Measure Action Tool in Silverlight - Accuracy

[SlavisaCeremidzic]

Hi All,

I have couple of questions for Dominique BROUX or anyone else from development team working on ArcGIS API for Silverlight or for anyone who had to deal with the same issue. We are using Web Mercator with worldwide extent in our web based spatial solution and we want to integrate Measure Action tool in this application.

The first question:

How accurate this tool is and is there is any related documentation?

I know that if map is in projected CS, 2D Cartesian calculations are done and if the map is in geographic, geodesic-based calculations are done (based from what I read from forum posts). Also based on Dominique's note from couple of years ago that states that from version 2.2 of API for SL, the Measure Action is taken into account the Web Mercator spatial reference.

The second question:

Does this mean that even though projected CS is used (Web Mercator) that enough consideration is done in implementation of this tool to make measurement results to be as accurate as the once used for geographic CS?

And last question:

Are there any recommendation regarding estimated accuracy based on scales or geographic location that comes with this tool?

Any help would be appreciated.

Thanks

[SlavisaCeremidzic]

Interesting, there is no response on this which might mean that Redland's Silverlight development team is slimmed-down.
I'm just wondering if we should use extra caution (or even if we should use it at all) before putting this Measure Action Tool on web maps.

Hi All,

I have couple of questions for Dominique BROUX or anyone else from development team working on ArcGIS API for Silverlight or for anyone who had to deal with the same issue. We are using Web Mercator with worldwide extent in our web based spatial solution and we want to integrate Measure Action tool in this application.

The first question:

How accurate this tool is and is there is any related documentation?

I know that if map is in projected CS, 2D Cartesian calculations are done and if the map is in geographic, geodesic-based calculations are done (based from what I read from forum posts). Also based on Dominique's note from couple of years ago that states that from version 2.2 of API for SL, the Measure Action is taken into account the Web Mercator spatial reference.

The second question:

Does this mean that even though projected CS is used (Web Mercator) that enough consideration is done in implementation of this tool to make measurement results to be as accurate as the once used for geographic CS?

And last question:

Are there any recommendation regarding estimated accuracy based on scales or geographic location that comes with this tool?

Any help would be appreciated.

Thanks

[BobNichols]

I am using the measuring tools and have found them to be adequate depending on how big of an area or how long of a distance your are measuring.  I tested them by measuring known distances, for example a football field.  I found it to be pretty close, within 6 inches or so when measuring 20 yards.  It was however off by almost 3 yards when measuring 100 yards.  Granted there will be some variance depending on how good your aerial imagery is.  I would say that they should be used for simple approximations and general planning purposes only, the quick and dirty stuff.  They are certainly no substitute for a survey.

[SlavisaCeremidzic]

I am using the measuring tools and have found them to be adequate depending on how big of an area or how long of a distance your are measuring.  I tested them by measuring known distances, for example a football field.  I found it to be pretty close, within 6 inches or so when measuring 20 yards.  It was however off by almost 3 yards when measuring 100 yards.  Granted there will be some variance depending on how good your aerial imagery is.  I would say that they should be used for simple approximations and general planning purposes only, the quick and dirty stuff.  They are certainly no substitute for a survey.

Thanks Bob for your response. I have decided to do the same thing. This tool is accurate enough for orientation and approximate purposes. With declaimer information attached to it then tool should serve its purpose. I guess ArcGIS online viewer is using the same technique.