Drawing scale and imported picture sizes

[DC Kelley]

I am working on an application that needs to overlay a photo of an street
intersection with a scaled map of that same intersection. The typical map
scale would be 1cm on the page to represent 1m (1:100) on the ground. I
have no idea how to control the relative size of the imported image and how
to then scale it to match my page scale needs. Ultimately I will need to be
able to translate between the image coordinate system and my page system,
but I really don't know how to start. Are there any relevant application
examples the group can point me to learn more about scaling images this way.
Regards, DC Kelley

 

[AlEdlund]

David Parker does a lot with maps (http://bvisual.spaces.live.com/), so you
might check over on his site.
al

 

[David J Parker [MVP Visio]]

And I normally defer to Chris's excellent article at
http://www.visguy.com/2007/07/13/map-distance-dimension-line/

 

[WapperDude]

Per the reference article that David Parker refers to, you need to establish
reference points on your imported picture. Since it's just an intersection,
probably there is no "drawing scale" as a guide.

What you can do...
1.) Select your imported drawing and 1st protect its aspect ratio.
2.) Then, zoom in, say, to the intersection to get enhanced resolution.
3.) Add to two connection points, one on each side of the intersection
4.) Add a measurement shape to these points. This allows you to monitor
the street width as you resize the drawing.
5.) Change the drawing size until the street width matches your scaled map
dimensions. This ought to provide sufficent accuracy.


HTH
Wapperdude

 

[DC Kelley]

Thats quite a read, will take a break and dig through it. It looks like the
project he describe has a ton of other off-topic content (but still
interesting) but perhaps in there somehware is how he realtes the phyical
map to a real scale system. Offhand I dont see that anywhere, but will keep
looknig.
DC Kelley

 

[DC Kelley]

I am begining to see how the solution can work, many thanks for all the
tips. If I can get the map "nailed" to my scale, I feel that I can tweak
it into a known precise position and then register it by some lank marks in
the view that can become the connection points.



In this rather unique case, the map is driving the objects to be captured,
not the other way around (as in the example given). So I want to lay out
the map image on a blank page to be as large as practical, register its
size/position with lat-long system (and set the Visio scale), then overlay
my map objects and finally (once the model is built) extract their position
in the Visio scale system and then translate them back to Lat-long or
express the points as as centimeter offsets from some known "anchor" points.



In this specific case the lat-long is expressed to 1/10,000,000 of a degree,
which in much of North America is about a 1cm each way, while the "local"
measured ground truth (the objects on the Visio map) is always expressed to
be in 1cm units of LSB. So I will try and register this image to reflect a
scaled X and Y value that reflects the local ellipsoid at that location
(nasty math, but better then doing a multi dimensional "mesh" of many points
like a cartographer would do). Throw in the fact that north is not always
where you think its (so we have some rotation) Off I go....

DC Kelley