HERE Maps API - How to change map zoom level and center point
In this article we will introduce the map zoom level and map center.
Ovi Maps API supported web browser (basically any modern web browser)
The example assumes you have already added the Ovi Maps to your web page as explained in the previous article "Ovi Maps - Add Maps To Any Web Page"
Important about Maps credentials
With Ovi Maps API you can start without having any credentials given, but you might face a performance gap. In order to get the full potential out of the offering, you must get the credentials that authenticate your application against the Services. Please read through the Location API.
Note: At the time of writing, it is not necessary to include the token. Please follow the Announcement section for Ovi Maps at Nokia Projects. It will be updated when the authentication is enabled on the backend servers.
You can change the parameters for the map view by passing them to the previously instantiated Display (handled in the article "Ovi Maps - Add Maps To Any Web Page") that define the zoom level and center point for the map can be set to suite your purposes. The map will default in our example to Berlin, Germany but you can ofcourse change this the center to point to any other location on this planet.
The map center is defined by the center property and must be provided in type of ovi.mapsapi.geo.ICoordinate and defined as follows:
new ovi.mapsapi.geo.Coordinate (lat, lng, [alt, [skipValidation]])
The coordinate represents a geographical position. Altitude is defined as optional. (For more details on this see the Maps API reference).
Note: There is an article about the coordinate system and geocoordinates titled: "Ovi Maps API - Geocoordinates". You may want to check it out for more detailed information on the geocoordinate system used in Ovi Maps and some generic information about the world coordinate system.
In our example we will use the latitude and longitude values for the city of Dusseldorf, Germany : 52.51, 13.4. These will be passed in form [52.51, 13.4]. The latitude and longitude can be passed as a floating point number, i.e. 13.4 is just as valid as e.g. 13.456789
[b]zoomLevel[/b] The map zoom level is defined by this property
The zoomLevel is a number between minimum and maximum values and can be queried with minZoomLevel() and maxZoomLevel() methods.
At the moment, the API offers the scale of zoom between 0 (zero) and 20. This is reflected from the UI component ZoomBar on the Map view. The UI component used exact zoom levels respectively are:
Example of requesting the min and max zoom levels of the current map:
map.minZoomLevel <- Could return example "0" (zero)
map.maxZoomLevel <- Could return example "20"
This code will add the zoomLevel and center point. Please visit the article "Ovi Maps API - Add Maps To Any Page", there the Example code is divided in two: Example 1 and 2. The code below is what is added to the Example 1, thus making the map to position itself somewhere else than the coordinate 0,0 as is by default and setting the zoom level to be > 0. The default zoom level if not specified, is zero (0).
'zoomLevel': 8, // Country level
'center': [52.51, 13.4] // New map center point
When you have defined these, the map should open on Country level of zoom, having the city of Dusseldorf, Germany in the middle of the map view.
For more on Ovi Maps API
Please check out the Ovi Maps API full documentation and API reference here:
Google Chrome 11.0x Mozilla Firefox 5.0