Placement of drawn map on Google Maps

Question

On https://delr.dk/nyheder/ i have placed a drawn map of a city. The only way i can place it is by guessing the imagebounds which isn't very exact.

Im initializing the map by the following code:

const fairmap = document.getElementById("firmap");
const tilt = 65;
const heading = 310;
const map = new google.maps.Map(fairmap, {
      zoom: 17,
      center: { lat: 55.23773150087892, lng: 10.531350331799581 },
      heading: heading,
      tilt: tilt,
      mapId: "9e102c6145fa2e82",
      mapTypeControl: false,
      streetViewControl: false
});
const imageBounds = {
      north: 55.24773150087892,
      south: 55.22773150087892,
      east: 10.571350331799581,
      west: 10.511350331799581,
      };

historicalOverlay = new google.maps.GroundOverlay(    
  pathtoimage,
  imageBounds);
historicalOverlay.setMap(map);            
map.fitBounds(historicalOverlay.getBounds());

Is there a way of placing a drawing exactly on Google Map and then extract the imagebounds.