Routing in QGIS was, as far as I know, always dependent on an available network. Either you had some database which was pgrouting enabled, or you had some network and used this via the roadgraph plugin. I would like to show you, how to do routing and path finding via googlemaps and import the path into QGIS. Big advantage: You don’t even have to think about a network…Current Solutions
My current knowledge of routing possibilities in QGIS is quite limited. I only know these three:
pgrouting is not a routing method. Instead it is an extension for postgresql like postgis. It requires you not only to have access to a postgresql database which you can administrate but also to have a transportation layer. Once you have it imported into the database you can use pgrouting algorithms on this network. Anita Graser covered the whole process in a blog post 2 years ago. pgrouting is probably the most versatile approach regarding routing in QGIS.
pgrouting example from Anita’s blog
roadgraph plugin
The roadgraph plugin makes it a bit easier to work with points and routes. All you need is a local shapefile which serves as a network. Once you have this, the plugin is able to snap o the network, calculate travel times (if you have the data), lengths and the shortest path from one way to another. Keep in mind that we don’t talk about real-life routing as this plugin doesn’t know any traffic lights ;-).points to route
points to route is quite comparable to the roadgraph plugin but offers less more possibilities or outputs. It simply uses a polyline layer as a network and creates routes for a set of input points along the network.Routing using GoogleMaps API
The primary problems on the above mentioned solutions are:
ip install googlemapsOnce you got this, the finding of a direction is quite easy from the python coding in the qgis python console:import googlemapsfrom datetime import datetimenow = datetime.now()gmaps = googlemaps.Client(key="put YOUR key here!")directions_result = gmaps.directions("Dessau, Germany", "Berlin, Germany",mode="driving",departure_time=now)The result is an ugly list of dictionaries. Especially the rout is not given as a pair of nice X-Y coordinates. Instead it is a encoded polyline as Google names it. The good thing: we can handle it!Importing the route into QGIS
First we need to decode the polyline string into X and Y coordinate pairs as this string representing our polyline is damn ugly:
route given by GoogleMaps API in QGIS
Limitations
As the API operates with a key you have some limitations: You can only call the API 2500 times a day and you need to give attribute to the source of the route / vertices what so ever. But I think this is a better burden than keeping your network in a db up-to-date or fetching GB of data as you need a bigger transportation layer…You can download the script here.The post Routing in QGIS … with Google appeared first on Digital Geography.
My current knowledge of routing possibilities in QGIS is quite limited. I only know these three:
- pgrouting
- roadgraph plugin
- points to route
pgrouting is not a routing method. Instead it is an extension for postgresql like postgis. It requires you not only to have access to a postgresql database which you can administrate but also to have a transportation layer. Once you have it imported into the database you can use pgrouting algorithms on this network. Anita Graser covered the whole process in a blog post 2 years ago. pgrouting is probably the most versatile approach regarding routing in QGIS.
pgrouting example from Anita’s blogroadgraph plugin
The roadgraph plugin makes it a bit easier to work with points and routes. All you need is a local shapefile which serves as a network. Once you have this, the plugin is able to snap o the network, calculate travel times (if you have the data), lengths and the shortest path from one way to another. Keep in mind that we don’t talk about real-life routing as this plugin doesn’t know any traffic lights ;-).points to route
points to route is quite comparable to the roadgraph plugin but offers less more possibilities or outputs. It simply uses a polyline layer as a network and creates routes for a set of input points along the network.Routing using GoogleMaps API
The primary problems on the above mentioned solutions are:
- You need a periodic update of your network layer
- acquire a network layer
- prob. install a postgres DB
- log in at the Google dev page.
- Create a new project.
- Choose “Enable an API”.
- Browse for the API and activate the following APIs: Directions API
- Click on Credentials.
- Click Create new Key for a new public key.
- Select “Server Key”.
- Click Create.
ip install googlemapsOnce you got this, the finding of a direction is quite easy from the python coding in the qgis python console:import googlemapsfrom datetime import datetimenow = datetime.now()gmaps = googlemaps.Client(key="put YOUR key here!")directions_result = gmaps.directions("Dessau, Germany", "Berlin, Germany",mode="driving",departure_time=now)The result is an ugly list of dictionaries. Especially the rout is not given as a pair of nice X-Y coordinates. Instead it is a encoded polyline as Google names it. The good thing: we can handle it!Importing the route into QGISFirst we need to decode the polyline string into X and Y coordinate pairs as this string representing our polyline is damn ugly:
u’mak{HixkiAf@_\\bBeIzDqHbQyXzBgOe@uKcG{]_EiJOmDkAoAcMuHiBcDi@aFl@kQpAuWOcRZmHO}@wAeGoU_NmIaGe@qAl@wCdBqIaDaAmFYcTcIeETmFkCaAmB[oC_ExAe[nJiT|BaPbB}Ft@cI~DmIfBiNx@sOj@iNWcL_CwMgGaNcGaUgEmA}FeCs\\EkQeA}G}GeMoEqJwBqJwDeHyDy_@\\aaAhD}`ArDcQvNmYrDgTKiOiJqe@mMcs@}Cqr@iDgM{LgRiEqN{@oMcAuaBaAeqBhEkbBzAqZrPatAxCuTpATpBbC_@lDqAH_SmOyr@yk@kUkX}Qqa@{Qie@cSyg@qN_[iKsNcWgSsImDiuAoe@s{Ase@cTmImUuRaSe\\qTkm@iVir@cJu\\cKol@eVytAcXygAg]}sAsR}f@}mActBif@on@gWy[{KmTmRql@uKu]c\\udAwG_N_JsLoMgNiJkOqHuVcGaa@iF}QgIcOa\\uZuIqNgVws@eJgX{MuXeOgRyS_O{~@sh@sf@cZwRaPq_@u`@a}@msAqQc\\{Mi\\eUug@eq@}fAyPwXoIyQiUmr@oc@gsAyJuSaTuYav@o~@epAg{AsaA{kAyPuUkPu`@yJ_f@eMa{@i^abCgJq]{GiP_Yob@ig@as@yL_XwJm_@iPkiAkIs]cKgW{SuZi|@_aAoRySyb@we@ef@_i@wQoQwQyJuQcEuUOoUdFmR`J}y@la@cI~C{NvCyWAyWqF{d@{KkqAwZ}JeE}FaI{Hi_@yfAsyHcCsa@r@iuCLck@f@mTzBiRhO}w@tHif@\\eNs@uR_F}VmFiVeAuO`AkhAl@qi@|Aco@tBs_@{AoN}GuO_dAkm@kUaNgY}Yan@up@}J_UmH_^w^kmBaFoO{ImOqGsGiNuGyJeAmNDiiAx@gKo@cHcDyF_G_J{P{MiRoGgDsFaAy_@PmSBkHiAac@mUqN_MyFgMeDoOcTevAeCiLgKgWy]mc@au@_{@qGwCcIw@_S`C}ZbEoLdCsE~EsEnIuFpE}G\\uVyDkNmDoIcJ}[oc@op@o}@odA{vAkw@ifAwcA_pAij@ys@_l@ax@i^kh@kBcJ]sOkAmKsB_EgC]}C`@kEwEsFwDuKeAk[gQ}HyBqByACcAMmEbDo@`Do@pD{@L}G}@{_@uAie@mCuaAeBao@n@gCHkHkBmHgIcyClAaEKsE{AiCi@gKiEccB{@_[NqRdBwA~CAYgJ{AuOa@uNnDkAIcBq@mWWsJ{@HkC`@wC^w@@[wEk@oM}A_b@cMs_@’
The directions API has a very special way of providing route information as they encode the polyline. Therefore github user signed0 created a decode function and we will use the script to decode the result.We will concentrate on the overview route which has not all the points of your route but gives a first impression:coord_chunks = [[]]for char in point_str: value = ord(char) - 63 split_after = not (value & 0x20) value &= 0x1F coord_chunks[-1].append(value) if split_after: coord_chunks.append([])del coord_chunks[-1]coords = []for coord_chunk in coord_chunks: coord = 0 for i, chunk in enumerate(coord_chunk): coord |= chunk >= 1 coord /= 100000.0 coords.append(coord)points = []prev_x = 0prev_y = 0for i in xrange(0, len(coords) - 1, 2): if coords == 0 and coords[i + 1] == 0: continue prev_x += coords[i + 1] prev_y += coords points.append((round(prev_x, 6), round(prev_y, 6)))print pointsNow we have a smooth list of coordinates. We will convert this into vertices of a new polyline shapefile:from PyQt4.QtCore import QVariantlayer = QgsVectorLayer('LineString', 'route', "memory") pr = layer.dataProvider() pr.addAttributes([QgsField("attribution", QVariant.String)])layer.updateFields()fet = QgsFeature() seg=[]for i in range(0,len(points)): seg.append(QgsPoint(points[0],points[1])) fet.setGeometry(QgsGeometry.fromPolyline(seg)) fet.setAttributes(["route provided by google maps api"])pr.addFeatures([fet])layer.updateExtents() #update it QgsMapLayerRegistry.instance().addMapLayer(layer)
route given by GoogleMaps API in QGISLimitations
As the API operates with a key you have some limitations: You can only call the API 2500 times a day and you need to give attribute to the source of the route / vertices what so ever. But I think this is a better burden than keeping your network in a db up-to-date or fetching GB of data as you need a bigger transportation layer…You can download the script here.The post Routing in QGIS … with Google appeared first on Digital Geography.