Can you pass coordinate values as variables when trying to retreive an external GeoJSON data source? Ideally I'd like to pass something like this, but it doesn't work for me.
map.addSource('geojsonpoints', {
type: "geojson",
data: 'http://myexample.com/pins?lat={lat}&lon={long}'
});
I am able to pass Z, X, Y coordinates if I use Map Vector Tiles (mvt) as a source. i.e. This works:
map.addSource('mapvectortiles', {
'type': 'vector',
'tiles': ['http://myexample.com/{z}/{x}/{y}'],
But I haven't figured out how to do it for a GeoJSON source. Anyone have any ideas if it is possible in n Mapbox GL JS?
FYI, I am able to generate the URL using the method below, but the problem is it doesn't refresh when I move the map, unlike vector tiles.
var lng = map.getCenter().lng
var lat = map.getCenter().lat
var url = 'http://myexample.com/pins?lat='+lat+'&lon='+lng
map.addSource('EPC', {
type: "geojson",
data: url
});
I use GeoJSON to draw Tiles on the map
this is a sample GeoJSON:
{ "type": "FeatureCollection",
"features": [
{ "type": "Feature",
"geometry": {
"type": "Polygon",
"coordinates": [
[
[4.342254780676343, 50.89533552689166],
[4.342254780676343, 50.89443721160754],
[4.340830581474948, 50.89443721160754],
[4.340830581474948, 50.89533552689166],
[4.342254780676343, 50.89533552689166]
]
]
},
"properties": {}
}
]
}
after all you have to add the source and add the layer
add Source:
const sourceJson: GeoJSONSourceRaw = {
type: 'geojson',
data: data as FeatureCollection
};
map.addSource(sourceId, sourceJson)
data is your json file
add Layer:
const layer: FillLayer = {
id: sourceId,
source: sourceId,
type: 'fill',
paint: {
'fill-color': color,
'fill-opacity': opacity
}
}
this.map.addLayer(layer);
There are two parts to your question:
Update the data source when the map is moved
Use the map's extent as part of the GeoJSON source's URL.
You have part 2 under control, so:
Update the data source when the map is moved
Use map.on('moveend', ...
Use map.getSource(...).setData(...)
Related
I've been trying to get Leaflet to display a geojson file using the styles described in the geojson file, and I can't get it to work. The geojson below shows that I've got styles in there - OGR style pen etc, but I've tried extracting them using style function(styles) {return {colour : data.properties.pen}}, but it gives me an error on the console - but not enough errors to match the number of layers - so I can understand that some layers may not have a "pen" property, but none of the layers are coming up with the any differences.
"features": [
{ "type": "Feature", "properties": { "Layer": "Buildings", "SubClasses": "AcDbEntity:AcDb2dPolyline", "EntityHandle": "2ABF", "OGR_STYLE": "PEN(c:#ff7f00,p:"1.2g 0.72g 0.12g 0.72g")" }, "geometry": { "type": "LineString", "coordinates": [ [ -1.386274792183286, 54.907452998026585, 0.0 ], [ -1.386201193400163,
In fact, as the above geojson shows, it's actually a geometry - but all that's showing up is a marker, which is my second problem. Can anyone point me to some example codes or anything which may help me?
$.getJSON(address, function(data) {
//add GeoJSON layer to the map once the file is loaded
layer[i] = L.geoJson(data, {style: function(styles) {
return {color: data.properties.pen,
weight: data.properites.weight
};
onEachFeature: onEachFeature
}
}).addTo(map);
Thanks.
Change your code to:
function onEachFeature(feature, layer) {
if (feature.properties && layer instanceof L.Path) {
layer.setStyle({
color: feature.properties.pen,
weight: feature.properites.weight
});
}
}
$.getJSON(address, function(data) {
//add GeoJSON layer to the map once the file is loaded
layer[i] = L.geoJson(data, {
onEachFeature: onEachFeature
}).addTo(map);
});
Leaflet GeoJson Tutorial
with QGIS I´ve exported a polygon layer as geojson which I´d like to publish with leaflet. This is how the geojson looks like [exluded due to SO character limits]:
https://gist.github.com/t-book/88806d12d7f05024b147715be82e6844
This is what I´ve tried:
Wrapped geojson as var:
var states = [{
"type": "FeatureCollection",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:EPSG::31468" } },
"features": [
{ "type": "Feature", "properties": ...
}];
Added as new Layer:
L.geoJSON(states, {
style: function(feature) {
switch (feature.properties.party) {
case 'Euerbach': return {color: "#ff0000"};
case 'Werneck': return {color: "#0000ff"};
}
}
}).addTo(map);
Unfortunately nothing is rendered. How do I correctly add this geojson featureCollection to my map?
The problem is that your data is projected - Leaflet is expecting your data to be unprojected (composed of long/lat pairs, or "projected" in WGS84/EPSG 4326). There are a few solutions, two come to mind here:
In QGIS, export your data so that it is composed of long/lat coordinate pairs
Use proj4.js to reproject your coordinates when displaying the geojson.
For number two, you'll need to set the coordsToLatLng option when adding the geojson as a layer:
var geojson = L.geoJSON(states, {
coordsToLatLng: function (p) {
// return get lat/lng point here.
})
The body of this function will take a coordinate in the geojson's coordinate reference system (CRS) and return it in WGS84 using proj4.
Also, coordsToLatLng function expects you to return lat/long pairs. As your geojson and proj4 represent data that is [x,y], we need to swap our values before returning the new point.
This could look like:
var geojson = L.geoJSON(states, {
coordsToLatLng: function (p) {
p = proj4(fromProjection,toProjection,p); // reproject each point
p = [p[1],p[0]] // swap the values
return p; // return the lat/lng pair
}
}).addTo(map);
Of course, we need to define our CRSs. I looked up your CRS (it is specified in the geojson itself) on spatialreference.org and used the provided description for that CRS and EPSG4326 (WGS84) to set my fromProjection and toPojection:
var fromProjection = '+proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 +ellps=bessel +datum=potsdam +units=m +no_defs ';
var toProjection = "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs ";
Altogether that gives us something like this.
Keep in mind, that if you have large files, reprojecting them in javascript will take longer than if you export them in the proper CRS.
I would like to add a custom marker to my map. I am using a mapbox gl script.
The only documentation that I found related to this topic is this one https://www.mapbox.com/mapbox-gl-js/example/geojson-markers/.
I tried to customize given example and I managed to add a marker and modify it a little changing the size, but since I don't understand all the parameters, I don't know how to add my own marker. Is there any documentation that is more detailed?
Here is my code:
<script>
mapboxgl.accessToken = 'pk.eyJ1IjoiYWl3YXRrbyIsImEiOiJjaXBncnI5ejgwMDE0dmJucTA5aDRrb2wzIn0.B2zm8WB9M_qiS1tNESWslg';
var map = new mapboxgl.Map({
container: 'map', // container id
style: 'mapbox://styles/aiwatko/cipo0wkip002ddfm1tp395va4', //stylesheet location
center: [7.449932,46.948856], // starting position
zoom: 14.3, // starting zoom
interactive: true
});
map.on('load', function () {
map.addSource("markers", {
"type": "geojson",
"data": {
"type": "FeatureCollection",
"features": [{
"type": "Feature",
"geometry": {
"type": "Point",
"coordinates": [7.4368330, 46.9516040]
},
"properties": {
"title": "Duotones",
"marker-symbol": "marker",
}
}]
}
});
map.addLayer({
"id": "markers",
"type": "symbol",
"source": "markers",
"layout": {
"icon-image": "{marker-symbol}-15",
"icon-size": 3
}
});
});
</script>
Thanks in advance!
Oktawia
There are two ways to customize markers in Mapbox.
Raster Markers in Mapbox
See this link on Mapbox.com for Custom marker icons. That example shows how to use a .png as a marker.
SVG Markers in Mapbox
You are pretty close to modifying the icons, but take some time to familiarize yourself with the parameters.
The icon-image may be the harder one to understand. It takes the property "marker-symbol": "marker" from the GeoJson, and "icon-image": "{marker-symbol}-15", to create the final result of marker-15.
This brings up a further question: where/how are the markers defined?!?
The markers also come from Mapbox and are called Maki Icons. You can change the "marker-symbol" to aquarium or cafe to see the results.
From the Mapbox GL Style Reference
icon-size — Scale factor for icon. 1 is original size, 3 triples the size.
icon-image — A string with {tokens} replaced, referencing the data property to pull from.
I understood that I can use the general Leaflet layer, and the more advanced map-box featureLayer, that provides useful functions as the filter.
However, I don't understand the difference between
marker = L.Marker (new L.LatLng(lat, lng),
{
icon: L.mapbox.marker.icon(
{'marker-color': 'fc4353'
'marker-size': 'large'
}),
title: name,
});
map.addLayer(marker);
and
var poijson = {
"type": "Feature",
"geometry": {
"type": "Point",
"coordinates": [lng, lat]
},
"properties": {
"title": poi.name,
"marker-color": "#fc4353",
"marker-size": "large"
}
};
map.featureLayer.setGeoJSON(geojson);
Is it just the same?
[UPDATE]
Moreover, if I had many markers, should I add a new layer for each marker? It seems not a good thing for performance..
For instance, If I do:
var pois; //loaded with pois info
var geojson=[]; //will contain geojson data
for (p=0; p< pois.length; p++)
{
var poi = pois[p];
var poijson =
{
"type": "Feature",
"geometry":
{
"type": "Point",
"coordinates": [poi.lng, poi.lat]
}
};
geojson.push(poijson);
}
map.featureLayer.setGeoJSON(geojson);
Does it will create many layers for each poi, or just one layer with all the markers?
thank you
When you add a marker to a Leaflet map via map.addLayer(marker);, the marker is added to the 'leaflet-maker-pane'. The markers are plain images/icons.
You can use a geoJSON layer to draw GIS features: points, lines, polygons, etc.
See here: http://leafletjs.com/examples/geojson.html
Mapbox's featureLayers is just an extension to Leaflet's geoJSONLayer
To add multiple markers, call addMarker multiple times. Leaflet will create a new layer for each of the markers. Each marker will be added as an image element to the leaflet-marker-pane div:
http://bl.ocks.org/d3noob/9150014
Updated response:
If you add a GeoJSON layer with multiple features, Leaflet will create separate layer for each of the features. You can inspect the layers of the map by calling map._layers after adding the GeoJSON Layer.
marker.addTo(map) and map.addLayer(marker) are doing the same thing.
Here's the addTo function taken from the source
addTo: function (map) {
map.addLayer(this);
return this;
},
I'm using L.geoJson and adding layer to my map, then with items.on('click', function (event) {}) displaying info of selected object which is stored in event.layer (getting info with toGeoJSON()).
Problem is, when there are some of the items, everything seems to work, but now when there are >1000 polygons, some of the data when using on('click') does not contain my info of the feature inside event.layer.
What could be a problem?
ADDITIONAL INFO:
Our GeoJSON looks something like this, it has additional data like ID and various properties.
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"id": 1,
"geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
"properties": {"prop1": "value1"}
},
{
"type": "Feature",
"id": 2,
"geometry": {"type": "Point", "coordinates": [142.0, 15.5]},
"properties": {"prop1": "value2"}
}
]
}
I put everything on a map:
data = L.geoJson(data);
allItems.clearLayers().addLayer(data);
Features are displayed on a map.
Then I listen for clicks on the features on the map:
allItems.on('click', function (event) {
// On many of the features this is empty,
// on some data can be retrieved.
// On some that doesn't have ID, properties
// are empty too
console.log(event.layer.toGeoJSON().id);
});
GeoJSON has been checked and ID and properties ARE THERE.
Here's a little explanation about how to handle click events on L.GeoJSON layer and/or it's features. I've commented the code to explain what is going on and added an example on Plunker for you so you can test the concept.
Example on Plunker: http://plnkr.co/edit/TcyDGH?p=preview
Code:
var geoJsonLayer = L.geoJson(data, {
// Executes on each feature in the dataset
onEachFeature: function (featureData, featureLayer) {
// featureData contains the actual feature object
// featureLayer contains the indivual layer instance
featureLayer.on('click', function () {
// Fires on click of single feature
console.log('Clicked feature layer ID: ' + featureData.id);
});
}
}).on('click', function () {
// Fires on each feature in the layer
console.log('Clicked GeoJSON layer');
});
As for your code, i'm quite confused as to where the allItems comes from. A layerGroup or something like that? Trying to capture clicks on individual features in the GeoJSON layer on that object won't work, because it won't be able to differentiate between the features. Same goes for the handler on the GeoJSON layer, it will fire, but won't know which feature you clicked. The handler in the onEachFeature function will. But i'm assuming you understand by now if your understanding the code/example above.