RE: [OpenMap Users] Lan Lon of upper left corner

See my reply under each question, and the links at the bottom have all the code you need from web page to servlet and back.
 
Martin

        -----Original Message-----
        From: h0119153@hkusua.hku.hk [mailto:h0119153@hkusua.hku.hk]
        Sent: Tue 3/9/2004 6:35 PM
        To: openmap-users@bbn.com
        Cc:
        Subject: [OpenMap Users] Lan Lon of upper left corner
        
        

        Hi, I am trying to display SHAPE map in a servlet with openmap.
        Here is my question:
        
        1) I would like to know the lan and lon of the location in the map image when a
        user clicks his mouse on the map, how can I do this?

>>Get the x, y mouse position from either http or javascript and pass to the servlet.
        
        2) Actually, I know that I can get the mouse position on the image by http, but
        how can I translate the position of mouse on the image to the actual lan and
        lon?

>> create a Projection class passing the width, height (in pixels) of your map, the center lat/lon of the map and the name of the desired projection (like "LLXY"- you may need the type id like 2 or 3).

>>Use the projections inverse(x, y) and forward(lat, lon) methods to switch back and forth between lat/lon and x,y.

        
        I think I know the mathematics to calculate the real lat and lon provided that I
        know the upper left corn's lan and lon. How can I get those 2 values?

>> use Projection.forward(lat, lon) and Projection.inverse(x,y)
        
        3) Also, I am using MapRequesHandler to produce the map upon request. How can I
        add a layer which shows the .dbf content of the map?

>> see my postings for all the code you need....

        http://openmap.bbn.com/mailArchives/openmap-users/2003-05/1552.html

        http://openmap.bbn.com/mailArchives/openmap-users/2003-05/1553.html

        http://openmap.bbn.com/mailArchives/openmap-users/2003-05/1551.html

        
        
        Thank you for your kind attention and help!
        
        Steve
        
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