[Mapnik-users] Displaying a bounding box according to kilometers instead of degrees
anisha.kaul at hitechroboticsystemz.com
Mon Apr 12 12:23:38 CEST 2010
I am able to successfully display a bounding box on the map given some latitude/longitude values.
Now I want to display the bounding box according to kilometers.
i.e. Let there be a point on the map according to some given latitude/longitude values, I want to display an area of 5 kilometers on
the map while keeping that point as center.
The method I tried is presented below:
(Below currently I have not used any center point but I have tried to display the bounding box in *meters*)
projection e ("+proj=latlong +datum=WGS84 +lat_ts=0 +lon_0=0");
double latA = 70.18722200000001;
double lonA = 20.671857388281254;
e.forward (latA, lonA);
double latB = 95.4028777;
double lonB = 35.90895391171875;
e.forward (latB, lonB);
m.zoomToBox (Envelope <double> (latA, lonA, latB, lonB));
There being no documentation w.r.t the functioning of *forward ()* function of projection class, all I could assume after reading
the *man pj_fwd* is that the *forward ()* function reads latitude and longitude values in decimal degrees, and prints the projected
cartesian values in "meters".
How should I use the forward() function to achieve above task ?
Whats wrong with the above code (The bounding box is not changing if I comment out the projection functions in the above code) ?
Kindly guide !
Hi-Tech Gears Limited, Gurgaon, India
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