Is there only one projection in OpenLayers map?

Is there only one projection in OpenLayers map?

Every map that you’ll create with OpenLayers will have a view, and every view will have a projection. As the earth is three-dimensional and round but the 2D view of a map isn’t, we need a mathematical expression to represent it. Enter projections. There isn’t only one projection, but there are many common ones.

How big is the center of view in OpenLayers?

Chances are that your map looks like this: Here [-77.036667, 38.895] is provided as the center of the view. But as Web Mercator is a metric projection, you are currently telling OpenLayers that the center shall be some meters (~77m and ~39m respectively) away from [0, 0].

Why are there so many questions about OpenLayers?

Certain questions arise more often than others when users ask for help. This document tries to list some of the common questions that frequently get asked, e.g. on Stack Overflow. If you think a question (and naturally its answer) should be added here, feel free to ping us or to send a pull request enhancing this document.

Why do I get wrong coordinates in OpenLayers?

If you have set a center in your map view, but don’t see a real change in visual output, chances are that you have provided the coordinates of the map center in the wrong (a non-matching) projection. As the default projection in OpenLayers is Web Mercator (see above), the coordinates for the center have to be provided in that projection.

Which is the best way to use OpenLayers?

OpenLayers has some helpful utility methods to assist you: The method fromLonLat () is available from version 3.5 onwards. If you told OpenLayers about a custom projection (see above), you can use the following method to transform a coordinate from WGS84 to your projection:

How to draw a polygon from existing lonlat points?

OpenLayers – how do I draw a Polygon from existing lonLat points? I have in my database longitude-latitude verticies from user-defined polygons. My questions is: how do I recreate and display them on a map now? This is quite easy to do with the Google Maps API, but I can’t find any documentation or examples on how to do this with OpenLayers.

How does raster reprojection work in OpenLayers?

Raster Reprojection. OpenLayers has an ability to display raster data from WMS, WMTS, static images and many other sources in a different coordinate system than delivered from the server. Transformation of the map projections of the image happens directly in a web browser.

When to pass reprojectionerrorthreshold option in OpenLayers?

In case a different threshold needs to be defined for different sources, the reprojectionErrorThreshold option can be passed when constructing the tile image source. The reprojection algorithm uses inverse transformation (from view projection to data projection ).

Which is the default mapping property in OpenLayers?

The OpenLayers default is to construct maps in a geographic projection so in this case, as on the previous examples it shouldn’t be needed. The second thing to note is the use of the restrictedExtent property. This optional property restricts map panning to the given bounds. The imagery data used by the tiger-nfc layer is limited to these bounds.

Do you need a coordinate system for OpenLayers?

As everything is fictional, you don’t need/have a coordinate system or map projection or you just use the defaults like for Google Maps. With OpenLayers, it might work like this. For the second one, you might play with existing (offline) renderers like Tilemill or Maperitive.

How to build an OpenLayers application for production?

For production, we strongly recommend bundling the application together with its dependencies, as explained in the Building an OpenLayers Application tutorial. Below you’ll find a complete working example. Create a new file, copy in the contents below, and open in a browser: To include a map a web page you will need 3 things:

How to detect zoom change in OpenLayers-geographic..?

I noticed that exposed method view.animate is called before any animated map event. I replaced it with my own, where I check for zoom, and then call original method: Thanks for contributing an answer to Geographic Information Systems Stack Exchange! Please be sure to answer the question.

Why does OpenLayers not update the map when the container is resized?

OpenLayers does not update the map when the container element is resized. This can be caused by progressive updates to CSS styles or manually resizing the map. When that happens, any interaction will become inaccurate: the map would zoom in and out, and end up not being centered on the pointer.

When to use the same projection in Bing Maps?

The same projection is used e.g. for the maps of the OpenStreetMap-project and commercial products such as Bing Maps or Google Maps. This projection is a good choice if you want a map which shows the whole world, and you may need to have this projection if you want to e.g. use the OpenStreetMap or Bing tiles.