getting latitude and longitude from map of a city

[ChrisW67]

1. In whatever way, and using whatever method, is appropriate for the format in which the geographic data is stored. This may be as simple as loading a single image (QImage), or something vastly more involved.
2. Get the screen coordinate the user clicked on from the widget displaying the chart (maybe QWidget::mousePressEvent, maybe something else) Do some sort of mathematics to map that value to the lat/lon of the point under the cursor. This mapping will have to take into consideration the projection of the underlying chart.

[KT_HG]

Thanks Chris,
I have little knowledge about storing geographic data. Please give me some references for studding. For example if I have a offline (saved) google map of a city, then how can I load it into a QWidget?
Could you explain more about "sorting of mathematics to map that value to the lat/lon of the point under the cursor" please?

[anda_skoa]

http://inqlude.org/libraries/marble.html

Cheers,
_