I have a high volume dataset with keys like this:
lat:6.897585,
long:52.785805,
speed:12,
bearing:144
Basically it is a dataset of records of various trips on cars. The data was stored every few seconds during each trip. The main goal of this project is to be able to visualize only u-turns (turn arounds) on a map. But for now, I am trying to at least show the data on specifc roads. For that, I am using Overpass API
With the help of Overpass Turbo, I can get a dataset with all the roads I need.
However, in the dataset, the road's geometry is represented with LineString type.
My question is, How can I get a bounding box(es) of the roads from Overpass API, so later on, I can display events that happened only on the given roads? Or maybe you have a better solution on how to achieve this?
A bounding box wouldn't be very helpful here, as using it to filter your points would show everything that falls within the box (which could include other nearby roads)
It sounds like getting a buffer around a linestring might get you closer, but could still include points that are within the buffer but not on the road you are inspecting.
The smarter way to do this would be to assign each event to a road segment using some logic based on their attributes/properties, so you don't have to depend on a spatial filter.
Related
I've created a base layer and 6 different overlay (Points of Interest) layers for a leaflet map.
The base layer of markers can appear on the map almost anywhere in the world, but I want the POI layers to appear only if they are in the same area (mapBounds) of the base layer. Probably the screen size.
All the data is pulled from a MySQL database and using Ajax I create the various sets of markers from two different tables, base and poi. This much is all done and working, you can see it at https://net-control.us/map2.php. The green and blue markers are from the base table, other markers are currently selected for view by clicking on the appropriate icon in the lower right. The only one active at the moment is 'Fire Station'. But if you zoom out far enough you will see additional fire stations in the Kansas City area, and in Florida. Those sets are not needed.
After the query runs I create a fitBounds variable of the base layer and another poiBounds for the poi layer. But I'm not sure I need the poiBounds. The number of base markers is generally less than 50 for the base query, but if all the poi markers are pulled world wide that number could be very large.
So I'm hoping someone can help me determine a best practice for this kind of scenario and maybe offer up an example of how it should be done. Should I...
1) Download all POIs and not worry about them appearing outside the base bounds layer? Should I inhibit them from showing in the javascript or in the SQL? How?
2) If I inhibit the unwanted points from SQL do I test one POI at a time to see if its included in the base bounds? How? Are there MySQL functions perhaps to work with this kind of data?
I'm fairly new at leaflet maps and would appreciate examples if appropriate.
2) If I inhibit the unwanted points from SQL do I test one POI at a time to see if its included in the base bounds? How? Are there MySQL functions perhaps to work with this kind of data?
You probably want a column of type POINT, a spatial index on such column (which internally is likely to be implemented as an R-Tree), and spatial relation functions on your SQL query to make use of that index.
Start by reading https://dev.mysql.com/doc/refman/8.0/en/spatial-types.html. Take your time, as spatial databases, spatial data types and spatial indices work a bit differently than their non-spatial equivalents.
I try to get the buildings geometry coordinates polygons from features, but i cant seem to find a way for this to work without the javascript method queryRenderedFeatures or SourceFeatures.
This question Getting building information from mapbox api uses the javascript method, but i want something to work with a link, that i can fetch a json from.
I have managed to come close with something like this:
https://api.mapbox.com/v4/mapbox.mapbox-streets-v8/tilequery/27.598505,47.162098.json?radius=30&layers=road,poi_label,building,geometry&access_token=ACCESS_TOKEN_HERE.
But this has a major flaw:
It only returns geometry as a point:
{"type":"FeatureCollection","features":[{"type":"Feature","id":235028771,"geometry":{"type":"Point","coordinates":[27.598497434198464,47.16209573500234],"type":"building"...}}
You can observe that it returns a point even though it is a building.
Is there a way to do this?
The queryRenderedFeatures method DOES return a polygon. Somehow the information reaches the Map object that i query but how can i fetch through an api that info?
What you're trying to do is not possible. Mapbox doesn't provide complete polygon datasets. At best, there are ways of retrieving polygons from vector tilesets (such as query-remote-tiles, which does something similar to TileQuery). But these will only retrieve the part of the polygon within a given vector tile, which may not be what you want. (queryRenderedFeatures has the same issue).
For a project on geospatial data analytics, we are currently extracting road type and speed limit data of certain roads along a track by using Overpass' polygon query (where we define the roads by a buffer zone around them). The problem is that in the case of separate tracks, we can end up with disconnected polygons which often lead to a significant increase in computation time. In this situation, we were wondering how Overpass' polygon query actually works. Does the algorithm actually query only the data inside this polygon/these polygons, or does it query inside a bounding box, after which it filters out the data inside the polygons?
The algorithm checks if nodes are inside the defined polygon, or if a way crosses the polygon. It's not based on bounding boxes as you mentioned.
From your description it's not quite clear why disconnected polygons pose an issue. You should get decent performance with a lz4-based backend and a reasonable number of lat/lon pairs in your (poly: ) filter (the more pairs you provide, the more expensive the computation gets).
BTW: The best approach to tackle this issue would be something I described in this blog post: https://www.openstreetmap.org/user/mmd/diary/42055 - unfortunately, this feature is not yet available in the official branch. If you see some use for it, please upvote here: https://github.com/drolbr/Overpass-API/issues/418
I need a framework which takes a set of latitude longitude points and plots on a world map, grouped by country having the count of points as a marker on each country. Grouping here is the count of latitude longitude points in a country.
And as I drill down into a country, the clustering should change to state based one. And the next level, to districts.
Leaflet marker cluster is something very similar to what I have asked for, but the grouping is based on proximity and it doesn't consider country or state boundaries. That is, they are not region aware.
Regionbound.com has tweaked in some code in the leaflet code for making it region aware,
Sample marker definition:
var marker1 = new L.marker([-37.8, 145], {regions: ["Asia-Pac", "Australia", "VIC", "Melbourne"]} );
But the sample code says, every latitude longitude must be defined along with some extra parameter containing place information.
I could get the place information using reverse geocoding, but reverse geocoding every latitude longitude is time consuming right.
Highmaps provided by Highcharts is one another solution, but there, every country has code which should be assigned a value[count of point coordinates belonging to that country].
But all I have is latitude longitude points, no country or state information.
Thus, I need something which takes only a set of latitude longitude and does clustering based on country, state, district depending on the zoom level.
You have 2 separate needs in your questions:
Map your lat/lng coordinates to appropriate administrative areas. E.g. through the reverse geocoding that you mention.
Display "clusters" on those administrative areas depending on zoom level.
As for point 1, you know that lat/lng points do not say by themselves which administrative area(s) they belong to. So "reverse geocoding every latitude longitude" is a mandatory step. Whether time consuming or not depends on the solution you choose to perform this operation.
If I understand correctly, you would like a "framework" that could do that automatically for you. But frameworks are usually data agnostic, and if they do not have data about boundaries of those administrative areas, they cannot help you.
You may rather look for "services" (like the Mapbox Geocoding API that you mention) or software that would already have such data. It is not time consuming if you can program the lookup (or perform "bulk" operations) and if you are not limited by the requests rate and your amount of points to map (which may be the case with Mapbox).
You could very well set up your own application to perform this mapping:
As for the dataset for administrative areas boundaries, you would probably be interested in links in this post: Are there any free administrative boundaries available as shapefiles? If your points are limited to a few countries, it will be easier for you to find the appropriate data source(s).
Once you have that data, many GIS software should be capable of mapping your lat/lng points to the areas they belong to. This would be mainly for a "one-shot" operation, if your set of points do not change much.
A "web-compatible" alternative would be for example to use Leaflet with point in polygon for Leaflet plugin. You would need your boundaries data converted to GeoJSON format first. Again, GIS software should be capable of doing so, or many online services as well (search for "convert geojson" for example).
A server-side solution would avoid having to manage the entire boundaries data through network and in client browser (if you need to perform the mapping dynamically). I am sure many GIS servers are capable of performing this operation, once they are fed with the boundaries data.
For point 2, once you have completed the above step, I think you would have many options available, including those you mention (RegionBound, Highmaps).
Even with standard mapping libraries (Leaflet, OpenLayers 3), you would just need to build your "clusters" (markers on administrative areas with a number saying how many points are in there), like you have to do with Highmaps anyway for example.
Computing the number of "clustered" point is as easy as filtering your points per area name / code. Then switch the clusters to the desired administrative level when the map zoom changes.
So the key is really to determine first to which areas your points belong to (point 1).
Then a small question would rise about where to place the "cluster" marker:
On centroid of the administrative area? You need the coordinates of that centroid from your data source, or a good algorithm to compute it from the boundaries (good luck on that…).
On "center" of the bounding box of the area? Leaflet can easily compute that: from your area vector shape, you would do myShape.getBounds().getCenter().
On barycentre / centroid of the clustered points? This is what Leaflet.markercluster and RegionBound do (do not know for Highmaps).
Good luck!
I am trying to call OpenStreetMap API:
http://api.openstreetmap.org/api/0.6/map?bbox=43.65,-79.38,43.66,-79.37
It returns no error, but map is empty:
Do you have any ideas why?
thanks
I think for the given request, the empty dataset delivered is actually the correct response.
The API documentation says api/0.6/map returns
All nodes that are inside a given bounding box and any relations that reference them.
All ways that reference at least one node that is inside a given bounding box, any relations that reference them [the ways], and any
nodes outside the bounding box that the ways may reference.
All relations that reference one of the nodes, ways or relations included due to the above rules. (Does not apply recursively, see
explanation below.)
As far as I can see, your bounding box selects a bit of Antarctica. What data did you expect?
I guess, in OSM, Antarctica is just a way, describing its outline (and maybe some research stations somewhere). If you now ask for an area in the middle of nowhere there, there are no data to get. This is because within your bbox there are no nodes. The way for the outline/area of Antarctica is only fetched if at least one of its nodes lies within your bounding box.
PS: If you want a piece of Toronto (with lots of data), swap longitude and latitude values :)
https://wiki.openstreetmap.org/wiki/Download#Construct_a_URL_for_the_HTTP_API
it says the bounding box can only be 0.5 by 0.5 degrees. it also says you might want to try XAPI for such a large area