topic World Imagery Click to Identify - how is this done? samples? configurable? in ArcGIS JavaScript Maps SDK Questions

World Imagery Click to Identify - how is this done? samples? configurable?

HarryBowman — Mon, 30 Jul 2012 19:27:28 GMT

I can click and get metadata when the layer is added in ArcMap, and when using the Showcase Imagery Viewer.

The "view source" in the Imagery window seems to refer to a query task, but it was built with API 2.1 and I am wondering if there is a better way: the ImageServiceIdentify? No sample uses this, I think.

Is there a simple sample or a way to configure this capability in one of the online application templates, to ArcGIS Explorer Online, or to ArcGIS Explorer desktop? All I want to do it put an imagery file on the map, click, and get source and date.

[this is a cross post from the ArcGIS Online forum, but it might be a better fit here.]

Re: World Imagery Click to Identify - how is this done? samples? configurable?

StephenLead — Mon, 30 Jul 2012 22:36:22 GMT

Can you post a link to the showcase imagery viewer that you're referring to?

If it's using a query task an assumption is that there is a polygon layer representing metadata about each image (ie, they are serving the Source and Date as attributes in a polygon layer, with the polygons representing the extent of each image). Clicking on the "image" is actually running a query task against the polygon layer, and returning simple attributes.

Re: World Imagery Click to Identify - how is this done? samples? configurable?

HarryBowman — Tue, 31 Jul 2012 00:11:24 GMT

Can you post a link to the showcase imagery viewer that you're referring to?

If it's using a query task an assumption is that there is a polygon layer representing metadata about each image (ie, they are serving the Source and Date as attributes in a polygon layer, with the polygons representing the extent of each image). Clicking on the "image" is actually running a query task against the polygon layer, and returning simple attributes.

I think that is what it might be doing.
http://www.arcgis.com/showcase/

Re: World Imagery Click to Identify - how is this done? samples? configurable?

StephenLead — Tue, 31 Jul 2012 00:28:18 GMT

Hi Harry,

The code for the Identify button says:

<a id="identifyButton" class="map_button identify left" onClick="JavaScript:activateImageQuery()...

In this case, activateImageQuery is a function (not an ArcGIS command). You can find the function in the JS file at http://www.arcgis.com/showcase/javascript/main.js

This function sets up the query which will run when you click on the map:

queryImage.execute(query, dojo.hitch(this,showImageQueryFeatures, query));

When this query executes, it calls the function showImageQueryFeatures, which is sent the results of the query as a featureSet. The first feature in this set is then sent to the function showImageQueryFeature:

function showImageQueryFeature(feature) {  var attributes = { name: feature.attributes.NICE_NAME,                     nice_desc: feature.attributes.NICE_DESC,                     src_desc: feature.attributes.SRC_DESC,                     resolution: feature.attributes.SRC_RES,                     accuracy: feature.attributes.SRC_ACC,                     date: feature.attributes.SRC_DATE                 };    feature.setAttributes(attributes);    feature.setInfoTemplate(queryImageTemplate);    map.graphics.add(feature);  }

(the forum editor keeps messing up the code - the point is that it's retrieving the attributes from the feature)

So basically, there is a polygon layer (invisible) sitting on top of the imagery, and this is what is being queried when you click on the map.

Hope this helps,
Steve