OpenLayers can handle geojsons in any coordinate system, but a geojson should not specify EPSG:4326 when the coordinates are in another projection. However, the primary reason why that will not load in OpenLayers is the feature ids are null which is invalid, but can be fixed by undefining the ids. Unless you are expecting data off the coast of Nigeria (assuming OpenLayers default EPSG:3857 projection) you will need find out which projection the coordinates are in and diaplay the map or features in that projection.
var geojson = {"type":"FeatureCollection","features":[{"type":"Feature","id":null,"geometry":{"type":"LineString","coordinates":[[698282.236,377375.758],[698289.591,377372.136],[698183.88,377182.298],[698182.72,377197.045],[698282.236,377375.758]]},"crs":{"type":"EPSG","properties":{"code":"4326"}},"geometry_name":"wkb_geometry","properties":{"ogc_fid":"","area_id":null,"building_id":null,"type":null,"area":null,"owner":null,"description":null,"administration":null,"address":null,"property":null,"layer":"Green Area","extendedentity":null,"linetype":null,"entityhandle":null,"text":null,"wkb_geometry":"01020000000500000000FED478544F2541002731087F081741408D972E634F25418195438B70081741295C8FC28F4E254181E92631790517410AD7A3708D4E2541027B142EB405174100FED478544F2541002731087F081741"}},{"type":"Feature","id":null,"geometry":{"type":"LineString","coordinates":[[698289.591,377372.136],[698295.211,377369.369],[698184.767,377171.028],[698183.88,377182.298],[698289.591,377372.136]]},"crs":{"type":"EPSG","properties":{"code":"4326"}},"geometry_name":"wkb_geometry","properties":{"ogc_fid":"","area_id":null,"building_id":null,"type":null,"area":null,"owner":null,"description":null,"administration":null,"address":null,"property":null,"layer":"Green Area","extendedentity":null,"linetype":null,"entityhandle":null,"text":null,"wkb_geometry":"010200000005000000408D972E634F25418195438B700817411E31086C6E4F2541C022DB79650817416039B488914E25414108AC1C4C051741295C8FC28F4E254181E9263179051741408D972E634F25418195438B70081741"}}]};
var features = new ol.format.GeoJSON().readFeatures(geojson);
features.forEach(function(feature){ feature.setId(undefined) });
var map = new ol.Map({
layers: [
new ol.layer.Tile({
source: new ol.source.OSM(),
}),
new ol.layer.Vector({
source: new ol.source.Vector({
features: features
})
})
],
target: 'map',
view: new ol.View({
center: [698282.236, 377375.758],
zoom: 18
})
})
If the coordinates are EPSG:31700 and as the documentation (but not the proj4 definition) suggests the coordinates are in [northing, easting] order this should display the data in the correct location
proj4.defs('EPSG:31700','+proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000 +ellps=krass +towgs84=28,-121,-77,0,0,0,0 +units=m +no_defs');
if (ol.proj.proj4 && ol.proj.proj4.register) { ol.proj.proj4.register(proj4); }
var features = new ol.format.GeoJSON().readFeatures(geojson);
function reverseTransform(coordinates, output, dimensions) {
var dims = dimensions || 2;
for (var i=0; i<coordinates.length; i+=dims) {
var j = coordinates[i];
coordinates[i] = coordinates[i+1];
coordinates[i+1] = j;
}
return coordinates;
}
features.forEach(function(feature){
feature.setId(undefined);
feature.getGeometry().applyTransform(reverseTransform);
feature.getGeometry().transform('EPSG:31700', 'EPSG:3857');
});
var map = new ol.Map({
layers: [
new ol.layer.Tile({
source: new ol.source.OSM(),
}),
new ol.layer.Vector({
source: new ol.source.Vector({
features: features
})
})
],
target: 'map',
view: new ol.View({
center: ol.proj.transform([377375.758, 698282.236], 'EPSG:31700', 'EPSG:3857'),
zoom: 18,
})
});
I attempted to add +axis=neu to the proj4 definition but it had no effect, so instead I added feature.getGeometry().applyTransform(reverseTransform); and centered the map at [377375.758, 698282.236] instead of [698282.236, 377375.758]
