topic Re: Getting Cached service scales in ArcGIS API for Silverlight Questions

Getting Cached service scales

egismazeika — Fri, 05 Nov 2010 13:42:37 GMT

Hi,
I have an issue while calculating the scale when using cached map services. Let???s compare 2 LODs of different services:
Resolution: 1,32291931250529
Scale: 5000

Resolution: 0,423334180001693
Scale: 5000

The trick is DPI. The first has default value of 96 while the second is 300 DPI!
So how can I calculate the cached service scales correctly?

Btw, LOD in js and flex APIs has a scale property. Why is it still missing in Silverlight?

Re: Getting Cached service scales

JenniferNery — Fri, 05 Nov 2010 19:08:53 GMT

Have you looked at this documentation? http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.Map.html

You are right that LOD only exposes Resolution but Scale can also be calculated similar to how Map Scale is calculated:

Map scale = 1 : (ScreenRes pixels/inch * 39.37 inches/meter * (Map.Resolution * conversionFactorToMeters))

Re: Getting Cached service scales

egismazeika — Mon, 08 Nov 2010 05:37:22 GMT

Thank you Jennifer for reply. I have looked very carefully at the Map topic and I find it doesn't answer my question.
My issue has nothing to do with Map or screen resolution. No matter what my screen is I need to get the actual cached scales.

Getting DPI value from TiledMapServiceLayer would be enough, but this property is missing too.

Re: Getting Cached service scales

JenniferNery — Mon, 08 Nov 2010 15:50:21 GMT

Oh I sent this link just as a guideline how you can calculate scale based on resolution and DPI, since LOD includes Resolution and your DPI varies, you can use the same formula to calculate the scale.