Zoom to scale

GregoryDillon — Mon, 28 Nov 2011 18:17:36 GMT

I'm not sure how to change the math for the example in http://forums.esri.com/Thread.asp?c=213&f=2455&t=285205 for NM State Plane (2903) and Units = ersiFeet. Specifically what do I use instead of 39.37 (inches per meter)? Should this be 12 (inches per foot)? Also what should use instead of mapunitInMeters (see snippit below)?

private void zoomToScaleCombo_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (MyMap == null) return;
double dpi = 96; //Set to resolution of your screen
double scale = double.Parse((e.AddedItems[0] as ComboBoxItem).Tag.ToString());
double mapunitInMeters = 111319.5; //size of one degree at Equator. Change if you are using a projection with a different unit than degrees
double newRes = scale / (dpi * 39.37 * mapunitInMeters);
MyMap.ZoomToResolution(newRes);
}

Would this logic be (12 inch = 1 foot and since the mapunit is in feet this value would be 1)?

double newRes = scale / (dpi * 12 * 1);

or more simply

double newRes = scale / (dpi * 12);

Re: Zoom to scale

DominiqueBroux — Tue, 29 Nov 2011 11:02:53 GMT

Not sure what is the question, but double newRes = scale / (dpi * 12); looks good to me.

Re: Zoom to scale

GregoryDillon — Tue, 29 Nov 2011 16:02:44 GMT

I just wanted to make sure I had the formula right for my projection (NM State Plane) and Feet based units. I guess the project really doesn't matter as long as the units are in feet.

You told me what I need to know.

Thanks.

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