topic Re: Unable to add two Web Mercator tiled map services w/ slightly different spatial r in ArcGIS JavaScript Maps SDK Questions

Unable to add two Web Mercator tiled map services w/ slightly different spatial refs

CharlesGeiger — Thu, 29 Aug 2013 01:19:36 GMT

I created a tiled map service (http://mapmaker.millersville.edu/ArcGIS/rest/services/PAoutline/MapServer) in order to create a map better suited to local zoom levels (lods). I hoped to be able to add a ArcGIS Online tiled service (http://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer) after my service loads so that my service determines the lods, but the AGO service shows its better graphics. The AGO map service will not draw. Is it because you can't overlay two services with different lods, or is it because my spatial reference (102113) is slightly different than the AGO map service (102100)? (or is it something else altogether?)

Re: Unable to add two Web Mercator tiled map services w/ slightly different spatial r

TrevorHavelka — Thu, 29 Aug 2013 10:43:11 GMT

I know in the past when using ArcGIS Online services as basemap it was best practice to use the same LOD's and coordinate system of the basemap. So you might want to start by changing your coordinate system to WGS 1984 Web Mercator (Auxiliary Sphere) and using the same LOD's as the basemap. Check out the pages below.

http://help.arcgis.com/en/arcgisserver/10.0/help/arcgis_server_dotnet_help/index.html#/Designing_a_map_to_overlay_ArcGIS_Online_services_Google_Maps_and_Bing_Maps/009300001571000000/

http://help.arcgis.com/en/arcgisserver/10.0/help/arcgis_server_dotnet_help/index.html#/Tips_and_best_practices_for_map_caches/009300000079000000/

Re: Unable to add two Web Mercator tiled map services w/ slightly different spatial r

JeffJacobson — Thu, 29 Aug 2013 15:37:30 GMT

As far as I know tiled map services cannot be reprojected on-the-fly like a dynamic map service, so the spatial reference system of all tiled layers much match. The LODs should match too, but you can omit some of the levels that Esri uses for their map services, since you most likely do not need to show the entire world.

Re: Unable to add two Web Mercator tiled map services w/ slightly different spatial r

CharlesGeiger — Thu, 29 Aug 2013 23:49:20 GMT

Thanks to both of you. The links don't precisely answer my question, but it is clear that I haven't followed "best practices." Unless I hear otherwise, it looks like I will have to create entire cached basemap services of my own in order to best represent the state-to-local LODs needed for my project.

Re: Unable to add two Web Mercator tiled map services w/ slightly different spatial r

TrevorHavelka — Fri, 30 Aug 2013 01:10:12 GMT

How close in do you need to get? The highest scale on the ArcGIS Online is 1128, and at that point your at about a couple blocks level of detail. We have a few applications that go down to 564 and 282. When a user goes that far down into detail they just lose the basemap, but are still able to view our map services.

I noticed the highest scale on your map service was 2500. So it could still be feasible for you to use the ArcGIS Online basemaps, you would just need to use WGS 1984 Web Mercator (Auxiliary Sphere).

Re: Unable to add two Web Mercator tiled map services w/ slightly different spatial r

CharlesGeiger — Fri, 30 Aug 2013 23:40:19 GMT

Sorry for infrequent posts. It's not the range of LODs that's the issue for me. I want to default to a map that fits Pennsylvania well and then have 8-10 LODs down to local level (my current smallest scale, 1:5,000,000 isn't right yet, but close; my current largest scale, 1:2,500 is about right). With the standard LODs, the largest one that shows all of Pennsylvania makes the state too small, and the next larger scale LOD cuts off too much. I'm sure they did a lot of research before settling on their zoom levels, and found the best all-around solutions, but they just don't fit my needs.

Maybe Esri could come up with a few alternative LOD sets?