I'm kind of new to mongodb.
I want to use mongodb's geospatial feature to query locations in a boundary obtained from google maps. It's like withinBox(swLng, swLat, neLng, neLat). But it fails to give me correct results when the map zooms out, as neLng/neLat is less than swLng/swLat. It seems that this is calculated using x > swLng and x < neLng and y > swLat and y < neLat, not taking map projection into account.
So can I achieve the query by withinBox, or I have to adjust coordinates, or I should use near?
As I commented above, when northeast and southwest points cross the international date line, the query will fail as top right's y is smaller than bottom left's y.
If you are using mongodb with php and doctrine, you need make two queries and merge result on the client side like below:
if ($x1 > $x2) {
$qb->field('coordinates')->withinBox(-180, $y1, $x2, $y2);
$result1 = $qb->getQuery()->execute();
$qb->field('coordinates')->withinBox($x1, $y1, 180, $y2);
$result2 = $qb->getQuery()->execute();
$result = $result1->toArray() + $result2->toArray();
} else {
$qb->field('coordinates')->withinBox($x1, $y1, $x2, $y2);
$result = $qb->getQuery()->execute();
$result = $result->toArray();
}
Related
My application collects geolocation point from the user every certain amount of time, I am trying to use these points in order to calculate the distance from the first point through all of the points.
please note that when the user moves in a straight line, the geolocation points do not form a straight line, because the points I collect have a margin of error due to inaccuracy, thus I can't use something like Haversine formula because it will give incorrect value (longer distance than real distance)
and I can't use Google Maps Distance API because it calculates the distance between 2 points only, and it will be so expensive to call it 200 times to calculate distance through all points.
and I want to calculate this value on the server-side because of some security rules I have. so using the google maps SDK in the front end to calculate it is not an option either.
Any idea ...
One option would be to simplify the line, then run the data through the Google Roads API (assuming the travel is on roads), then measure the length of the resulting line (following the roads).
for anyone facing the same problem,I have followed this link
https://developers-dot-devsite-v2-prod.appspot.com/maps/documentation/roads/snap
here is my code in PHP
// snap the collected points from user to the nearest road using google API
$fields = array(
'path' => '60.170880,24.942795|60.170879,24.942796|60.170877,24.942796|60.170902,24.942654',
'key' => '<YOUR_KEY_HERE>'
);
$url = "https://roads.googleapis.com/v1/snapToRoads?" . http_build_query($fields, '', '&');
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url );
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec($ch);
$response = json_decode($response);
$totalDistance = 0;
$previousPoint = null;
foreach ($response->snappedPoints as $pointOnRoad) {
if(!$previousPoint){
$previousPoint = $pointOnRoad;
continue;
}
$totalDistance += getDistance($pointOnRoad->location->latitude, $pointOnRoad->location->longitude,
$previousPoint->location->latitude, $previousPoint->location->longitude);
}
echo $totalDistance;
// calculate distance between 2 geo points
function getDistance($latitude1, $longitude1, $latitude2, $longitude2) {
$earth_radius = 6371;
$dLat = deg2rad($latitude2 - $latitude1);
$dLon = deg2rad($longitude2 - $longitude1);
$a = sin($dLat/2) * sin($dLat/2) + cos(deg2rad($latitude1)) * cos(deg2rad($latitude2)) * sin($dLon/2) * sin($dLon/2);
$c = 2 * asin(sqrt($a));
$d = $earth_radius * $c;
return $d;
}
We are having similar kind of requirement. There are 2 paths and we need to make sure that each node in 1st path (except start and end) are at least 100 KM away from each other of 2nd path.
Can you please share code snippet or logic behind this.
Using Haversine formula in loop will impact performance. So, please suggest some better solution.
I am working on a small MeteorJS app that plots points on a map based on popular areas for work.
I have this:
Template.list.jobs = function() {
if(Session.get('currentIndustryOnet')) {
jobs = Jobs.find({onet: Session.get('currentIndustryOnet')}).fetch();
// Session.set('jobCount', jobs.count());
var cnt = _.groupBy(jobs, 'address');
console.log(cnt);
return Pagination.collection(jobs);
} else {
jobs = Jobs.find()
Session.set('jobCount', jobs.count());
return Pagination.collection(jobs.fetch());
}
}
The cnt variable returns a properly grouped array (the key of the array is an address like Allentown, PA). I have a collection of Cities which have ever city in the USA along with their LAT/LONGs to plot on a Google Map. So I will take the top 100 from the grouped array, find the lat/long in the Cities collection and plot those points on a map.
I am not familiar with working with a groupedBy method to sort the list based on the length and then pull out the key to use as my search.
I'm not 100% certain about the data structure... but assuming jobs have an address field, and you want them sorted by frequency of occurrence and capped, you could do something like this:
var addresses = _.chain(jobs)
.countBy('address')
.pairs()
.sortBy(function(j) {return -j[1];})
.map(function(j) {return j[0];})
.first(100)
.value();
Note there may be a more clever way to use underscore to arrive at this result. Once you have the capped, sorted list of addresses, you can probably get the lat/long values via a find like:
Cities.find({address: {$in: addresses}}).fetch();
With the help of #Dr.Molle answer I learnt to do free hand drawing in Google maps. Now I'm trying to get the polygon drawn within a polygon something like in the below SS
I want to get the polygons marked in yellow and green within the black.
I'm not sure whether this is possible or not. Please shed some light on this issue.
Updates: on further research I learnt about a method called containsLocation(point, polygons) which is used to find whether the given lat/lng point is within the polygon or not.
But sadly there is no default method to check polygons within polygon provided by Google maps :(
You can check if a polygon is within another polygon by looping through each point of the inner polygon and testing if it is contained within the outer polygon using containsLocation().
var isPolygonInsidePolygon = function (innerPolygon, outerPolygon) {
var pointsInside = 0;
var pointsOutside = 0;
innerPolygon.getPath().getArray().map(function (x) {
(google.maps.geometry.poly.containsLocation(x, outerPolygon)) ? pointsInside++ : pointsOutside++;
});
return (pointsOutside > 0) ? false : true;
};
The JavaScript map() function may not work in older browsers, IE8 or lower.
This is a GIS question. Google Maps API isn't really a full-blown GIS. If you want an open-source solution, I suggest loading your yellow and green polygons into a PostGIS database. Then you can query the database.
As an example, you can encode the drawn polygon as a POLYGON object which has the format:
POLYGON((lon lat, lon lat, lon lat, lon lat, ... lon lat))
And then send that to a PHP file from javascript like (you'll wrap this in a $.get() command or similar and return json results:
getParcels.php?bounds=POLYGON((lon lat, lon lat, lon lat, lon lat, ... lon lat))
In the PHP file, query the PostGIS database and return the ids of the yellow and green polygons:
<?php
$pgcon = pg_connect ("dbname=gis user=gisuser connect_timeout=5") or die ( 'Can not connect to PG server' );
if (!$pgcon) {
echo "No connection to GIS database.\n";
}
$bounds = urldecode($_GET["bounds"];
$ewkt = 'SRID=4326;' . $bounds);
$json = ''; // this will contain your output
// Here I am returning the polygon geometry and the parcelID...
$query .= <<<EOD
SELECT
ST_AsGeoJSON(the_geom) as geom,
parid
FROM
parcels
WHERE
ST_Intersects(the_geom, ST_GeomFromEWKT( $1 ));
EOD;
$result = pg_query_params($pgcon, $query, array($ewkt));
if($result) {
$json = '{"type":"FeatureCollection", "features":[';
while($row = pg_fetch_assoc($result)) {
$json .= '{"geometry":' . $row['geom'] . ',';
$json .= '"type":"Feature","properties":{"parid":"' . $row['parid'] . '"}},';
}
$json = substr($json, 0,-1).']}';
}
echo $json;
?>
This will return the parcels that intersect your polygon using the ST_Intersects command in PostGIS.
An alternative implementation working from #chris-smith solution that might be faster, since it doesn't keep looping if it finds an outside point:
function isPolygonInsidePolygon( innerPolygon, outerPolygon ) {
var points = innerPolygon.getPath().getArray();
for( var i = 0; i < points.length; i++ ){
if( ! google.maps.geometry.poly.containsLocation( points[i], outerPolygon) ){
return false;
}
}
return true;
}
I have a ASP.NET website which contains a Google Map. I am using the GoogleMapForASPNet framework made by some clever and helpful individual.
Anywho, I have a problem with centering the map after inserting two pins.
Basically, I am calculating the middle point of the pins and setting that as the Center Point of the map.
Below is my code:
GooglePoint newPoint = new GooglePoint();
double newLat = 0;
double newLong = 0;
if (googlePointA.Latitude > googlePointB.Latitude)
{
newLat = googlePointA.Latitude - googlePointB.Latitude;
newPoint.Latitude = googlePointA.Latitude - newLat;
}
else
{
newLat = googlePointB.Latitude - googlePointA.Latitude;
newPoint.Latitude = googlePointB.Latitude + newLat;
}
if (googlePointA.Longitude > googlePointB.Longitude)
{
newLong = googlePointA.Longitude - googlePointB.Longitude;
newPoint.Longitude = googlePointA.Longitude - newLong;
}
else
{
newLong = googlePointB.Longitude - googlePointA.Longitude;
newPoint.Longitude = googlePointB.Longitude + newLong;
}
GoogleMapForASPNet1.GoogleMapObject.CenterPoint = newPoint;
GoogleMapForASPNet1.GoogleMapObject.ZoomLevel = 8;
It works half and half, but not properly. As in, when I feed different Pins, it doesn't really center the map, but close enough. Or sometimes, the other pin will be off the map but only an inch, which means the map isn't centered at all.
The zoom is static because the pins will always be close by, so there's no need for me to make it dynamic.
Any help is extremely, extremely, extremely appreciated.
Thank you.
The Google Maps API has an object to do that: google.maps.LatLngBounds
Just create a LatLngBounds object, add your pin coordinates to it with the extend() method, then use the map panToBounds(yourBounds) method and you're all set!
I have found many calculations here and some php examples and most are just over my head.
I found this example:
SELECT b.zip_code, b.state,
(3956 * (2 * ASIN(SQRT(
POWER(SIN(((a.lat-b.lat)*0.017453293)/2),2) +
COS(a.lat*0.017453293) *
COS(b.lat*0.017453293) *
POWER(SIN(((a.lng-b.lng)*0.017453293)/2),2))))) AS distance
FROM zips a, zips b
WHERE
a.zip_code = '90210' ## I would use the users submitted value
GROUP BY distance
having distance <= 5; ## I would use the users submitted value
But, I am having trouble understanding how to implement the query with my database.
It looks like that query has all I need.
However, I cannot even find/understand what b.zip_code actually is! (whats the b. and zips a, zips b?)
I also do not need the state in the query.
My mySQL db structure is like this:
ZIP | LAT | LONG
33416 | 26.6654 | -80.0929
I wrote this in attempt to return some kind of results (not based on above query) but, it only kicks out one zip code.
## Just for a test BUT, in reality I desire to SELECT a zip code WHERE ZIP = the users submitted zip code
## not by a submitted lat lon. I left off the $connect var, assume it's there.
my $set1 = (26.6654 - 0.20);
my $set2 = (26.6654 + 0.20);
my $set3 = (-80.0929 - 0.143);
my $set4 = (-80.0929 + 0.143);
my $test123 = $connect->prepare(qq{SELECT `ZIP` FROM `POSTAL`
WHERE `LAT` >= ? AND `LAT` <= ?
AND `LONG` >= ? AND `LONG` <= ?}) or die "$DBI::errstr";
$test123->execute("$set1","$set2","$set3","$set4") or die "$DBI::errstr";
my $cntr;
while(#zip = $test123->fetchrow_array()) {
print qq~$zip[$cntr]~;
push(#zips,$zip[$cntr]);
$cntr++;
}
As you can see, I am quite the novice so, I need some hand holding here with verbose explanation.
So, in Perl, how can I push zip codes into an array from a USER SUBMITTED ZIP CODE and user submitted DISTANCE in miles. Can be a square instead of a circle, not really that critical of a feature. Faster is better.
I'll tackle the small but crucial part of the question:
However, I cannot even find/understand what b.zip_code actually is! (whats the "b." and "zips a, zips b"?)
Basically, the query joins two tables. BUT, both tables being joined are in fact the same table - "zips" (in other words, it joins "zips" table to itself"). Of course, since the rest of the query needs to understand when you are referring to the first copy of the "zips" table and when to the second copy of the "zips" table, you are giving a table alias to each copy - to wit, "a" and "b"'.
So, "b.xxx" means "column xxx from table zips, from the SECOND instance of that table being joined".
I don't see what's wrong with your first query. You have latitude and longitude in your database (if I'm understanding, you're comparing a single entry to all others). You don't need to submit or return the state that's just part of the example. Make the first query work like this:
my $query = "SELECT b.zip_code,
(3956 * (2 * ASIN(SQRT(
POWER(SIN(((a.lat-b.lat)*0.017453293)/2),2) +
COS(a.lat*0.017453293) *
COS(b.lat*0.017453293) *
POWER(SIN(((a.lng-b.lng)*0.017453293)/2),2))))) AS distance
FROM zips a, zips b WHERE
a.zip_code = ?
GROUP BY distance having distance <= ?";
my $sth = $dbh->prepare($query);
$sth->execute( $user_submitted_zip, $user_submitted_distance );
while( my ($zip, $distance) = $sth->fetchrow() ) ) {
# do something
}
This won't be that fast, but if you have a small record set ( less than 30k rows ) it should be fine. If you really want to go faster you should look into a search engine such as Sphinx which will do this for you.
fetchrow_array returns a list of list references, essentially a two-dimensional array, where each row represents a different result from the database query and each column represents a field from the query (in your case, there is only one field, or column, per row).
Calling while ($test123->fetchrow_array()) will cause an infinite loop as your program executes the query over and over again. If the query returns results, then the while condition will be satisfied and the loop will repeat. The usual idiom would be to say something more like for my $row ($test123->fetchrow_array()) { ..., which will only execute the query once and then iterate over the results.
Each result is a list reference, and the zip code you are interested in is in the first (and only) column, so you could accumulate the results in an array like this:
my #zips = (); # for final results
for my $row ($test123->fetchrow_array()) {
push #zips, $row->[0];
}
or even more concisely with Perl's map statement:
my #zips = map { $_->[0] } $test123->fetchrow_array()
which does the same thing.