Blurry, missing, or stuck tiles
Occasionally you may see a WMTS tile that is stuck at a different zoom level from the rest, is blurry, or missing altogether. The first step is to clear your cache.
Cache clearing instructions
ArcGIS Pro
Go to the service's Layer Properties → Cache tab and select Clear Cache. You can also clear your entire Pro cache by going to the Pro project's Options → Display and check Clear cache and selecting OK.
Browser
For web maps, you'll need to clear your browser's cache. This is usually done by pressing CtrlShiftDelete and selecting the appropriate options. For more specific instructions search "clear cache" and your browser's name.
If you're still seeing problems after clearing your cache, reach out and we'll see if we can reproduce the issue and figure out what's going on.
WMS layers not exporting
If you are using a WMS connection, you may find that the Discover layer doesn't show up when you export or print your map. This is due to a technical limitation of the WMS protocol. The only fixes are to use WMTS, export at a lower resolution, or use a local copy (for aerial imagery).
Background
In WMS, the client (ArcMap, a browser, etc) requests a map of a specific extent and resolution. The server creates a single image matching the request and returns it to the client—a 8.5" x 11" image at 100 dpi would be 850 x 1,100 pixels (just shy of one megapixel). Every time the user pans or zooms, the server creates and sends a completely new image, which consumes server processing power and bandwidth. To maintain performance for all users, WMS servers will not create and return an image if its dimensions exceed a certain size.
Applications like ArcGIS Pro and web browsers have a relatively small window and use a resolution of 96 dpi, resulting in requests that fit within the server's allowed size. However, exporting a 20" x 30" map at 300 dpi results in a 6,000 x 9,000 pixel (54 megapixel) image. This far exceeds the server's limit, and it will not return an image. ArcGIS Pro dutifully finishes exporting the map instead of raising an error, resulting in a map without the layer. You can try changing the Output Image Quality (Resample Ratio) setting to reduce the requested resolution, but the output quality will suffer.
In contrast, WMTS works by delivering a set of fixed-dimension tiles at the requested zoom level that cover the requested extent. Because the tiles are pre-rendered, all the server has to do is figure out which tiles to send and then send them—and this is sped up by the client caching previously received tiles and only requesting ones it hasn't seen yet. This allows WMTS to quickly serve up tiles for much larger and/or more detailed maps than WMS without clogging the server.
Small text or symbology in QGIS
When using the base map services in QGIS, you may experience small text and symbology when using bilinear or cubic
resampling at scales other than the normal web map scales , opens in a new tab . The resampling settings are defined in Layer Properties → Symbology → Resampling. Using bilinear or cubic resampling can look much better than the default nearest neighbor method.
This behavior is controlled by the "oversampling" value. At values greater than 1.00, the
text/symbology can appear smaller (QGIS is sending a "zoomed out" WMTS request and sampling it down to your
desired scale). At values less than 1.00, text/symbology can appear larger (it sends a "zoomed in"
request and samples it up). QGIS uses the resampling method selected in the "in" dropdown at values less than 1.00, and the "out" method at values greater than 1.00.
Printing web maps with locked down links
As explained in the licensed imagery documentation, public web maps using licensed services must use a link that is locked down to the URL of the server (usually your ArcGIS Online organization URL). However, this can cause problems with the default ArcGIS Online print services, which may send your web map to an external Print Service , opens in a new tab . The locked-down links will not authorize requests from ArcGIS Online's domain and the layer won't export/print.
To work around this issue, we developed a print proxy , opens in a new tab . The proxy accepts the same parameters as Esri's Export Web Map. When it receives a request, it replaces the locked-down quad-word with a wide open quad-word. Then it forwards the request to the Export Web Map service and passes back the response stripped of the wide open quad-words for security. You can read more about how we built print-proxy in our blog post about it. To get started, you need to get your account added to accounts.js , opens in a new tab . You can do this by submitting a pull request , opens in a new tab .