Wie man am besten mit großen Feature-Layern umgeht

Anonymous User

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Ich arbeite derzeit daran, Daten aus einem riesigen Trail-Feature-Layer zu erhalten, um sie in einer iOS-App zu kartieren. Um die einzelnen Trails in verschiedenen Farben anzuzeigen, dachte ich daran, die #iOS SDK-Filterfunktionen zu verwenden, um die Daten für jeden Trail zu filtern und die gefilterten Trail-Daten als einen anderen Feature-Layer darzustellen. Der Trail-Layer ist riesig, daher sehe ich, dass es der iOS-App eine Sekunde dauert, die Daten anzuzeigen. Wie kann ich diese Filterarbeit remote durchführen? Kann ich neue Feature-Layer auf arcgis aus anderen Layern remote erstellen? Kann das in einer #ASP.NET Core-Webapp gemacht werden? Und allgemein, was ist der beste Weg, um mit großen Datensätzen in mobilen Apps umzugehen.<\/P><\/BODY><\/HTML>

Nicholas-Furness

Hi.

There appear to be a lot of questions here, only some of which are relevant to the Runtime SDK for iOS. But I'll try to provide some guidance…

Firstly, can you explain what you mean by the "iOS SDK filter functions"? Are you referring to definitionExpression?

Typically, you might draw a set of data in different colors by using an AGSUniqueValueRenderer, but that might only work if you are not displaying a huge number of trails at a time. See this sample.

Which leads to my second question. How are you displaying these trails? Will you zoom out to display hundreds of trails at a national level, or do you focus in on specific trails or areas with just a small set of trails visible at any one time?

In the latter case (i.e. you have a set of trails that you know you will be working with), you could set the AGSServiceFeatureTable's featureRequestMode to manualCache. You would then populate the local in-memory AGSServiceFeatureTable using populateFromServiceWithParameters() and set an appropriate whereClause on the AGSQueryParameters. This will make the network request once, and then display the features from memory. As you zoom and pan around, your app won't make network requests to refresh or reload the data. Other featureRequestModes might end up displaying from memory, but features are not aggressively cached so panning and zooming is likely to result in repeat requests (see the bufferFactor property for some control). This way, you have complete control over when the features are retrieved from the service.

Setting the featureRequestMode to manualCache and calling populate with a whereClause is fundamentally very similar to using definitionExpression with the default featureRequestMode, except that you have total control over how long features are cached locally and when network requests are made.

As for your other questions:

• I'm not sure what you mean by "ASP.Net Core webapp".
• You can create Feature Layer Views of a hosted feature service. I do not know how you would create and manage those remotely and it doesn't sound like it would solve your issue.
• The best way to deal with large data sets depends on a lot of variables to do with the data - these considerations will have an impact on how you might publish your data and how you might access it (e.g. the populate approach above):
  • Will you need to see it all at once when zoomed out? If so, you could publish the feature layer to a tiled image service and display the tiles when zoomed out.
  • Will you be editing it? If not, you could publish a separate generalized layer for use when zoomed out.
  • How reliable is your network connection? If it's slow or variable, you could consider the populate approach above or you might consider generating a Mobile Map Package with ArcGIS Pro and using that.

Hope some of this helps, but I'd need to understand more about what you're trying to achieve.