Mongo Map-Reduce: group documents in a certain distance by value - ruby

Question

I'm trying to convert my aggregation query to Map-Reduce one in MongoDB (using Ruby driver). In my original query, I search for elements in a certain distance from a point and then group them by NEIGHBORHOOD value.
Sample document
{
"_id":"5b01a2c77b61e58732920f86",
"YEAR":2004,
"NEIGHBOURHOOD":"Grandview-Woodland",
"LOC":{"type":"Point","coordinates":[-123.067654,49.26773386]}
}
Aggregation query
crime.aggregate([
{ "$geoNear": {
"near": {
"type": "Point",
"coordinates": [ -123.0837633, 49.26980201 ]
},
"query": { "YEAR": 2004 },
"distanceField": "distance",
"minDistance": 10,
"maxDistance": 10000,
"num": 100000,
"spherical": true
}},
{ "$group": {
"_id": "$NEIGHBOURHOOD",
"count": { "$sum": 1 }
}}
])
So the fragment of the output looks like this:
Output
{"_id"=>"Musqueam", "count"=>80}
{"_id"=>"West Point Grey", "count"=>651}
{"_id"=>"Marpole", "count"=>1367}
Now I'm trying to make something like this in MapReduce. In my map function I try to check if documents are in the correct distance (based on the answer to THIS QUESTION) and if so pass them along to reduce function in which they will be counted. But something is not right and I don't get the desired result - count values are too big. What am I doing wrong?
Map function
map = "function() {" +
"var rad_per_deg = Math.PI/180;" +
"var rm = 6371 * 1000;" +
"var dlat_rad = (this.LOC.coordinates[0] - (-123.0837633)) * rad_per_deg;" +
"var dlon_rad = (this.LOC.coordinates[1] - (49.26980201)) * rad_per_deg;" +
"var lat1_rad = -123.0837633 * rad_per_deg;" +
"var lon1_rad = 49.26980201 * rad_per_deg;" +
"var lat2_rad = this.LOC.coordinates[0] * rad_per_deg;" +
"var lon2_rad = this.LOC.coordinates[1] * rad_per_deg;" +
"var a = Math.pow(Math.sin(dlat_rad/2), 2) + Math.cos(lat1_rad) * Math.cos(lat2_rad) * Math.pow(Math.sin(dlon_rad/2), 2);" +
"var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));" +
"if( rm * c < 10000) { " +
" emit(this.NEIGHBOURHOOD, {count: 1});" +
"}" +
"};"
Reduce function
reduce = "function(key, values) { " +
"var sum = 0; " +
"values.forEach(function(f) { " +
" sum += f.count; " +
"}); " +
"return {count: sum};" +
"};"
Query
opts = {
query:{ "YEAR": 2004 },
:out => "results",
:raw => true
}
Output
crime.find().map_reduce(map, reduce, opts)
{"_id"=>"", "value"=>{"count"=>2257.0}}
{"_id"=>"Arbutus Ridge", "value"=>{"count"=>6066.0}}
{"_id"=>"Central Business District", "value"=>{"count"=>110947.0}}