+y0=0 +ellps=WGS84 +datum=WGS84 +units=m no_defs <>
tl_lon = -74.2935;
br_lat = 42.3813;
br_lon = -73.6509;
top left xy
-8270314.5893 , 5259843.0071
btm right xy
-8198780.6845 , 5189458.4882
I calculate the Centre cX,cY using the top left X,Y and Btm right X,Y...
The Size of the Image I have generated from the Map is (1031,801)...
width = absolute value of (btm right X - top left X)
height = absolute value of (btm right Y - top left Y)
Now I am trying to get the pixel x,y from the projected X,Y using this formula
px = 515.5 + (1031/width)*(X-cX);
py = 400.5 - (801/height)*(Y-cY);
This gives correct pixels if i give top left or bottom right or the centre X,Y...
But for some point inside the Image ...
the calcualted pixel X is some 2/3 pixels away from actual pixel X
the calcualted pixel Y is some 8/10 pixels away from actual pixel Y
where am I going wrong ... is the projection iam using correct for such calculations ..???
Thanks in advance.
sandeep
Il 16:04, venerdì 6 ottobre 2006, Sandeep Kumar Jakkaraju ha scritto:
> Hi
>
> a similar problem ...
>
> I want to know the img_x and img_y for a corresponding MAPLON, MAPLAT....
I believe the only way is to do some math on the server or on the client (with
_javascript_ code).
You already know the map extent and jpeg size, don't you?
You can find a lot of examples on the net, just look at the js code of one of
the many webgis clients (p.mapper, openlayers or ka-map to cite a few).
Regards.
--
Alessandro Pasotti
itOpen - "Open Solutions for the Net Age"
w3: www.itopen.it
Linux User# 167502
--
Sandeep Kumar Jakkaraju
WeBlog:
http://jakkarajus.blogspot.com
