I am new to creating maps using HTML and I have been attempting to add two vector layers (places, points) to a base map (roads), however I cannot see the vector layers on the map. The layers should appear as vector overlays to the base map. The layers are there as they are being shown in the layer switcher, but are not being displayed on screen. I believe the problem is to do with the way the vectors layers are being called. What is the solution to get the vector layers to be displayed. Thanks
var map = new OpenLayers.Map("map-id");
var roads= new OpenLayers.Layer.WMS(
"roads",
"http://localhost:8080/geoserver/wms",
{layers: "roads"});
var points= new OpenLayers.Layer.Vector(
"points",
"http://localhost:8080/geoserver/wms",
{layers: "points"});
var places= new OpenLayers.Layer.Vector(
"places",
"http://localhost:8080/geoserver/wms",
{layers: "places"});
map.addLayer(roads);
map.addLayer(points);
map.addLayer(places);
map.addControl(new OpenLayers.Control.LayerSwitcher());
You are trying to display your vector data through WMS protocol. For this purpose you should use OpenLayers.Layer.WMS instances instead OpenLayers.Layer.Vector. For displaying WMS layer as overlay use isBaseLayer option:
map = new OpenLayers.Map('map');
var places = new OpenLayers.Layer.WMS('places',
"http://localhost:8080/geoserver/wms",
{layers: "places", transparent: true},
{isBaseLayer: false, opacity: 1, singleTile: true, visibility: true}
);
map.addLayers([places]);
Related
I followed the example from the openlayers book to add a static image on top of an osf layer. It works, but my image (256x256) is displayed as a rectangle. I tried around with the coordinates for the projection and checked out other posts here on, but I can't get my head around it why the image is not displayed as a square:
// Create map
var map = new ol.Map({
target: 'map', // The DOM element that will contains the map
renderer: 'canvas', // Force the renderer to be used
layers: [
// Add a new Tile layer getting tiles from OpenStreetMap source
new ol.layer.Tile({
source: new ol.source.OSM()
})
],
// Create a view centered on the specified location and zoom level
view: new ol.View({
center: ol.proj.transform([16.3725, 48.208889], 'EPSG:4326', 'EPSG:3857'),
zoom: 4
})
});
// Create an image layer
var imageLayer = new ol.layer.Image({
opacity: 0.75,
source: new ol.source.ImageStatic({
attributions: [
new ol.Attribution({
html: ''
})
],
url: 'https://placebear.com/256/256',
imageSize: [256, 256],
projection: map.getView().getProjection(),
imageExtent: ol.extent.applyTransform(
[0, 0, 16.3725, 48.208889], ol.proj.getTransform("EPSG:4326", "EPSG:3857"))
})
});
map.addLayer(imageLayer);
ol.source.ImageStatic was made to put a georeferenced image (e.g. a scan of a historic map) on a map. Is this what you have in mind? If you just want to display an image and anchor it to a location on the map, you'd better use ol.Overlay or an ol.layer.Vector with a feature with an ol.style.Icon.
That said, your image will only be displayed as square if the imageExtent set on your ol.source.ImageStatic results in a square on the projected map view.
I have created a map found here: http://userpages.flemingc.on.ca/~eluli/collab.html
Users can toggle between the different layers on the map. As you can see, whenever a user toggles at a new layer, the map extents to the new layer. How can I make so that this does NOT happen? For example, if a user has zoomed into a specific area, I want the map to remain at the same extent whenever a new layer is checked on.
I have written code which has the initial map extents (I deleted the extent in order to experiment but when I did that, the map does not show up).
function initialize() {
var ontario = new google.maps.LatLng(49.2867873, -84.7493416);
var mapOptions = {
zoom: 5,
center: ontario,
styles: ....
var kmlOptions = {
suppressInfoWindows: true,
preserveViewport: false,
map: map
};
//Layer 0
layers [0] = new google.maps.KmlLayer('https://docs.google.com/uc?authuser=0&id=0B79b02nBK5vkVGVwdnEtS1puTlE&export=download',
{preserveViewport: false, suppressInfoWindows: true});
//Layer 1
layers [1] = new google.maps.KmlLayer('https://docs.google.com/uc?authuser=0&id=0B79b02nBK5vkdE9DRmxzRHdCN28&export=download',
{preserveViewport: false, suppressInfoWindows: true});
.........................
Let me know if I need to show more of my code
{preserveViewport: true} will keep KmlLayer from zooming to fit its contents
I use the following block of JavaScript to try to show a WMS layer. I'm using OpenLayers 2.8.
The map's base layer (Openstreetmap) shows correctly, it zooms to the correct area, the "pyramid" layer is shown in the layer switcher, but no request to its WMS service is ever made (so the fact that the URL, styles and params are dummies shouldn't matter -- it never even attempts to get them).
OpenLayers does try to get a WMS layer once I pan or zoom far enough so that the Gulf of Guinea is in view (but all my data is in the Netherlands). This suggests a projection problem (WGS84's (0, 0) point is there), but I don't understand why OpenLayers doesn't even try to fetch a map layer elsewhere. My data is in EPSG:3857 (Web Mercator) projection.
/*global $, OpenLayers */
(function () {
"use strict";
$(function () {
$(".map").each(function () {
var div = $(this);
var data_bounds = div.attr("data-bounds");
console.log("data_bounds: " + data_bounds);
if (data_bounds !== "") {
var map = new OpenLayers.Map(div.attr("id"), {
projection: "EPSG:3857"});
var extent = JSON.parse(data_bounds);
var bounds = new OpenLayers.Bounds(
extent.minx, extent.miny,
extent.maxx, extent.maxy);
map.addLayer(
new OpenLayers.Layer.OSM(
"OpenStreetMap NL",
"http://tile.openstreetmap.nl/tiles/${z}/${x}/${y}.png",
{buffer: 0}));
map.addLayer(
new OpenLayers.Layer.WMS(
"pyramid", "http://rasterserver.local:5000/wms", {
layers: "test",
styles: "test"
}, {
singleTile: true,
isBaseLayer: false,
displayInLayerSwitcher: true,
units: 'm'
}));
map.addControl(new OpenLayers.Control.LayerSwitcher());
map.zoomToExtent(bounds);
}
});
});
})();
Edit: the 'data_bounds' console print prints (with some added formatting):
data_bounds: {
"minx": 582918.5701295201,
"miny": 6923595.841021758,
"maxx": 821926.9006116659,
"maxy": 7079960.166533174
}
It zooms to the correct region in the north of the Netherlands, so I don't think the problem is there.
Since posting, I found out that if I don't use the OSM layer, and instead use the WMS layer as baselayer, it works. So perhaps there's some incompatibility with a OSM baselayer and a WMS layer added to it? But then I don't get that it does seem to do something near WGS84 (0, 0).
I eventually managed to fix this by giving the map an explicit maxExtent:
var extent = JSON.parse(data_bounds);
var bounds = new OpenLayers.Bounds(
extent.minx, extent.miny,
extent.maxx, extent.maxy);
var map = new OpenLayers.Map(div.attr("id"), {
projection: "EPSG:3857",
maxExtent: bounds
});
Oddly enough this doesn't limit the user's ability to pan and zoom around the world, but it does make the overlay work...
I'm trying to show a map with three layers (google maps layers, wms layer and points layer) this is my code:
var map = new OpenLayers.Map({
div: "map",
maxExtent: new OpenLayers.Bounds(-20037508, -20037508, 20037508, 20037508.34)
});
var capaGoogle = new OpenLayers.Layer.Google(
"Google Satellite",
{ type: G_SATELLITE_MAP, sphericalMercator: true, transparent: true }
);
var wmsOverlay = new OpenLayers.Layer.WMS("OpenLayers WMS",
"http://localhost:1979/geoserver/wms",
{ layers: 'world:PYCIUDADES', transparent: true }, { isBaseLayer: false });
var vectorLayer = new OpenLayers.Layer.Vector("vector");
vectorLayer.addFeatures([
new OpenLayers.Feature.Vector(
new OpenLayers.Geometry.Point(-57.635021, -25.276987)
),
new OpenLayers.Feature.Vector(
new OpenLayers.Geometry.Point(-56.759034, -22.71539)
)
]
);
map.addLayers([wmsOverlay, vectorLayer, capaGoogle]);
map.addControl(new OpenLayers.Control.LayerSwitcher());
var center = new OpenLayers.LonLat(-57.58, -25.27).transform(
new OpenLayers.Projection("EPSG:4326"),
map.getProjectionObject()
)
map.setCenter(center, 6);
the "vectorLayer" layer must be above of my map, but I get this (my wms layer is in south america, my points have to be also in south america, but they're near africa):
http://i45.tinypic.com/34y40zk.png
What can I do?
Thanks in advance
You should to transform your point's coordinates:
var epsg4326 = new OpenLayers.Projection('EPSG:4326');
var epsg900913 = new OpenLayers.Projection('EPSG:900913');
vectorLayer.addFeatures([
new OpenLayers.Feature.Vector(
new OpenLayers.Geometry.Point(-57.635021, -25.276987).transform(epsg4326, epsg900913)
),
new OpenLayers.Feature.Vector(
new OpenLayers.Geometry.Point(-56.759034, -22.71539).transform(epsg4326, epsg900913)
)
]);
"next to Africa" = longitude 0 latitude 0
when you simply enter Longitude and Latitude, OL considers this a WGS84 projection (standard).
but since you are using a Google layer (CapaGoogle), which is a mercator-referenced projection, you end up using two reference projections (4326 = WGS84 AND 900913 = mercator) simultaneously and the map server disconsiders the location of your markers, since they are "incorrect". therefore, it simply places them at (0,0).
as DrNextGIS said, you must "transform your points coordinates" so that everything on your map uses the same projection.
you would NOT have this problem if you were using a simple OpenLayer map (without Google or OSM).
I've been at this all day long and honestly I'm out of ideas. I have some WMS layers that I would like to display/not display depending on the current zoom level. Yes, I have went through the API docs and they seem to be clear as day, but I follow everything that is suggested and I'm not getting the results desired :(
This was one of the sources that I looked at:
http://trac.osgeo.org/openlayers/wiki/SettingZoomLevels
Then to make matters even worse I found out that if you have an Open Street Map base layer displaying on load it seems to limit your control over the map's numZoomLevels, just what I needed, since I DO want to use this as my loading base layer...
So my questions are:
What am I doing wrong?
Is it true that there really is no workaround on the control of zoom levels when using an Open Street Map base layer on load? Or is there something I just don't know?
Here are some of my code attempts:
Take 1: tib_villages layer should only show when the zoom level is 8-10, doesn't work!
var options = {
controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
units: 'm',
numZoomLevels: null, //setting the map's zoom levels to null
allOverlays: false
}
var osm = new OpenLayers.Layer.OSM(); //MY base layer
//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
"Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: 10, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
);
Take 2: tib_villages layer should only show when the zoom level is 8-10, map should only have 10 zoom levels, but instead has 19 as the Open Street Map Layer enforces it to, doesn't work!
var options = {
controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
units: 'm',
numZoomLevels: 10, //setting the map's zoom levels to 10 only
allOverlays: false
}
var osm = new OpenLayers.Layer.OSM(); //MY base layer
//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
"Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: null, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
)
;
Take 3: After getting rid of the Open Street Map base layer on load, the map only has 10 zoom levels as specified, but tib_villages layer should only show when the zoom level is 8-10, doesn't work!
var options = {
controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
units: 'm',
numZoomLevels: 10, //setting the map's zoom levels to 10
allOverlays: false
}
//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
"Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: 10, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
);
All of your suggestions are sincerely appreciated!
elshae
Try to use minResolution and maxResolution instead of minZoomLevel. It usually works fine. You can get resolution for any zoom lever if you call map.getResolution() method.
Another option is to listen to OpenLayers.Map's zoomend event and toggle layer visibility accordingly. Something like this:
map.events.on({ "zoomend": function (e) {
if (this.getZoom() > 2) {
layer1.setVisibility(false);
layer2.setVisibility(true);
}
else {
layer2.setVisibility(false);
layer1.setVisibility(true);
}
}
});
I would recommend using the maxScale and minScale on the layers instead of resolution, but that maybe is a question of taste. :-) I can't relate to a resolution value, but a scale is easy to understand and to maintain in the longer run, when others look at your code.