I use the map images generated by http://maps.google.com/mapdata?
and have been using them in an executable application on my computer.
I have no need for using them on a web site or web server or any type
of
internet based setup. And I must emphasize "no need" to avoid any
confusion. The legal aspects of it are no different than if a person
were to browse to that url -> "http://maps.google.com/mapdata?";
with a browser. So therefore its legal otherwise Google wouldn't allow
access to that url even by browsers and therefore that url would not
exist. So I can use it. So now this brings me to my questions.
I have been researching the concepts dealing with this field and
understand what geospatial data is and what the WGS84 coordinate
system
and Mercator projection is for.
I have a need to find the latitude and longitude of the points under
the
mouse cursor when the mouse is over the image. (of course the image
was
brought up already knowing a lat/lon location, but I need to know how
to find
lat/lon for locations around that center point)
I have no need to understand what window,form,document,html div tags
and their client coordinates
or anything related to dealing with M$Windows coordinate systems of
graphic device context
interfaces or any web browsing software's object DC interfaces.
That's what MSDN is for. And I am more knowledged about that
than geodesy or cartography. Plus the coordinates systems that the OS
uses are unrelated to
the geographical data or geographical coordinate systems.
So let's pretend we are doing a fullscreen display of a map. 0,0 is
the left,top of screen.
And width is horizontal screen resolution. And height is vertical
screen resolution.
Just to make things simpler.
Of course this screen can be any resolution.
Which brings me to another thing I noticed, the maps returned can be
specified in any resolution with w= or h= , width= or height=
somewhat with restrictions. 600x400 is one I came across and I'm sure
a square can be made.
But aren't these done in 256x256 tiles??? And aren't those dimensions
necessary to be able to determine locations due to the
transformations???
I have a need to know how to convert from the integer pixel coordinate
locations to that particular
maps' decimal coordinates, that is if it's derived from Mercator
projection with the
implementation of UTM or WGS84.
{preferably in plain vanilla flavor, also I'm familiar with the old
Benoit Mandelbrot method of converting screen to cartesian
coordinates...
xres,yres,xmax,xmin,ymax,ymin,deltax=(xmax-xmin)/xres,deltay=(ymax-
ymin)/yres,x=xmin+column*deltax,y=ymax-row*deltay}
(Understand that I'm quite literate on viewing systems and 3D,
especially PHIGS, OpenGL, lefthand coordinate systems and righthand
coordinate systems. So matrix operations are no stranger to me.)
http://cfis.savagexi.com/2006/06/30/mouse-coordinates-to-lat-long
I have read what would be needed to accomplish this,
"So back to the problem at hand. To get from a lat/long value to a
pixel value requires a series of transformations:
1. Geodetic CS -> World CS (projection)
2. World CS -> View CS (affine) "
And this is the opposite of what I want to do. so I need to do...
1) View CS(affine) -> World CS
2) World CS (projection) -> Geodetic CS
Is that correct?
However I am still trying to determine if all that is necessary,
because I had read somewhere you
can determine the lat/lon using a center point, an azimuth and knowing
the distance between latitudes.
So what are the designations of the zoom levels (1-10) or (1-9)???
Or better yet, what are the corresponding heights or azimuths for
those zoom levels if we can do that?
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