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ImageToWorld - returns incorrect x/y coords

Topics: SharpMap v0.9 / v1.x
Feb 16, 2011 at 1:51 PM



I have a web system that uses the imagebutton as a map (imgMap)

I am using LO31 - Hartebeesthoek94

The roads and aerial photos all seem to load ok and are aligned, but when I click on a point it does not return the correct x/y coords.

I have the following code to define the Map

Private shMap as new SharpMap.Map

Dim size as new System.Drawing.Size(Cint(imgMap.Width.Value), Cint(imgMap.Height.Value))

shMap = InitializeMap(size, GISRdCode etc

This uses the size of the imgMap to do the following in the InitializeMap routine

Dim Map as new SharpMap.Map(Size)  and then all the layers are loaded

 When I click on a point on the Map I do the following in the imgMap_Click event

 Dim ClickPt as new SharpMap.Geometries.Point

 ClickPt = shMap.ImageToWorld(New System.Drawing.PointF(e.X,e.Y))

I display the coords of ClickPt. They are x= 2931; y=-3302249 when in fact the correct coords are x=2897; y = -3302216 (i got these from another GIS package)

I am not sure what I am doing wrong - please can someone help. I think that the way I have coded this means that the X/Y Coords of the image click are based on imgMap and not the Control Panel that it is in on the Web Page




Feb 16, 2011 at 3:45 PM

I have moved my Imagebutton right to the left and top of the page, but am still getting the wrong coords

Feb 17, 2011 at 10:07 AM
Edited Feb 17, 2011 at 10:29 AM

Hello colleen,

are you sure you have the right click point in regard to the mapimage? Maybe you need to subtract the mapimage offset.

Hth FObermaier

Feb 17, 2011 at 1:12 PM

This is really strange - I am working in using VS2010 - and was running the map in the development environment when I got the above error. I decided to install the application on the server and run it as a web app. When I run it through IE ON THE SERVER MACHINE then ImageToWorld returns the correct co-ordinates, but as soon as I run it from my machine as a web app, it returns the incorrect coords - does anyone know who to fix this - thanks

Feb 17, 2011 at 2:27 PM

OK, I've sorted this out. I had large fonts set on my screen - when I set this to nomal font then the x/y co-ordinates return correctly - not sure why this causes the problem