Hi there,
I have a basemap problem/question where I'm not quite sure where to put or how to solve it properly.
Our organization wants to provide a nice, performant satellite-image basemap. So far, we have our area of interest (AOI) covered in high-resolution imagery (0.08m cell size) where we provide a basemap with a cached image service behind it — cached down to approximately scale 1:140. This will come with some cache size, but images are of good quality and still performant.
Now, requirements have grown — we need the surrounding area covered with the basemap as well. However, it's more for "orientation" purposes since it's not our actual AOI. Caching to scale 1:1000 for that "surrounding" area would be sufficient. Caching the whole area to 1:140 would make the file size explode. Caching everything at 1:1000 would lead to bad image quality for our AOI.
What would be a good approach?
- Is it possible to achieve that with ONE cache? (e.g., cache one mosaic dataset in different AOIs to different LODs)?
What we've done so far:
- Cached a second service (MapService) based on "lower-resolution but bigger area" imagery.
- Overlayed the AOI with a white polygon. Cache format = "mixed" so white tiles will result in transparent PNG tiles—a Cache with a hole of transparent PNGs so we don't cover the AOI.
(Follow-up question: would it make a difference if we don't overlay a white polygon but actually clip the AOI in the lower-resolution imagery?) - Combined/overlayed both services in the web map/basemap.
It works; you can even zoom in the surrounding area to 1:140 (overzoom on the base of the 1:1000 tile); the AOI will still deliver high-res tiles till 1:140. But I have a feeling there could be better options. Right now, we always request 2 services and load 2 tiles where actually only 1 is needed (1 transparent white tile and one image-service tile).
Any thoughts, inputs, suggestions welcome 🙂
