or may not be helpful.
About 30 years ago, National Geographic carried out an investigation using old photos, to see if Peary had really reached the North Pole. They made some assumptions about height etc., and measured shadow lengths etc. The article gave details of their calculations and methods, which could be helpful.
If you visit your local doctors surgery, you may find the magazine article and get some help.

electrosteam

10th July 2015, 09:11 AM

I have gone silent for the last week doing 'other things' but I have done some projections on paper that soon became a forest of lines, so I thought I would try the CAD as a demonstration of the method.
The multiple layers and easy erase of the CAD should make the forest controllable.

But the CAD also has a problem, I immediately ran into the absence of a command to " draw a perpendicular line from a selected point on a line".

This simple construct is the fundamental basis for the classic ruler, square and pencil on a drawing board.
I have searched and it appears to be a construct that is not commonly available.

There are numerous work-arounds, and my current favourite is to construct a rectangle along the line and out to the required distance, then add another line on top of the perpendicular leg, and erase the rectangle.

Have I missed something ?
I use DraftSight and LibreCAD.

Still happily drawing,
John.

joe greiner

10th July 2015, 04:01 PM

electrosteam

10th July 2015, 05:15 PM

Joe, and then you have to put in an offset from the original line the correct distance out, trim the perpendicular line to length and erase the offset line --- arghhhh !

I don't think a simple adjustment of properties will work because the start/end of the perpendicular line are the wrong way round.

It astounds me that this simple construct is not part of the standard CAD armory of tools.

The subject is of some interest because to draw the perspective from the orthogonal:
- draw Ray1 from the vanishing point through a selected point to the picture plane,
- draw Perpendicular1 to Ray1 at the point with a length the height of that point above/below the horizontal line,
- draw Perpendicular2 where the Ray1 meets the PP
- draw Ray2 from the VP through the end of Perpendicular1 intersecting Perpendicular2,
- trim Perpendicular2 at the intersection with Ray2,
- rotate Perpendular2 until it is perpendicular to the PP, above or below as appropriate for the selected point,
- the end of the rotated Perpendicular2 now represents the perspective view of the selected point,
- erase all the constructed lines.

Note the rotation requirement gets back to constructing a perpendicular.

The above construction simply scales the size of the viewed perspective, the size is varied by moving the picture plane closer or further away from the vanishing point.

I have swapped a forest of lines on the paper for multiple keystrokes on the CAD, not sure which is more time consuming and subject to error.

John.

ian

10th July 2015, 08:09 PM

in the drawing software I normally use -- a true vertical or horizontal line is drawn by selecting the line tool, clicking on the originating edge and holding the CTRL key while you drag your vertical or horizontal line.

Also, I can put the "forest of lines" into a separate layer

This case was drawn that way

352073

Mobyturns

10th July 2015, 09:45 PM

Yes, you have.

I know of no direct command to draw a line perpendicular from a point. In AutoCAD, I draw a line from anywhere perpendicular to the line (which may end well away from the line, but doesn't matter). Then move the new line to its target location, using its end point as object snap, and the target location as the other.

Cheers,
Joe

Copy the line you want to draw perpendicular too.

Rotate the copy 90 degrees.

Make further copies of the rotated line and paste them using object snaps (osnaps) to snap "near" or onto a "node" etc.

Commands & features will vary across CAD packages. In AutoCAD you can use the temporary tracking snaps to create virtual construction lines.

http://www.cadtutor.net/forum/showthread.php?24312-Drawing-perpendicular-lines

http://www.cadtutor.net/tutorials/autocad/object-snap.php

electrosteam

11th July 2015, 09:21 AM

Guys,
First off I apologize for dragging the topic into CAD, but, I will persevere with my initial interest in understanding the projections necessary to accomplish the task.

Ian,
I don't quite understand your method, what CAD package are you using ?

Mobyturns,
That's a brilliant suggestion, I will be trying it this morning.
I am thinking it may be possible to nominate the length as the line is drawn, so a minimum of keystrokes.

John.

ian

11th July 2015, 10:53 PM

Ian,
I don't quite understand your method, what CAD package are you using ?
John

CorelDraw is the package I most use.
it has a number of useful features, such as drag and right-click creates a copy of an object

the method I described is how you draw a straight line in Corel.
having selected the line tool the first click locates the start of the line and the second click the end.

You can set tools to snap to a grid, or object.

electrosteam

16th July 2015, 10:26 PM

Thanks Ian.

I may have made some progress, and the following text and attachment attempts to describe my method, albeit with a very simple thin rectangle.

The perspective sketch represents a hypothetical billboard viewed at an intermediate height from an oblique angle.
This view is the only input data to the solution.

1- Project billboard top and bottom until they meet and define this point as the Vanishing Point, VP.
2- Draw the Horizontal Line, HL, through the VP perpendicular to the sides. This line is also an edge view of the Picture Plane, PP, on which the perspective sketch is generated from the orthogonal drawing.
3- Nominate(ie guess!) the Observation Line perpendicular to the HL. This a commonsense judgement reflecting the view of the perspective sketch.
4- Nominate (another guess) the Observation Point, OP, on the OL.
5- Draw the Sight Lines from the OP to the Perspective Sketch at the intersection points of the HL and the sides. These sight lines will also go through the ends of the (yet unknown) plan.
6- Draw circles centered on the HL intersections with radii set to the side heights above/below the HL.
7- Draw lines from the OP tangential to the circles. These lines provide the scaling factor between the perspective sketch and the orthogonal drawing.
8- Nominate (another guess) a billboard height suitable for the proposed orthogonal drawing and use this value to draw offsets from the Sight Lines. Drop development lines from the intersections of the Scaling Lines and offsets perpendicular to the Sight Lines.
9- The intersections of the development lines with the Sight Lines denote the ends of the plan of the billboard.
10- The elevation would be projected perpendicular to the Produced Plan.

So there it is at the moment.
A bit convoluted and happy to receive criticism/comments/suggestions.
I will now try to extend the method to two planes at right angles.

If the end result is not sensible, I will have to go back and vary the nominated values.
In any real situation, some sizing data will probably be available to provide the sensibility check.

352682

John

electrosteam

20th July 2015, 11:11 AM

I have made some small steps towards the final solution.

First I have to admit to an error in the previous description.
In step 7, the Scale Line is not drawn tangential to the circle, instead, a radius is constructed perpendicular to the Sight Line (SL) to the circle and the Scale Line is drawn from the Observation Point (OP) to the end of the radius.
A very subtle difference.
The drawing itself is still OK, I just cleaned it up a bit too much for the post.

In the billboard example, if the aspect ratio Width/Height is known, you can search for the correct Observation Point because any incorrect location does not give the correct aspect ratio.
But, a lot of lines to get there.

If the object is two perpendicular planes, the correct Observation Point will produce a plan view with the edges of the planes correctly at 90 degrees, if the OP is too close, or off to one side, the construct produces a plan with the included angle >90 degrees.

Since the objects of interest to me are essentially boxes or arrangements of boxes, I feel I will soon be able to tackle the real problem.

John

electrosteam

23rd July 2015, 09:35 PM

I have made some progress, after a setback for a day or so.

My CAD is DraftSight under Windows XP on a moderately old Dell laptop, and it has worked fine for a couple of years.
That is, until the display went black, and it took me a day to realize there was still an image there, it just needed a flashlight held 'just so' to see a glimmer, apparently the backlight had failed.

A bit of searching revealed the method to select an external second monitor, and half a day to discover neither my spare LCD or CRT monitors operated DraftSight correctly.
So, get a new driver from HP Compac, no joy.

Then, (feel free to kick me over this) I uninstalled DraftSight and went to Dassault Systems to get a new copy.
But, Dassault Systems have released a new version, 2015 SP3, that is not suitable for XP, and, no sign on their site of an archive facility for old versions.
No prize for guessing that I did not have a copy of the original install.

So, search the web and get a V1R4 off soft32, install Ok, seems good, but, DraftSight reports an unstable graphics driver and that is what it looks like.
A quick link to Dell lets them interrogate my machine and they download a new graphics driver that installs Ok, and joy, everything now operates Fine.

Except - I now get an occasional warning from my protection that there is a virus trying to do something.

The subject progress is depicted in the attached drawing.
This shows two perpendicular planes in plan view, P1, with an observation point, OP1, generating the perspective sketch shown (with assumed height and an arbitrary horizon line through it).
Then, the projections are worked backwards from the perspective sketches using various observation points, OP2 to OP5, to produce the plans P2 tp P5.
The only projection lines shown are those for the sketch-to-P5 conversion, and you can see just how messy the drawing can get.
Plans P1 to P5 show different sized lengths of the plan legs, and an included angle that is not 90 degrees.

For the real problem, a non-perpendicular result indicates that the selected OP is not correct, and I hope there may be an indication of which way to move the OP to get a better result.
There is also the possibility that the elevations, when drawn, could provide some information as to which way to move the OP.

John
353496

electrosteam

24th July 2015, 11:03 AM

A small advance after some review this morning.

For a box-like object viewed at an oblique angle mid-way up the height, there are Vanishing Points on the Horizon Line to the left and to the right.

Commonsense says that a ray projected from the Observation Point parallel to the two visible sides will also recede to the same Vanishing Points.
Such rays on the Plan are lines drawn parallel to the two sides.

The attached drawing shows the previous drawing with the two parallels added.
On the left Vanishing Point the co-incidence is very good, on the right VP not so good.
But, knowing some of the difficulties producing the drawing, the error could be operator-error.

John
353568

electrosteam

26th July 2015, 10:47 AM

I did a new projection carefully and accurately and proved that the rays referred to in the previous post do meet at the vanishing points, the possible operator error is in there somewhere.

Further commonsense, and a check with Mr. Pythagoras, reveals that the Observation Point, OP, must lie on the circumference of a circle constructed with the Horizon Line from Vanishing Point Left to Vanishing Point Right as the diameter.

The circle relationship should reduce considerably the work involved when searching for the OP when converting a perspective sketch into an ortho drawing.

Thinking about it, if a photo has not been cropped, the Normal Sight Line from the OP to the Horizon Line must be in the centre of the photo.
The choice of centre would seem to be a logical first guess.

I wonder if there are any more fundamental relationships yet to be teased out of these geometric projections.

From the number of views, this subject is of some interest.
You can see from the attachment below that CAD is probably necessary for most real situations, but the projections for a simple exercise can be done on a drawing board, give it a go.

353777
John.

electrosteam

27th July 2015, 12:27 PM

Some bad news to report.
I did some exploring of the effect of moving the Observation Point along the locus of the large circle circumference.

The attached extract shows the correct normal sight line and observation point shown in blue.
I know it is correct because the perspective sketch was generated with these.

The projections were then worked backwards to get the correct two perpendicular planes in plan view with the two legs parallel with the orthogonal lines to the vanishing points.

Then I erased all the projections and shifted the OP a little to the left, as shown by the small circle, and did it all again.
The two planes are 89.4 degrees apart, showing the OP was not correct.

The next test was a little to the right.
This gave 90.000 degrees between the two planes with the planes parallel to the vanishing point orthogonal axis.
Not so good, cannot see my error.

I repeated the exercise a little further to the right, leaving all the projections visible.
Same result, perfectly (at least to 4 decimal places) perpendicular and orthogonal.

I am at a loss to explain it,
There must be something wrong with the theory, or I am making some sort of stupid mistake.
I will go back and rethink and recheck, firstly examining if greater precision on the angular measurement reveals something.

At the very least I am getting some good practice on the CAD.
353983
John

ian

27th July 2015, 11:12 PM

Hi John

I think there may be an error in your theory.

a photo contains two adjustments.

• the POV resolves to three vanishing points -- one to the right, one to the left and a third either above or below the image

• then the lens itself induces a number of "distortions" as it converts the 3-D scene onto a flat plane which may be tilted relative to the POV

I'm coming to the view that what you want to do requires a 3-D solid modelling program -- Solidworks is the only 3-D modelling program I've used.
In Solidworks the process for what you want to do would be
1. create a 3-D model of what you think the object in the photo should look like -- start with a model composed of stacked cubes, rectangles, and cylinders
2. adopt a POV that matches the POV in the photo
3. compare the Solidworks perspective image to your photo noting critical differences -- the most likely cause of critical differences between the two images will be what you though were rectilinear 3-D objects are actually tapered 3-D objects.
4. adjust the 3-D model and repeat steps 2, 3 and 4 till the critical differences between the images "vanish"

electrosteam

28th July 2015, 08:53 AM

Yes Ian, I think my expectations cannot be met with the input data of the problem I set.

Note that that the problem was restricted to a perspective sketch with verticals in the sketch, so only two vanishing points.

I put some thinking into the problem and now realize that any observation point on the circle between the vanishing points is a valid solution, unless additional data demonstrates otherwise.

A 3D model has the same difficulty, just a quicker way of reviewing the situation.
One of my ambitions is to get a 3D package running, when I get my new Windows 10 laptop.

When I have some results of my original quest available, the railway vehicle, I will submit the results for your review.
I now have to get the best possible scan of the photograph in question and attempt my first ever incorporation into a CAD package.

The discussion and method development has prompted me to put a document together describing the sequence and projections used.
It could prove useful to others and should be submitted in a week or so.

John

ian

28th July 2015, 11:00 PM

Yes Ian, I think my expectations cannot be met with the input data of the problem I set.

Note that that the problem was restricted to a perspective sketch with verticals in the sketch, so only two vanishing points.Hi John

I don't think this is strictly true.
If you look at a photo of a tall building, it typically leans into the image because of the effect of perspective. If the photo is taken at the mid height of the building the "leaning" effect is less noticeable, but still there.
I suspect that the general case is for the POV to be on teh surface of a sphere connecting the vanishing points.

In the case of your railway vehicle, it's unlikely that the camera was positioned at the mid height of the vehicle, but this would be a very very small correction compared to the big unknown of what sort of lens was used. If the lens had a field of view greater than the human eye, then the resulting image will be significantly distorted by the lens itself.

electrosteam

7th August 2015, 09:47 AM

Wow, from all the views this is a subject of some interest.
Attached is the photo that started the thread.
The descriptive document briefly mention before is currently being reviewed in draft form by one of the forum members.

Ian,
You can see that the vehicle is essentially a rectangular box viewed at mid-height from an oblique angle, hence my restriction of verticals in the perspective requiring only two vanishing points.

The only known problem with the procedure described so far is, where does one nominate the direct face-on view to be ?
Effectively, this was the camera axis when the photo was taken.
I have spent some time exploring the image, but cannot confidently nominate the axis position.

355532
John

ian

8th August 2015, 01:37 AM

Ian,
You can see that the vehicle is essentially a rectangular box viewed at mid-height from an oblique angle, hence my restriction of verticals in the perspective requiring only two vanishing points.

The only known problem with the procedure described so far is, where does one nominate the direct face-on view to be ?
Effectively, this was the camera axis when the photo was taken.
I have spent some time exploring the image, but cannot confidently nominate the axis position.

355532
JohnJohn

Ok, from the photo name, the vehicle is on the Bernia rail line at Campocologno station (I think) -- the tower and surrounding buildings are rather distinctive and the number of sort of matches Google Street view.
The vehicle looks like two units
a power / goods unit and a goods wagon
The track gauge is a 1.000 metre
I suspect the camera is positioned at about or just below the head lights
also, I wouldn't assume that the train is on a flat section of track.

CAG

16th August 2015, 10:10 PM

Look familiar? Thanks Ian.

356567

(This is South-East from St. Moritz, Switzerland, just before entering Italy.)

From your photograph, I thought the height of the camera would have been closer to the bottom of the windows rather than near the lights but this is only because I put it into a graphics program and the horizontal line I used fit there better than using the top of the lights. Seems rather high for a camera to me so go figure? The ground where the camera would have been positioned didn't look appreciably higher when looking at the above on computer. Have a look for yourself though to take it all in.

Craig

CAG

16th August 2015, 10:20 PM

The only known problem with the procedure described so far is, where does one nominate the direct face-on view to be ?
Effectively, this was the camera axis when the photo was taken.
I have spent some time exploring the image, but cannot confidently nominate the axis position.

John

As mentioned in a post further up the page, I also assume that the whole photograph is not shown. If this was the whole photograph, the centre of the image gives you the camera axis. Makes a mockery of what I just said regarding the height of the camera being about the height of the window bottoms.

356568

Also, does a 5" scale mean 5" across the rails, that is, a one-eighth scale if the gauge is 1.0m as per Ian's post? Quite a large scale (ride-on?)

Craig

DaveTTC

17th August 2015, 12:03 AM

I have not read beyond post one and two okus a saw a pic of the tram.

What i do recall from school os how to draw a scale drawing from a picture / photo. The method taught would allow you to scale in two possibly three views

Dave TTC
Turning Wood Into Art

electrosteam

17th August 2015, 08:45 AM

Craig,
The 5" gauge is the distance between the rails.
As the prototype is 1 m gauge ( 39.37 inches ) a scale of 1:8 will be used.

I already have a similar unit running, 2 x 300 W 24 V motors off 48 V from 3 x 12 V car batteries, two batteries in the loco and one in the 'bum-truck'.
It can haul 6 adults on level track.

I have applied the projections to the photo and get the Horizon Line running through the headlights.
The camera axis I used was simply in the middle of the image.
I will examine the two posted images closely to see if the axis position can be improved.

The written description of the projections is still a work in progress.

John