topic Re: Cache WMS service locally on device in ArcGIS Runtime SDK for iOS Questions

Cache WMS service locally on device

ThomasSvitil — Thu, 06 Nov 2014 13:02:52 GMT

Hi everyone.

Is it possible to cache WMS services locally and permanently on a iOS device? The map data is too big to store the whole map locally.

Or is this only possible with WMTS services?

Thanks for your help!

Re: Cache WMS service locally on device

KristofferStenersen — Thu, 06 Nov 2014 14:19:19 GMT

One possible strategy is to use some well known tiling-scheme to build up a cache.

Then, download all required tiles for an area of interest onto the device - according to this scheme.

Add a tiled map service layer, consuming these tiles from local storage.

Re: Cache WMS service locally on device

KristofferStenersen — Tue, 18 Nov 2014 07:47:08 GMT

Hey Thomas Svitil Any luck on this topic? I do have a fair amount of experience on this subject and I´d be happy to detail a bit more on what we´ve been doing in our projects.

Re: Cache WMS service locally on device

ThomasSvitil — Tue, 18 Nov 2014 10:47:22 GMT

Hi Kristoffer Stenersen‌.

Thanks for your reply!

Basically i find your proposal interesting and it is definitely pointing in the right direction.

The problem is that i am only able to consume the given service (in this case WMS). I have no access to the server and the data and therefore i think it is not possible for me to build up a tiling-scheme to build up a cache. Up to this date i did not find any possibility to directly cache WMS services without additional processing. So as far as i know i have to give up on the idea or get the host of the data to convert it into WMTS (or at least to generate a tiling-scheme for the cache) . I hope my assumptions are right - please correct me if i am wrong. Thanks for your reply!

Re: Cache WMS service locally on device

KristofferStenersen — Tue, 18 Nov 2014 11:32:02 GMT

You don´t need the server in order to cache the data - the clients may do this for you.

A tile can be built from a regular request to the WMS-service. All you need to know is the extent of the tile. This you can calculate from some well-known tiling scheme.

So, for an area of interest, calculate all the tiles/extends you´d like to prepare for offline, and download them all, and save them to the device in some nice z/y/x pattern so that it´s easy to fetch them later.

Then, build a tiled layer using the same well-known tiling scheme. When this tiled layer requests data from the area of interest, return the tiles already stored from disk.

Re: Cache WMS service locally on device

ThomasSvitil — Mon, 24 Nov 2014 11:00:26 GMT

Hi Kristoffer Stenersen‌.

Thank you very much for helping me out on this!

Do you have a link to useful resources about this topic? (calculating a well known tiling scheme and using it with arcgis.)

Have a nice one.

Re: Cache WMS service locally on device

KristofferStenersen — Wed, 26 Nov 2014 07:42:45 GMT

Hi Thomas, there are some implementations out there doing similar stuff, for example the GeoWebCache. But I´d start at looking at the Tile Info section of an ESRI tiled map service layer definition, or the GetCapabilities´ TileMatrixSet for a WMTS service. It describes the tiling scheme for the service.