arcgis-flex-apiarcgis-server
I have an application that uses a cached world basemap overlaid with more local and specific data coming from a dynamic map service. It works well for performance, but some users need to see some very detailed information in the dynamic map service.
Is there a technique to allow users to zoom in past the closest scale range of the cached service?
Bing Maps is a tiled map, so has levels of detail when zoomed in or out. I would fire a conditional statement on every extent change. Something like: event fired: Extent Change Conditional: if map style = aerial and (get level < desired): set level back at desired...
Used the Capacity Planning Tool to help compare one super heavy map service vs 4 lite map services, and the results indicate that the heavy map service is the way to go.
This may not be the right answer, and the capacity planning tool does not take into account every factor (e.g. user workflows) - let me know via comments what you think.
1 super heavy map service:
App Server CPU utilisation = 49.4%
Database Server CPU utilisation = 7.6%
Network load = 16 Mbps
Display Response Time = 0.88 secs
(Images can be seen in large by RC and open in new tab)
4 lite map services:
App Server CPU utilisation = 55.4%
Database Server CPU utilisation = 7.6%
Network load = 64 Mbps
Display Response Time = 0.32 secs each, so between 0.32 and 1.28 secs depending on web browser overheads
More logic to support the one map service approach:
All layers are in the same map service, therefore;
a. one request is sent to the server
b. one SOC process draws the map
c. one image is returned over the network
The 40 layers are spread across 4 map services (10 layers each), therefore;
a. 4 requests are sent to the server
b. 4 SOC processes draw a map
c. 4 images are returned over the network
1a and 1c will be faster and put less load on the network than 2a and 2c.
2b can use parallel processing to return a map quicker than 1b for a single user, but this will not be the case for many users. In fact, the overhead of the additional transactions being processed by the server in 2b (plus the additional network load of 2c) will see 1b scale much better as the number of users increases.
Best Answer
You can add additional levels of detail (lod's) to the configuration, which will allow you to zoom 'beyond' the available levels of the cached base map. From the Flex Viewer help - look for the tag in the 'Map content' section toward the bottom of the page : http://help.arcgis.com/en/webapps/flexviewer/help/index.html#/Main_configuration_file/01m300000018000000/
Here is a sample from a modified Flex Viewer: