[OpenLayers-Users] projection in openlayers

[maven apache]

Hi:

I am using openlayers 2.13.1, and  I meet some problems when dealing with
the projection.

1 Change the projection on the fly.

Say I have to baselayers:

var osm=new OpenLayers.Layer.OSM();  // whose projection is "EPSG:900913"

var l4326=new Custome4326Layer();  // whose projection is "EPSG:4326"

Now I want to switch between the two base layers.

But it seems that ol does not support this out of the box. so  I do some
fix job:

var setBaseLayer = ol.Map.prototype.setBaseLayer;
ol.Map.prototype.setBaseLayer = function (baseLayer) {
    var oldProjection = new ol.Projection(this.projection);
    var newProjection = baseLayer.projection;

    var oldZoom = this.getZoom();
    var oldCenter = this.getCenter();
    setBaseLayer.apply(this, arguments);
    if (newProjection) {
        this.projection = newProjection.getCode();
        this.maxExtent = baseLayer.maxExtent;
        this.maxResolution = baseLayer.maxResolution;
        this.resolutions = baseLayer.resolutions;
    }
    if (!newProjection.equals(oldProjection) && oldCenter) {
        var newCenter = oldCenter.transform(oldProjection, newProjection);
        this.setCenter(newCenter, oldZoom);
    }
}

It seems this works, when I change to another projection, the new tiles
will be loaded correctly at least.

But the vector data are not re-projected. For example, when the `osm` is
the baselayer, and I add a marker to the map, when I change to `l4326`, the
marker will disappeared since its location is not re-projected.

So is the instances of `Feature.Vector` and etc.  Of course, I can hold the
reference to each feature,marker added to the map, and re-project them
manually,but I wonder if there is a better choice.


2 Add custom project

We have tiles with projection neither 4326 or 3857, so we can not use the
internal projection transformation out of box, however I do not find
anything about create custom projection and register the related transform
methods.

All I found is something like:

var pro=new ol.Projection("EPSG:4326")

which can not meet my requirements.

Did I  miss anything?


Yang
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