I'm new to ROR and Google Maps. I need to place some markers from locations in Google Maps (having latitudes and longitudes in a database).
The problem is that I need to select some points with some random distance.
In short, I need to select the location and place it in a map, which must have 100 m distance with each and every points.
If the location is within 100 m range with any other points, it can be neglected. I need to place 10 points from database.
Is there any method?
Assuming that you are needing to find points from your database that are at least 100 meters away from all the other points in the database:
This is a fairly simple problem. It can be visualized as an nxn matrix, with the point set as the rows and columns. In Python, comparing all the distances would look like:
selected = []
for pt1 in pts:
inRange = True
for pt2 in pts:
if pt1.distanceTo(pt2) < 100:
inRange = False
break
if inRange:
selected.append(pt1)
This function iterates through the whole list of points. For each point, it checks the distance from the current point to all the other points. If all the other points are outside 100 meters, it adds the point to an array.
For the distance formula, please see the haversine formula here in code form.
Since you did not specify a language in your question, I will let you translate this into whatever language you need. This is just pseudocode, since not enough details were provided to answer your question with actual code.
Also, if I misunderstood your question, you can adapt this algorithm in some way. It is just to provide some ideas.
Related
I am looking for a tool to match GPS coordinates. Attached is a sheet with a list of GPS coordinates.
https://docs.google.com/spreadsheets/d/1pCVlq7BEUBQyST0iRoPcgp_XUhUyOYjAuPQ3mfR5ehU/edit#gid=0
I tried array but I cannot make 1 cell subtract from a column and even if I do it is taking a very long method.
Do you have any suggestion of what I can use?
I ideal situation I’m hoping for is that it checks the list of coordinates and highlight the coordinates that exist more than once, say within 300meters.
I use this formula to calculate distance between 2 points
= 111*SQRT((X1-X2)^2+(Y1-Y2)^2)
Each change in degree of GPS coordinate, corresponds to 111km on geographical scale approx.
Solution
You can check the coordinate points that are closer than a specific distance by creating, in another sheet, a matrix of distances between all the points and by using conditional formatting to highlight the pair of points that are closer than a specific distance.
Steps to achieve this:
Create a new sheet in your Spreadsheet.
In the first cell insert the following formula:
=ARRAYFORMULA(SQRT(POW(INDIRECT("Sheet1!$B"&(COLUMN(B2)))-Sheet1!$B2:$B340,2) + POW(INDIRECT("Sheet1!$C"&(COLUMN(B2)))-Sheet1!$C2:$C340,2)))
Formula explanation : This formula calculates the euclidean distance between two coordinate points. I have used ARRAY FORMULA to automatically calculate the distance between the first point with the rest of the coordinates of your GPS signal. Note that indirect is used so that you can propagate this formula to the rest of the columns. In this case I am testing with 340 coordinate points but you can increase this as you want.
Select the cell where you wrote the formula in and drag it through the columns until you reach your total number of elements. (You can easily check this when the 0s diagonal reaches the last row of values).
Select your whole range (matrix) and head over to Format -> Conditional Formatting and then in the UI in Less or equal than choose the distance you wish to put as the limit.
In this way you will have this distance matrix telling you which intersection points are closer than a specific distance. This is an example image of how it would look like (for distances smaller than 0.4):
Resources used :
ARRAYFORUMLA, POW, INDIRECT, Conditional Formatting
I have a list of Points-of-Interest (e.g. car rest areas).
The user selects the Starting Point and the Ending Point.
This generates a route.
How can I programmatically filter the POIs that are close (e.g. 50 meters distance from the road) that route?
Can Google Maps SDK or OSRM offer this functionality?
Thank you,
Nick
1. You have to find the distance from one POI to the road.
In order to accomplish this, you have to store your road in a mathematical fashion:
You can sample equidistant points of your road and store them in an array (more practical, less precise) and then calculate the distance of the POI from every point in the array, then save the minor result and repeat the whole process for every POIs.
You can store a road in a function (more and more complex, but more precise). Now that you have this function, you can calculate same distance from your POI, take the minimum value and repeat for all POIs.
2. Google Distance Matrix can actually do this
With this Api you can calculate distance till 2500 origins * destinations points.
The result will give you an array of rows, with each row corresponding
to an origin, and each element within that row corresponds to a pairing of the origin with a destination value.
Example of a request:
https://maps.googleapis.com/maps/api/distancematrix/json?units=metric&origins=32.777211,35.021250&destinations=32.778663,35.015757&key=YOURAPIKEY
This is very useful to your goal, because lets you specify more than one points of which calculates distance.
I have a SQL database set of places to which I am assigned coordinates (lat, long). I would like to ask those points that lie within a radius of 5km from my point inside. I wonder how to construct a query in a way that does not collect unnecessary records?
Since you are talking about small distances of about 5 km and we are probably not in the direct vicinity of the north or south pole we can work with an approximated grid system of longitude and latitude values. Each degree in latidude is equivalent to a distance of km_per_lat=6371km*2*pi/360degrees = 111.195km. The distance between two longitudinal lines that are 1 degree apart depends on the actual latitude:
km_per_long=km_per_lat * cos(lat)
For areas here in North Germany (51 degrees north) this value would be around 69.98km.
So, assuming we are interested in small distances around lat0 and long0 we can safely assume that the translation factors for longitudinal and latitudinal angles will stay the same and we can simply apply the formula
SELECT 111.195*sqrt(power(lat-#lat0,2)
+power(cos(pi()/180*#lat0)*(long-#long0),2)) dist_in_km FROM tbl
Since you want to use the formula in the WHERE clause of your select you could use the following:
SELECT * FROM tbl
WHERE 111.195*sqrt(power(lat-#lat0,2)
+power(cos(pi()/180*#lat0)*(long-#long0),2)) < 5
The select statement will work for latitude and longitude values given in degree (in a decimal notation). Because of that we have to convert the value inside the cos() function to radians by multiplying it with pi()/180.
If you have to work with larger distances (>500km) then it is probably better to apply the appropriate distance formula used in navigation like
cos(delta)=cos(lat0)*cos(lat)*cos(long-long0) + sin(lat0)*sin(lat)
After calculating the actual angle delta by applying acos() you simply multiply that value by the earth's radius R = 6371km = 180/pi()*111.195km and you have your desired distance (see here: Wiki: great circle distance)
Update (reply to comment):
Not sure what you intend to do. If there is only one reference position you want to compare against then you can of course precompile your distance calculation a bit like
SELECT #lat0:=51,#long0:=-9; -- assuming a base position of: 51°N 9°E
SELECT #rad:=PI()/180,#fx:=#rad*6371,#fy:=#fx*cos(#rad*#lat0);
Your distance calculation will then simplify to just
SELECT #dist:=sqrt(power(#fx*(lat-#lat0),2)+power(#fy*(long-#long0),2))
with current positions in lat and long (no more cosine functions necessary). It is up to you whether you want to store all incoming positions in the database first or whether you want to do the calculations somewhere outside in Spring, Java or whatever language you are using. The equations are there and easy to use.
I would go with Euklid. dist=sqrt(power(x1-x2,2)+power(y1-y2,2)) . It works everywhere. Maybe you have to add a conversion to the x/y-coordinates, if degrees can't be translated in km that easy.
Than you can go and select everything you like WHERE x IS BETWEEN (x-5) AND (x+5) AND y IS BETWEEN (y-5) AND (y+5) . Now you can check the results with Euklid.
With an optimisation of the result order, you can get better results at first. Maybe there's a way to take Euklid to SQL, too.
I would like to find all points that are within N miles of a given area.
E.g. the area is California: Find all points that are within 50 miles of the border of California (not the middle of California).
When using Google Maps the distance is calculated using 'the middle' of the given location, but I need to calculate the distance using the borders of the given location. The location could be any zip code, city or country.
Could that be done by drawing a polygon using California's coordinates on a map and calculate the distance to location B using the points of the polygon?
Is there a more elegant solution to this? Any ideas?
Thanks!
I'm not sure if I understand your requirements completely, but I will give it a try with different interpretations:
1. You want to filter own map points:
This can be done with any GIS or a own service that offers a call like my_points_in_area(bbox). Bbox means here boundingbox and is the 2x lat/lon pair describing the rectangle around your given centerpoint. If you want to be accurate and really just deliver whats within 100km, you might need to test the distance to the POIs once more, as the rectangle will also include points that are a bit more far away.
2. You want to filter OSM data:
You might use a reverse-geocoding service as Nominatim to get informations about points of interests that are within this distance: http://wiki.openstreetmap.org/wiki/Nominatim
Otherwise import the OSM data using osmosis to a PostGIS DB. AFAIK there is (currently) no DB tool for Oracle: http://wiki.openstreetmap.org/wiki/Oracle
I'm sorry if I missed your question, but then please add more details :)
I am trying to get the current traffic conditions at a particular location. The GTrafficOverlay object mentioned here only provides an overlay on an existing map.
Does anyone know how I can get this data from Google using their API?
It is only theorical, but there is perhaps a way to extract those data using the distancematrix api.
Method
1)
Make a topological road network, with node and edge, something like this:
Each edge will have four attributes: [EDGE_NUMBER;EDGE_SPEED;EDGE_TIME,EDGE_LENGTH]
You can use the openstreetmap data to create this network.
At the begining each edge will have the same road speed, for example 50km/h.
You need to use only the drivelink and delete the other edges. Take also into account that some roads are oneway.
2)
Randomly chose two nodes that are not closer than 5 or 10km
Use the dijsktra shortest path algorithm to calculate the shortest path between this two nodes (the cost = EDGE_TIME). Use your topological network to do that. The output will look like:
NODE = [NODE_23,NODE_44] PATH = [EDGE_3,EDGE_130,EDGE_49,EDGE_39]
Calculate the time needed to drive between the two nodes with the distance matrix api.
Preallocate a matrix A of size N X number_of_edge filled with zero value
Preallocate a matrix B of size 1 X number_of_edge filled with zero value
In the first row of matrix A fill each column (corresponding to each edge) with the length of the edge if the corresponding edge is in the path.
[col_1,col_2,col_3,...,col_39,...,col_49,...,col_130]
[0, 0, len_3,...,len_39,...,len_49,...,len_130] %row 1
In the first row of matrix B put the time calculated with the distance matrix api.
Then select two news node that were not used in the first path and repeat the operation until that there is no node left. (so you will fill the row 2, the row 3...)
Now you can solve the linear equation system: Ax = B where speed = 1/x
Assign the new calculated speed to each edge.
3)
Iterate the point 2) until your calculated speed start to converge.
Comment
I'm not sure that the calculated speed will converge, it will be interesting to test the method.I will try to do that if I got some time.
The distance matrix api don't provide a traveling time more precise than 1 minute, that's why the distance between the pair of node need to be at least 5 or 10 or more km.
Also this method fails to respect the Google's terms of service.
Google does not make available public API for this data.
Yahoo has a feed (example) with traffic conditions -- construction, accidents, and such. A write-up on how to access it is here.
If you want actual road speeds, you will probably need to work with a commercial provider.