Honestly I'm a bit confused with your current scale description. I have some suggestions though.
It's easier to do all the calculations in the map coordinates (aka projected coordinates) and convert to screen coordinates only before actual drawing with AxMap.ProjToPixel. If your map units are meters it is very easy, if they are degrees it may be a bit more complicated. For such application I'd suggest to use meters, i.e. coordinate systems like Google Mercator or appropriate UTM zone.
To get lon/lat from screen coordinates you need AxMap.PixelToDegrees. There are more functions for coordinate conversion described there. You should use them rather than doing your on calculations with AxMap.CurrentScale.
Have you checked these examples: example1, example2? They are similar to your task.
Hope it helps,
Sergei
It's easier to do all the calculations in the map coordinates (aka projected coordinates) and convert to screen coordinates only before actual drawing with AxMap.ProjToPixel. If your map units are meters it is very easy, if they are degrees it may be a bit more complicated. For such application I'd suggest to use meters, i.e. coordinate systems like Google Mercator or appropriate UTM zone.
To get lon/lat from screen coordinates you need AxMap.PixelToDegrees. There are more functions for coordinate conversion described there. You should use them rather than doing your on calculations with AxMap.CurrentScale.
Have you checked these examples: example1, example2? They are similar to your task.
Hope it helps,
Sergei
