topic Re: Overview Map Extent in ArcGIS Viewer for Flex Questions

Overview Map Extent

PhilipThompson — Wed, 24 Jul 2013 07:56:08 GMT

The documentation describes the extent which is displayed in the Overview Map as below:

"Displays the map extent zoomed out three times the main map display (until the maximum extent is reached)."

http://resources.arcgis.com/en/help/flex-viewer/concepts/index.html#/Overview_Map_widget/01m30000003r000000/

I don't have a true base map in my application. The service used by the Overview map has a upper scale threshold of 1:100,000. However once my map goes beyond a scale of 1:8100 I no longer get anything in my overview. I got a value of 8100 by making my map perfectly square. On a more rectangular map it disappears at around 1:6000.

The documentation would suggest that the overview should be showing the map at 1:24300 (8100 x 3) in which case the I should still see the map service.

If the documentation meant 3 zoom levels then it would still be visible, showing 1:64800 (8100 x 2 x 2 x 2).

Am I misreading the documentation? Is the documentation just wrong? Or is something odd with my application/map service?

Re: Overview Map Extent

GISDev1 — Wed, 24 Jul 2013 12:10:05 GMT

The documentation describes the extent which is displayed in the Overview Map as below:

"Displays the map extent zoomed out three times the main map display (until the maximum extent is reached)."

http://resources.arcgis.com/en/help/flex-viewer/concepts/index.html#/Overview_Map_widget/01m30000003r000000/

I don't have a true base map in my application. The service used by the Overview map has a upper scale threshold of 1:100,000. However once my map goes beyond a scale of 1:8100 I no longer get anything in my overview. I got a value of 8100 by making my map perfectly square. On a more rectangular map it disappears at around 1:6000.

The documentation would suggest that the overview should be showing the map at 1:24300 (8100 x 3) in which case the I should still see the map service.

If the documentation meant 3 zoom levels then it would still be visible, showing 1:64800 (8100 x 2 x 2 x 2).

Am I misreading the documentation? Is the documentation just wrong? Or is something odd with my application/map service?

In the code it looks like this:

private function updateOverviewExtentFromMap():void             {                 overviewMap.extent = map.extent.expand(3);                 overviewGraphic.geometry = map.visibleArea;                 //hide overview box if larger than overview map                 overviewGraphic.visible = overviewMap.extent.contains(overviewGraphic.geometry);             }

where the expand function is described as:
"Returns a new expanded extent. For example, a value of 1.5 will create an extent that is 50% bigger."

So, a factor of 3 would be 200% larger.

Re: Overview Map Extent

PhilipThompson — Wed, 24 Jul 2013 14:32:41 GMT

Ok, well you can't get a better answer than the code.

Not sure why I didn't look there myself. Thanks.