Saturday, 13 July 2019

coordinate system - Question Regarding Interpretation of Openlayers BBOX in 4326 Projection


I have a BBOX strategy in my Vector layer, which is sending HTTP GET Requests to my server in order to get the features I wish to display. The projection of the layer is EPSG:4326, so it is my understanding that the bounding box should contain the coordinates of the lower left corner and the upper right corner in longitude/latitude format.


It appears that the bounding box extends beyond the current view of the map on all sides. This makes sense as a way to allow for small lateral shifts of the map view without the need for a new data request. However, for some zoom levels I am also getting numbers outside of the range of -180 to 180 degrees for longitude and -90 to 90 degrees for latitude (e.g., -453). Am I correct in assuming that these still represent degrees, and that I should just compute their value modulo 360 or 180, etc?


I just want to make sure that I am understanding what OpenLayers is providing for the BBOX, since I have so far been unable to find it written down anywhere.




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