How to understand entities, save, hasChanged

I have using entities and having a bit of trouble understanding them. I am importing ski resort data from a geojson file. All of the 300 ski resorts imported nicely. Now I am testing if there is an UPDATE to the geojson import file or there is a new record (INSERT). My understand is that I can use hasChanged and SAVE (save will detect if update or insert) but I cannot get hasChanged to detect a change. Here is my code.

public function update_aa_winter_sports_points_from_file(){

$file = file_get_contents(WRITEPATH.'upload_fs_data/aa_winter_sports_points.geojson');
$aa_winter_sports_points = json_decode($file); // The json_decode() function is used to decode or convert a JSON object to a PHP object.
// to count the number of ski resorts
$i = 0;

echo 'Numnber of ski resorts: '.count($aa_winter_sports_points->features); echo '</br>';

foreach ($aa_winter_sports_points->features as $aa_winter_sports_point ){

$x = array($aa_winter_sports_point->properties);

// Convert stdClass object to associative array in php
// https://stackoverflow.com/questions/3442...ray-in-php
$new_OsmSkiResort = json_decode(json_encode($x[0]), TRUE);

// get the id of the ski resort
$id = ($new_OsmSkiResort['id']);
echo $id.'</br>';

$original_OsmSkiResort = $this->OsmSkiResortModel->find($id);

$OsmSkiResort = new \App\Entities\OsmSkiResortEntity();

$OsmSkiResort->fill($new_OsmSkiResort);

if ($original_OsmSkiResort){

if (!$original_OsmSkiResort->hasChanged()){
echo "no change on record number ".$i.'</br>';
}

} else {
$y = $this->OsmSkiResortModel->save($OsmSkiResort) ;
echo "save: ".$y.'</br>';
}

$i++;
echo '</pre>';
}

}