GeoJSON data format fetching from PostgresQL

Question

I am trying to display the GIS data on the Google map using PostgreSQL.

I have few shapefiles, I imported those shapefile into PostgreSQL. Now I am trying to get this data using this query. After running the query I am getting such type of GeoJSON form PostgreSQL I found that the data retrieved from PostgreSQL is not proper format as Google Maps accepted. The data is in another format please see my GeoJSON data:

$query="SELECT ST_AsGeoJSON(ST_Transform(geom, 4326)) AS geom_in_degrees FROM pymble_10 ";

$result = pg_query($db,  $query);

  $finalArray = array();
  $i=0;

while($row=pg_fetch_row($result)){

   print_r($row);
 }

And I am getting output like this :

Array ( [0] =>
{"type":"MultiPolygon","coordinates":[[[[16826527.7094727,-3992350.20318604],[16826530.7548828,-3992351.11029053],[16826532.8928833,-3992352.14691162],[16826534.1887207,-3992353.50750732],[16826535.0958862,-3992355.12738037],[16826535.7437134,-3992356.68231201],[16826535.8084717,-3992357.97821045],[16826535.6140747,-3992359.27398682],[16826534.9663086,-3992360.50512695],[16826534.059082,-3992361.47698975],[16826532.9577026,-3992362.3192749],[16826531.6619263,-3992362.83758545],[16826530.4309082,-3992362.96722412],[16826528.4871216,-3992363.355896],[16826527.2561035,-3992363.6151123],[16826524.145874,-3992364.32788086],[16826521.9431152,-3992365.04058838],[16826520.4528809,-3992365.23492432],[16826518.6386719,-3992364.97570801],[16826517.3428955,-3992363.6151123],[16826516.1118774,-3992361.2177124],[16826516.046875,-3992358.95001221],[16826516.3060913,-3992357.07110596],[16826517.1484985,-3992355.58081055],[16826518.8331299,-3992353.5723877],[16826520.2584839,-3992352.01739502],[16826521.3599243,-3992350.65667725],[16826522.3319092,-3992350.00878906],[16826524.0812988,-3992349.87921143],[16826527.7094727,-3992350.20318604]]]]} )

Answer 1

ST_AsGeoJSON gives you the geometry in GeoJSON format. Google Maps is probably expecting a feature, or a featurecollection.

It should be clear just watching the geojson.org homepage, where you can find a "feature" GeoJSON example.

You can also compare your GeoJSON with the one found in google map's examples https://storage.googleapis.com/maps-devrel/google.json

Regarding the projection problem, if your geom column is already 4326, you don't need to call the transform function. So your query will be SELECT ST_AsGeoJSON(geom) AS geom_in_degrees FROM pymble_10

However, if projections are correctly set, this should not be a problem.

You can check the column projection with select srid from geometry_columns where f_table_name = 'pymble_10'

and you can check the geometry projection with select st_asewkt(geom) from pymble_10