I am looking for an API to return a list of cities, given the current city (may be coordinates) and some specified driving distance. If driving distance is unfeasible, the list of cities within a radius is also acceptable. Any suggestions on what I can use to accomplish this?
I'm not quite sure why you would do something like that, but you have multiple ways to do so.
Easy way:
You need to get an area and create multiple location around your point (or your given city that you would geocode) and then you can use services that give you a multiple reverse geocoding feature like Here Platform does for example. In this way, you would get multiple cities and then you could filter the duplicated entries.
See: https://developer.here.com/rest-apis/documentation/geocoder/topics/request-first-multi-reverse-geocode.html
Complicated way but way more powerful:
Using the Here Platform, you can retrieve Drivetime area (also called isochronous) so based on a location and a duration, you can retrieve the geometry based on the selected transport mode.
See: http://developer.here.com/rest-apis/documentation/enterprise-routing/topics/resource-calculate-isoline.html#resource-calculate-isoline
Based on this geometry, you can create point as explained before or you can use your own database to query on which would contain city geometries for example.
Hope this helps, I know it's only explained and not coded (no code samples here), but it works for sure. I'll try to put more concrete cases but I'm sorry not now.
Related
The project requires us to be able to pin point which state the given geographic coordinate belongs to. These points need not be only in the US.
One possible idea we had was to use PostGIS.
Is it possible to configure PostGIS to give us back such information?
I had a look at http://postgis.net/docs/Reverse_Geocode.html. It seems like it is possible to Reverse Geocode with this, but what we want is slighly different. We want to be able to store all provincial data and be able to tell which country + province the point corresponds to, if any.
How can we achieve this?
We would rather want to have an in house solution than depending on a third party solution like Google API as we need to be able to process a lot of rows of data. Google etc, have a lot of limitations on usage.
You should try https://gis.stackexchange.com/, I'm sure this question has been asked before, but to save you some time here it goes: reverse_geocode may work the way you want to, but you need the data first, so the real question is where to get the geometries from all the countries and its sub-divisions, you can get them here: http://www.gadm.org/ , but this is a shapefile, so you need to use shp2pgsql.
The syntax for shp2pgsql is this:
shp2pgsql -s 4326 gadm_v2.shp new_table_name > new_table_name.sql
And then you can use reverse_geocode.
i'm working on an application that lets users search for trips from point A to point B.
it needs to solve the following use cases:
find trips that go from point A to point B
find trips that start in some other point, but go trough point A to point B
I'm now looking for a database solution that would be best to support such use cases.
For now we are using MongoDB. But i had to figure out a workaround for the first use case and i have a feling that it's not possible to solve the second use case with it.
It seems to me that all the available noSql dbs that support spatial features allow only for one geospatial index on a document,node etc. This is fine for queries like show me all shops in radius of 5km from this point and the like.
So i'm looking for a solution that could solve both use cases. Is there something like that available?
pgRouting could be used, indeed. First solution, that pops into mind: when first user has entered New York and Columbus as source and destination of his trip, perform routing query and store path as PostGIS linestring geometry.
When second user enters From: Pittsburgh To: Columbus into search form, geocode city names to locations and make PostGIS queries, how far are those points (or city boundaries) from first user's route path. If they are close enough and first user drives on suitable direction, they could share car.
Second idea: after first user has entered trip details, perform routing query and store all place names, that are passed by route, into database.
Both solutions could be easily implemented with Postgres+PostGIS+pgRouting. Biggest disadvantage of pgRouting is low speed (it's possible to improve performance by reducing data in routing graph; routing speed is not so important etc). It's also possible to export road data to external files; use some high-speed routing engines (like OSRM, MoNav etc); and, if necessary, write result back to PostGIS. But this requires definitely much more effort.
Also, if you choose to avoid the Database route (no pun intended), you could use GeoTools graphing Java library.
http://docs.geotools.org/latest/userguide/extension/graph/index.html
Here is some example code and data I produced myself to demonstrate how it can be used.
http://usefulpracticalgeoblog.blogspot.ch/2012/09/geotools-routing.html
It is pretty flexible in terms of the spatial data formats that can be used to build the street network graph, and how the results can be outputted.
Then to find if the starting point of trip B is close to the pre-calculated route for Trip A, you could use JTS (Java Topology Suite), which is part of the GeoTools library. Here is an example of the analysis you might use.
https://gis.stackexchange.com/questions/7699/for-a-given-feature-find-the-closest-point-along-a-given-path
Postgresql with postgis and pgrouting. You need nothing else.
Imagine I have a map shape file (.shp) or osm xml, I'm able to see different kind of data from different layers in GIS oriented programs, e.g. ArcGIS, QGIS etc. But how can I get this info programmatically? Is there a specific library for that?
What I'm really looking for is a some kind of method getMapData(longitude, latitude) to get landscape/terrain info (e.g. forest, river, city, highway) in specified location
Thanks in advance for your answers!
It still depends what you want to achieve whether you are better off using raster or vector data.
If your are using your grid to subdivide an area as an array of containers for geographic features, then stick with vector data. To do this, I would create a polygon grid file and intersect it with each of your data layers. You can then add an ID field that represents the cell's location in the array (and hence it's relative position to a known lat/long coordinate - let's say lower left). Alternatively you can use spatial queries to access your data by selecting a polygon in your vector grid file and then finding all the features in your other file that are contained by it.
OTOH, if you want to do some multi-feature analysis based on presence/abscence then you may be better going down the route of raster analysis. My gut feeling from what you have said is that this is what you are trying to achieve but I am still not 100% sure. You would handle this by creating a set of boolean rasters of a suitable resolution and then performing maths operations on the set (add, subtract, average etc - depending on what questions your are asking).
Let's say you are looking at animal migration. Let's say your model assumes that streams, hedges and towns are all obstacles to migration but roads only reduce the chance of an area being crossed. So you convert your obstacles to a value of '1' and NoData to '0' in each case, except roads where you decide to set the value to 0.5. You can then add all your rasters together in one big stack and predict migration routes.
Ok that's a simplistic example but perhaps you can see why we need EVEN more information on what you are wanting to do.
Shapefiles or an osm xml file are just containers that hold geometric shapes. There are plenty of software libraries out there that let you read these files and extract the data. I would recommend looking at GDAL/OGR as a starting point.
A method like getMapData(longitude, latitude) is essentially a search/query function. You need to be a little more specific too, do you want geometries that contain the point, are within a distance of a point, etc?
You could find the map data using a brute force algorithm
for shape in shapefile:
if shape.contains(query_point):
return shape
Or you can use more advanced algorithms/data structures such as RTrees, KDTrees, QuadTrees, etc. The easiest way to get start with querying map data is to load it into a spatial database. I would recommending investigating PostgreSQL+PostGIS and SpatiaLite
You may also like to look at Spatialite and/or PostGIS which are two spatial enabled databses that you could use separately or in conjunction with GDAL/OGR.
I must echo Charles' request that you explain your use-case in more detail because the actual implementation will depend greatly on exactly what you are wanting to achieve. My reading of this is that you may want to convert your data into a series of aligned rasters which you can overlay and treat as a 3 dimensional array.
First find the minimum frequent patterns from the database.
Then divide them into various data types like interval based , binary ,ordinal variables etc and define various distance measures for all the variables.
Finally apply cluster analysis method.
Is this sequence right or am i missing something?
whether you're right or not depends on what you want to do. The general approach that you describe seems to go into the right direction, but you'll never know if your on target until you answer the following questions:
What is your data?
What are trying to find/Which cluster method do you want to use?
From what you describe it seems to me that you want to do 'preprocessing' steps like feature selection and vectorization. Unfortunately, this by itself can be quite challenging. For example, one of the biggest partical problems is the design of a distance function (there's a tremendous amount of research available).
So, please give us more information on your specific target application.
I am looking to calculate the shortest distance between two points inside SQL Server 2008 taking into account land mass only.
I have used the geography data type along with STDistance() to work out point x distance to point y as the crow flies, however this sometimes crosses the sea which i am trying to avoid.
I have also created a polygon around the land mass boundary I am interested in.
I believe that I need to combine these two methods to ensure that STDistance always remains within polygon - unless there is a simpler solution.
Thanks for any advice
Use STIntersects - http://msdn.microsoft.com/en-us/library/bb933899%28v=SQL.105%29.aspx to find out what part of the line is over land.
After reading your comment your requirement makes sense. However I'm pretty sure there are no inbuilt techniques to do this in SQL Server. I'm assuming you are ignoring roads, and taking an as-the-crow-flies approach but over land only.
The only way I can think to do this would be to convert your area into a raster (grid cells) and perform a cost path analysis. You would set the area of sea to have a prohibitively high cost so the algorithm would route around the sea. See this link for description of technique:
http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=cost_path
Otherwise try implementing the algorithm below!
http://bit.ly/ckvciz
There may be other libraries that do this. Alteratively how about using the new Google Directions API between the two cities - you'd get actual road distances then.
http://code.google.com/apis/maps/documentation/directions/