What is the spatial ref of an AGOL web map extent?

[ChristopherMugdan]

Hi,

I have created a web map and the spatial reference in the web map data when I request the specific item is (presumably based on the base layer spatial reference?):

    "spatialReference": {
        "wkid": 102100,
        "latestWkid": 3857
    }

but the extent in the web map content item is:

        "extent": [[105.533276992,
        -43.6430919145],
        [159.105442464,
        -9.23004701800001]]

What is the spatial reference of the extent? Is it EPSG:4326 and if so is this always the case for web maps? I could not find a definitive reference for this.

Cheers,
Chris Mugdan

[Anonymous User]

It's Web Mercator Auxiliary Sphere. That is the default spatial reference in ArcGIS Online. Depending on how you are publishing you could use another spatial reference. 

How do you publish your data?

[ChristopherMugdan]

Hi Katie,

Thanks for the reply. I am fine with the Web Map being EPSG:3857 but I was wondering what the extent CRS is in the content response json as per the bold json snippet below. I could not find anywhere that says what it is. I assume EPSG:4326, but I need to know definitively.

"extent": [[105.533276992,
        -43.6430919145],
        [159.105442464,
        -9.23004701800001]]

Cheers,
Chris

[ChristopherMugdan]

Also, how do I find what units the web map is in? If the web map is in EPSG:3857 it will be metres I presume, but is there a way of getting that information as one can do when interrogating a map service in ArcGIS Server? I have not found it in the web map item (from content) nor the web map data (from the web map data request.)

Cheers,

Chris

[Anonymous User]

I think I am confused by what you mean when you say "extent CRS is in the content response json". I have to be honest and say I do not know wha that means. 

For a hosted service you can see the information about extent and spatial reference in the rest endpoint:

https://services.arcgis.com/Wl7Y1m92PbjtJs5n/arcgis/rest/services/Domain_calc2/FeatureServer?token=E... 

You can find the URL for the rest endpoint on the item details page. It is on the bottom right of the page in a section called URL.

[ChristopherMugdan]

The "extent" I am referring to here is the one that is in the response to a request of the form:

https://<portal url>/sharing/rest/content/users/<user name>?num=10&f=json&token=<token>

and the extent information appears to be in decimal degrees for the web map I have created. I want to know what CRS that extent is in. Below is a snippet of the response.

Also, do you know the answer to my question about how to find what units the web map is in?

Cheers,

Chris

.......

        "type": "Web Map",
        "typeKeywords": ["ArcGIS Online",
        "Explorer Web Map",
        "Map",
        "Online Map",
        "Web Map"],
        "description": null,
        "tags": ["Australia test"],
        "snippet": "Australia test map",
        "thumbnail": "thumbnail/_7B13F314F4-7C86-4F95-B767-FE0871E20C3F_7D.png",
        "documentation": null,
        "extent": [[100.922048628469,
        -45.0493616849178],
        [163.716670827299,
        -7.28393079517143]],
        "categories": [],
        "spatialReference": null,
        "accessInformation": null,
        "licenseInfo": null,
        "culture": "english (united states)",

.......