Search points located within given distance from a path in mongoDB - mongodb

Question

Below is the biz document, in it address.location is where I saved the coordinates.
{
"_id" : ObjectId("59944c26085e1140d4575393"),
"category" : "place",
"address" : {
"streetAddress" : "19210 Clay Road",
"city" : "Katy",
"zipcode" : "77449",
"state" : "Texas",
"country" : "United States",
"countryCode" : "US",
"locality" : "Katy, TX",
"location" : {
"type" : "Point",
"coordinates" : [
-95.7043599,
29.832139
]
},
"fomattedAddress" : "19210 Clay Rd, Katy, TX 77449"
}
}
With the below logic I calculated the polygon
Coordinate[] coordinates = new Coordinate[] {new Coordinate(-84.529793, 33.961886), new Coordinate( -84.521698, 33.952987),
new Coordinate(-84.517242, 33.944534), new Coordinate(-84.513290, 33.937264), new Coordinate( -84.498865, 33.915202), new Coordinate(-84.529793, 33.961886)};
GeometryFactory geometryFactory = new GeometryFactory();
LinearRing linear = new GeometryFactory().createLinearRing(coordinates);
Polygon polygon = new Polygon(linear, null, geometryFactory);
Coordinate[] polyCoordinates = polygon.getCoordinates();
With the below mongo query I am trying to get the businesses inside the polygon, but I get no results, am i doing somthing wrong please guide me
db.business.find(
{
"address.location.coordinates": {
$geoIntersects: {
$geometry: {
type: "Polygon" ,
coordinates: [
[ [ -84.529793, 33.961886 ], [ -84.521698, 33.952987 ], [ -84.517242, 33.944534 ], [-84.51329, 33.937264] , [ -84.498865, 33.915202 ], [-84.529793, 33.961886] ]
]
}
}
}
}
)

Answer 1

To find all points within certain distance along the route you need to build a poly around the route.
On the image below I assumed the whole route (green) is a straight line for brevity and clarity. Your query is an $or of 3 shapes - blue start and end point circles with radius R, and a red poly that joins both:
Following javascript code https://jsfiddle.net/961kcxr3/ calculates coordinates for a segment using basic flat geometry. This is what you need to do on application level using your language of choice:
const routeCoords [ [ -84.529793, 33.961886 ], [ -84.521698, 33.952987 ], [ -84.517242, 33.944534 ], [-84.51329, 33.937264] , [ -84.498865, 33.915202 ] ] ];
const R = 1000; // 1 km - radius to search within, adjust to your needs
const M = 1/98000; // radius to radians multiplier
const A = routeCoords[0];
const B = routeCoords[4];
const a = Math.atan2(B[0] - A[0], B[1] - A[1]) + Math.PI / 2;
var polyCoords = [
[
A[0] - Math.sin(a) * R * M,
A[1] - Math.cos(a) * R * M
], [
B[0] - Math.sin(a) * R * M,
B[1] - Math.cos(a) * R * M
], [
B[0] + Math.sin(a) * R * M,
B[1] + Math.cos(a) * R * M
], [
A[0] + Math.sin(a) * R * M,
A[1] + Math.cos(a) * R * M
]
];
Which gives you coordinates of the poly:
[
[-84.516182, 33.970903],
[-84.485254, 33.924219],
[-84.512476, 33.906185],
[-84.543404, 33.952869]
]
And the resulting query:
db.business.find(
{ $or: [
{ "address.location.coordinates": {
$geoWithin: {
$geometry: {
type: "Polygon" ,
coordinates: [ [
[-84.516182, 33.970903],
[-84.485254, 33.924219],
[-84.512476, 33.906185],
[-84.543404, 33.952869],
[-84.516182, 33.970903] // the first point to close the poly
] ]
}
},
} },
{ "address.location.coordinates": {
$geoWithin: {
$centerSphere: [ [ -84.529793, 33.961886 ], 1 / 6378.1 ]
}, // 1 km radius, adjust to your needs
} },
{ "address.location.coordinates": {
$geoWithin: {
$centerSphere: [ [ -84.498865, 33.915202 ], 1 / 6378.1 ]
}, // 1 km radius, adjust to your needs
} }
] }
)
The real-life code should calculate polygons and circles for each segment. It can result with quite large query, so be reasonable balancing between accuracy and speed.
Some cases for optimisation:
if length of a segment is significantly less than the radius R you can skip the poly and use 2 or 1 circle for the segment.
if angle a is the same for 2 consecutive segments, you can join the ends and treat them as a single segment the same way I joined 4 segments in the example above