AW: [Mapserver-users] Setting the scale of the map

[Robert Fritz]

Dear Zoltan,

if you want to set the scale you have to calculate the new mapextent and
send the values to the mapserver. I tried it and it seems to work, if you
use a quadratic map.
It does not work correctly, if the map is not quadratic, obviously a error
in the my algorithm.
Maybe you can use the approach:

javascript:

--------------------------------------------------Schnipp
function scale()
{
		/*
		Formel:
		md = (width-1)/(MS_PPI*inchesPerUnits[units]);
		gd = extent.maxx-extent-minx;

		scale = gd/md;

		width = Map-Width in Pixel;
		MS_PPI = 72
		IpU = 39.3701 fur Meter

		--> for more information on this take a look
		at the mapserver-mailing list archive.
		*/



		// Wie gro? ist das Bild in Pixel?
		// map-size in pixel, if you use a constant map size you
		// take these values, otherwise:

		imgObject= parent.map.window.document.getElementById("mapimg");
            map_Width=imgObject.width;
            map_Height=imgObject.height;

	      // Wie gro? ist der Ausschnitt in GK Einheiten?
            // map-size in coordinate-units:
		// (the value is returned by the mapserver)

		 map_extent = parent.map.window.document.mapform.imgext.value;
		 //alert(map_Width+" "+map_Height+" "+map_extent);
		 map_extent_Array = map_extent.split(" ");
		 L = parseInt(map_extent_Array[0]);
		 D = parseInt(map_extent_Array[1]);
		 R = parseInt(map_extent_Array[2]);
		 T = parseInt(map_extent_Array[3]);
		 //alert("GD extentmaxx-minx" + (R-L));

		 // Bildmittelpunkt in Koordinaten
		 // calculate the center-cordinates of the map
		 C_X = (R-L)/2;
		 C_Y = (D-T)/2;
		 Center_X = (L+C_X);
		 Center_Y = (T+C_Y);
		 //alert(Center_X+" "+Center_Y);

		// Den Wert berechnen, calculate the new value:
		// window.document.form_scale.scale_value.value = the User's Input

		theValue = (map_Width) / (72 * 39.3701) *
window.document.form_scale.scale_value.value;
		//alert(theValue);
		// Den Wert dem Mittelpunkt zurechnen um neuen Extent zu erhalten
		// calculate the new Extent
		nL = Center_X - (theValue/2);
		nR = Center_X + (theValue/2);

		nD = Center_Y - (theValue/2);
		nT = Center_Y + (theValue/2);

		//alert(nL+" "+nD+" "+nR+" "+nT);

		// set the new Extent :
		parent.map.window.document.mapform.mapext.value = nL+" "+nD+" "+nR+" "+nT;
		setTool("Pan");
		.......
		parent.map.window.document.mapform.submit();

  }
--------------------------------------------------Schnapp

Robert

-----Ursprungliche Nachricht-----
Von: mapserver-users-admin at lists.gis.umn.edu
[mailto:mapserver-users-admin at lists.gis.umn.edu]Im Auftrag von Siki
Zoltan
Gesendet: Samstag, 26. Juli 2003 15:52
An: mapserver-users at lists.gis.umn.edu
Betreff: [Mapserver-users] Setting the scale of the map


Hi!
I try to create a html template where the user can set the scale of the
map. I added a textbox to the template
<input type="text" name="scale" value="[scale]">
but i failed to set extension of the generated map.

Does the mapserver use scale cgi variable as input/output or output only?
What other cgi variables can i use to set a given scale? mapext? imgext?
Any idea to work around?

Thanx
--
Zoltan Siki

Tel:+36 1 463 1146  +36 70 3199092  Fax:+36 1 463 3209
Mail: siki at agt.bme.hu
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Assistant professor at                     egyetemi adjunktus
Department of Geodesy and Surveying        Altalanos es Felsogeodezia
tanszek
Budapest University of Technology Hungary  Budapesti Muszaki Gazd. Tud.
Egyetem
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