Count of documents based on site column content across multiple site collections?

Question

I have a requirement for a dashboard and wondering how to implement in best possible way.

I guess CSOM + REST is the only option

Requirement:

1. Have multiple site collections with one Document Library.
2. The Document Library is based on site Content Type.
3. The site Content Type has 2 Managed Metadata based Site Columns "Document Type" & "Location".
4. "Document Type" column has a standard set of values e.g Type 1, Type 2, Type 3, Type 4 & Type 5
5. "Location" column has a standard set of values e.g Loc 1, Loc 2, Loc 3, Loc 4 & Loc 5
6. The user who views the dashboard may or may not have access for all site collections

Now a dashboard is needed in one of the site collection which will parse the Document library across other multiple site collections and fetch the count as show below.

                       Type 1     Type 2     Type 3     Type 4     Type 5

        Site 1            100         50         50         150        20
        -Loc 1             20         10         10          30         4
        -Loc 2             20         10         10          30         4
        -Loc 3             20         10         10          30         4
        -Loc 4             20         10         10          30         4
        -Loc 5             20         10         10          30         4

        Site 2             40         60         50         150        20
        -Loc 1             10         10         10          30         4
        -Loc 2             10         10         10          30         4
        -Loc 3             10         10         10          30         4
        -Loc 4              5         10         10          30         4
        -Loc 5              5         20         10          30         4

All suggestions are welcomed & Thanks in advance.

Answer 1

You have to Create your Content Type as Content Type Hub after that your Content type will appear in all site collection of your web application for more info about you can refer below links http://www.sharepointpals.com/post/How-to-Use-Content-Type-Hub-in-SharePoint-2013

http://www.c-sharpcorner.com/UploadFile/40e97e/create-content-type-hub-in-sharepoint-2013/