You can call your python method through your .js file using .call method.

for example,

I assume, your class name is 'my.module', then you can call your method, using following way.

var MyModel = new Model('my.module')

MyModel.call('tt_js_return_url', []).then(function(result){

// your code , in result you will get value returned by python method.

});

Hi,

I am not sure that I understand you correctly. What i am imagining :

In your front end html site:

<script src="odoo_js_files.js"/>
<script src="your_file.js"/>
<script src="google_map.js"/>

If that is true, please read https://www.odoo.com/documentation/8.0/howtos/web.html too know how to insert your js files when Odoo render the page, and call your tt_js_return_url as describled in  Communication with the Odoo Server section.

After your call to server, you'll get long+lat, assign it to a global variable to make it available in your google_map.js.

Hope this helps.

UPDATE:

I can think of 2 ways to do this:

1.

If your html page is in a separated application from Odoo, you may write kind of webservice in Odoo and call it from your maps application.

Odoo                                                                                                           Maps application

end point:                                                      

http://yourodoo.com/get_vehicle_cordinates        <--------------->              Javascript client

At odoo side, you should write a method in a controller like this:

@http.route(route='/get_vehicle_cordinates', auth='public') # consider authorization check
    def get_vehicle_cordinate(self, **kwargs):
    # And calculate cordinates to return

And at Maps side, you should use JavaScript to call that service, use something like $.post('http://yourodoo.com/get_vehicle_cordinates', {vehicle_id: v_id}, function(){

    // Handle your long, lat value.

})

2. The second way, if your html page is a part of Odoo, you may put your map in a Odoo widget.

Define html code in a template,  use call method (please read Communication with the Odoo Server which I mentioned above) to call tt_js_return_url and handle the result

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