Why zoom level returns decimal?

Question

I use openlayers 6 in my project. Layers on the map hide/show acording to zoom level.

Here is map and view defenitions:

view = new View({
    center: mapCenter,
    projection: israeliTM.getCode(),
    zoom: 0,
    resolutions: resolutions // resolutions array 
});

map = new Map({
    layers: layers,
    target: 'map',
    view: view
});

This row is fired when zoom is changed:

var curRes = map.getView().getResolution()[map.getView().getZoom()];

As you can see on view defenition resolutions defined as array and when zoom is changed I expect to get from this map.getView().getZoom() integer number that displays index in resolutions array and return current resolution. In general it works as expected but sometimes map.getView().getZoom() returns decimal number like 3.56989.

Any idea why map.getView().getZoom() returns some time decimal?

Mike Mike · Accepted Answer · 2019-11-22T13:03:22

If you are using OpenLayers 6 specify constrainResolution in the view options

view = new View({
    center: mapCenter,
    projection: israeliTM.getCode(),
    zoom: 0,
    constrainResolution: true,
    resolutions: resolutions // resolutions array 
});

and for OpenLayers 5 specify constrainResolution in the interaction options

map = new Map({
    layers: layers,
    target: 'map',
    interactions: defaultInteractions({
        constrainResolution: true
    }),
    view: view
});

Why zoom level returns decimal?

2 Answers