RE: pan solution

Hello

I am new to this user group and do not have any previous
experience with OpenMap so I apologize if this question
is obviously inane, but here goes:

Does Openmap have the ability to register geographic images (eg gif or jpeg)
?
By this I mean the following:

Imagine a gif map image, which has various locations specified on ite.g.
 a map of Australia with state capitals marked upon it. By "registering"
the gif I mean using some method to define a 1:1 relationship between
pixel coordinates of the gif to actual geographic locations. *see comment 1
below

Having registered (that is, explicitly defining a lat/long value for a point
on the image)
a minimum of three points (eg Melbourne, Sydney and Perth), it should then
be possible to
to interpolate within the map so as to obtain lat/long coordinates for other
pixel values
(eg the layer would "know" that the point in the centre of the image would
have lat/long
coordinates of Alice Springs,)

Having once done this I would like to be able to display this image as a
layer within
OpenMap, with the ability to pan across and zoom in/out of the image *see
comment 2.
Zooming in would magnify the image, zooming out would shrink it. This of
course would only
be useful within defined limits of relevance.

This woud be particularly useful if multiple images of different could be
layered on top
of each other and defined to be be active for particular resolutions. For
example
imagine a "fall through space" so that at as the viewer zooms in a
relevant image would be displayed (eg national map of australia)
at smaller scales, the map would zoom until the next image would be
displayed (eg state map of
new south wales). Continuing with zoom, you would then get a map image of
Sydney region,
then metropolitan sydney, then street map of a suburb) ** see comment 3

This would be a very useful feature to add in if it is not already
available.

Thanks fo any assistance in this matter

Cheers

Kurt Brinschwitz

* Comment 1:
There are a number of obvious caveats that apply here. Graphic images
are rectangular in shape, and any registered image held would be "hardwired"
to a particular
projection. If the user changes the projection within openmap once an image
has been
registered, then the 1:1 relationship defined during the initial
registration may no longer hold.
This could in theory be remedied by morphing the image so as to conform to
the projection, although
this is probably not a useful solution as the resulting image would probably
be unrecognizable.

This is not likely to be an issue for localised maps (eg street maps within
a city) but would
obviously affect larger scale images (eg depicting state or national
boundaries).

Various methods would exist for the process of registering a map. At its
simplest, a user
would just specify three non-colinear points within the map image and assign
their lat/long
values; you could then interpolate within the image for other lat/long
values. This method is fine
if the map image uses a rectangular grid coordinates, but for more
complicated projections a more
complex method would be necessary.

* Comment 2:
obviously the user would have to define zoom limits for the image, so that
they image is not
displayed if the user has zoomed too far in or out.

*Comment 3
obviously each of the maps would have to be registered, and it would be the
user's responsibility
to ascertain the accuracy of each map so that the registration process
faithfully identifies
inidivudal locations within each image correctly. Using the examples of
national, state, region, metropolitan and suburb image maps, the user would
have to be careful that
the same location (eg Sydney GPO) is identified correctly by lat/long and by
image coordinates for
each of the images.

This could be sizeable task if the user need to register several maps ...

__________________________________________________________
Dr Kurt Brinschwitz
Research Scientist
Theatre Operations Branch, Defence Science & Technology Organization

Phone: +61 2 9359 5511
Fax: +61 2 9359 5721
email: Kurt.Brinschwitz@dsto.defence.gov.au
Address: Level 5, HQAST, 14-18 Wylde St, Potts Point NSW 2011
AUSTRALIA
________________________________________________________________
"Look within - thou ART Buddha!", Zen koan, 16th century

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