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How to GIS with Python


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in the so while call this part of GIS and present in the
subtitle a tale of 2 cities was supposed to be about the the city of my university of hosts and the simple but you to China's range I have chosen only to talk about the simple it's the more interesting case anyways but also the subject is a little bit wrong but it was kind of funny OK let's go on
so what we put money honestly
even this is compact additional my to be what how well it's not very important but now working that's always University in the beginning the school of thought also and teaching electronic engineers physics and programming so and parts of
my work is to finish my phd 0 in 1 year's time I have to deliver a lot presentations and doing that is to that in the context of very fond of project called the consensus which is about collected mobile sensing and modelling of emissions from many attractive and in the sense that it has to kind of use to control emissions you are really interested in the 1 is atomic gasses you to the methane and stuff like that and the other of kind of emissions we're interested in are the more polluting all the more more crude toxic pollution coming from countries that don't have recently acceded part to project which are not OK but the idea is that if you ask you to use a special that acts on the mobile phones and then we get the data of our probably a moving around in the cities countries and we can use that they the thing to to make models so the contents of
this talk is like this so that the short introduction to what GIS is I'm not going to go into all of the although there's a lot of decently key ideas and I'm going to just hence on that would look at removed on a couple of education GIS and I think I'm more interested in the application so that's that's my 40 you between and yielding about where we can find data to use on you keep GIS system modifications something about the and tools available some examples and then long ago in its if I have time to talk about my research on on building a transportation models for these OK so yeah let's get on with the what is the well
it's it's it's just as stands for geographical information systems and it's all about man there are that is that it is simple where not just for a moment William on a sphere of the Earth is spherical and we're like 0 maps to be flat 2 dimensional so how do we have to fit a sphere on a on a piece of paper that so that's where all the nitty-gritty
things coming from in the 1st part through projects for the spherical things on on referring into a 2 dimensional and it turns out that there a lot way of different ways to which so projections with itself was these ways have have certain properties which could conclude properties that but there are no projection which can have all the good properties that have some predictions retaining area some reading length and stuff so so depending on your application you only need different kinds of projections but luckily this has mainly been sold In my you know there's there's a database containing 4 thousand different projections and that is a standard way to to to convert from 1 to that to another so if you have a legacy maps you just need to get to know which kind of predicting the map use using and then you can turn the data into a that the map projection that you need and the most but most of the modern maps using this just USC 84 projection and so if if you start a new project and then it might be a good idea to try to use this projection which is constant so that in the greater part of GIS is mainly this project and there's a lot of mathematics and stuff involved in that and it's kind of hard and confusing so I'm just going to come back to someone who knows about it and go on with the the applications so there are quite a lot of different applications for key ideas this is just 1 of the things and this is from then on all the black dots here are other streets less in my area so someone dominion present in the dependences municipality has has to has to keep track of the majority of students have major and that where they have put in all the locations of treatment so that's a way of keeping track of the 2 assets and that's the way that I could think use for planning and they know how many street lamps happened that know where they are and if they have to be serviced or something like that you that you can plan in the many costs you need to seriously plants and in which all it would be a nice thing to do so that's 1 application and as such a set of things that you program in your environment and other weight another esearc check application is is to keep track of where you put down so it's larger underground cable that your electric cables and stuff like that so that you hopefully you can educates contractors so that they they're not ruling anything when they have to take into account the fleet management so this is more dynamic track thing but is still you would like to know where all your taxes constant trucks where they are and where they're going you you need to to put them on the map may be dynamically but still on a map and if you want if you're sitting you would like to have more accurate maps so that you can you can plan for about 4 different so it's and and the rest of the image industrial to see this is where the and work of the residential area the and stuff like that in in in these kinds of matter also need to features are the of of the geography is is he are there are swamps and what kind of what is a crime made up on the specific sites so that that's another way of of putting information into maps that you can use for quality of things and of course routing which the I think it's very important very used nowadays you very used to curious we do it on our smartphones with it in specialized GPS will find us in our constant that like that so that it has been a very successful application of the state and of course we all know what we would call it a GPS receivers because but that decays only gives us position we need to map to actually find a way from 1 point to another and property the fastest 1 also already meant that I mentioned to the city planning but there's a specialized version of stupid which is trapping planning traffic modeling this is where I have done some research in and and and the problem is of course that we we want to plan our cities so that we we get as little congestion as possible in order to fend for or congestion we need to have a model for
whether it's a truck going and when is it going so alright where can
we find data for all formats will lose that's a very important resource control treatment and if you know it but uh I think that it's it might be pondering valued and underused across the world and this is of course very you know you google maps as many that's good but the openstreetmap has this 1st of all it's an open format and you can actually go in and and changed stuff if you want if if you live in the area the of the the building new roads or the closer role or you can actually go in and change that's in your map in the OpenStreetMap and it's very easy to do so so far for researchers I think that's a very important thing that that the data is available and it's all and free to use the of course can use Google Maps forest just for static
maps but I can reuse it forward to getting the features of of the map so that I can see map where the wrote I can't really get the coordinates of these people that's a little a little bit counter that our sources in addition then what we have a new national data centers for a lot of different maps and there's a single quantum environment GIS which has all kinds of strange information about where previous and and where the other depots for toxic weight waste and stuff like that so you can you can you can go there if you want to actually such the mean of this status is also have these very sources some and that can actually be sometimes be a problem because they they tend to be quite old some of these databases and the value can actually risks to have non-standard protection modes and you can it can be quite hot and to to convert these legacy databases to to a more modern project so that you can use the treatment for instance with the old data from from the link between these so that I just wanted to mention I found this database together about where all the cell towers for for mobile phones are in endemic to those of the universe yeah you could find all the nearest cell-tower few new ones that's also there but I think there must be an application for the old OK so uh this is not easy to see that the man on the the power tools are used in most cases is this it's called q got Quantum GIS q this is the very this is of association program with embedded parts interest so you you can make all your scripts in in in parts and I'm sorry about that is that the quality of our thought it's now but maybe you could just make a little demo
here so about it's it's the same image just below the green columns that of like you this is actually all the roads in the simple about 300 sections built in the simple and and this is the only thing that cultures so you can actually see the Bosporus Strait whether there will be about some island still with with some roles so and then there's the mountains with where there are no problems but is this visualization program is actually fast enough to to accommodate this quite a large number of road so you it redraws quite fast so the these the other
tool reliable mention is the park furious it's a very it's a commercial product and which also has an embedded Python interpreter this it seems to be very popular in research that I'm pretty similar other Paris where using our curious but I think that's I found Jia is a bit more approachable from departments and so I want you to do is to use so yeah so in and I'm going to talk a little bit more about tools in the year these are not Paris and Toulouse say there but there are very good binding students so you can you can you can execute through parts and so but that there are not really the the deposed this database with the extensions called isn't PG are quite good and value so the post of course very good SQL database and to the PostGIS extension gives a lot of work on relevance functions to to manipulate a GIS data so I'm not going into the details but because that's that's a whole new talk and unintelligible cost curious that this PG routing extension has been built so that you can you can if you have the means to produce your data into the into the database you can start to find the shortest paths from 1 point to another if you think that this extension of the knowledge through to to all of the GIS conversion from that a lot of different forms not only predictions but also data from that but there are cases the library is available the hearing and and especially the courtyard toward you which can't actually reach almost any relevant format and converted to so most of the other relevant for this very very generic tools but not that hard to use and that all part of bindings for from both OK so I talked about OpenStreetMap I'm just going to show you hopefully so much so
when you all moments treatment there you can see the next of course and something to to be involved in the media can be made recall recognize these uh the river and of then you what is quite hard to see on this With these causes is that there's actually some problems with this man because there is a you can walk like along here and as you can go under the bridge and you can continue this the power here but there's no connection from this British true troops to this part but that's not how to change which
is presented and if you have a lot in the stuff you are presented with
this you and you can then choose to to connect this footpath year so Prince with this and you just have to 2 . but put in a new line analysis putting the metadata as well as the it's time for then have put in that I don't know if it has a name or prepare the surface and stuff like that but there are a lot of new data that you can put in to OpenStreetMap and what when you're satisfied just press stage and then it will be updated to the these so and I want you to to recognize that it is very easy and it's actually could be beneficial for the for following for the for me as a researcher if it's the OpenStreetMap is as correct as possible so I want you to get you to when you noticed something changed in in your local environment please can try to
to go into those treatment and we can take and change each it's very easy and it's very nice when it's what what is correct so let's go back to the presentation the and so now we
come to my war to my stuff the traffic model that has been working with and yeah Of course this might be very boring for you because this is of course my pet so maybe I go into too much detail about this but the reason why we want to have a class traffic model is in we we want to be able to predict how the traffic flows through the network and we want to be able to predict where the contestants are and and and really specific especially we want to predict how if we change the network how would that's how would that the change the flow through that so what have been working with model that that considers how people actually choose where to drive so it's kind of a self much model for for privacy and then in the research it's usually called quoted assignment problem it's hard to assign drivers to different branches in the network and the basic principles are derived from econometrics and it's based on on finding military or excluded brooms and steady states so it's it's kind of like establish a static model so you the trick is you find out what is the demand for for going from 1 place to another and then you try to find the steady state solution for for that network so it's not a dynamic process but it's the but the big problem with is with these kind of models is that that actually a very large number of different possible routes and if you want to make a computer find that the whole people are distributed through all these structure is actually large problems so this is this is a picture of of Copenhagen was essential part of government where it's so at the bottom right we have the 2 main airports and there's a motorway coming down from the north so this is a an assignment to to see how this I was attracted to so through committing area in the morning when people come from the north and I want you don't want to go to the to the airport so the latch half here is the motorways as motorways people work rate around the companion and goes to the airport so well of course most people choose to to go on like that but it as many as more and more people come onto the motorways and it turns out that the traffic flows and then it actually show that there is all ways that are quite as fast and they're going to through the center of public comment which and might not be that most for for for the morning more interest in this and we capacity so but the idea here is that we try to find out how many occurring at each well wrote and when we have an equilibrium everyone would have the same travel time that's the basic idea because then we have what we call a and use the clicker OK so that how do we model conditions well do we we know that that the rows have a capacity there designed to have a certain amount of power and this is the CDA in the bottom here and when we reach the capacity we know that the traffic flows and we model that with this simple power formula so the time it takes to go through the link is given by by the free flow time that's the flow we would normally you would experience referring to all across the on the road and then we have this power function where 1 when the volume the cost of pre-processing the capacity then we it takes longer and longer time this is a very old formula but it have had worked for it is still works and 50 years old like but it gives actually a very good approximation try and we can use the this idea if we know we have a right to run between the origin and destination and we want to assign traffic to the 2 graphs in such a way that the travel time is the same 1 used to and you can find it at the equilibrium point where these two congestion curves cross that's the basic idea that we use different is this the assignment where everyone has the same travel time because if we don't have central travel time we can't we can have a better travel time by choosing an hour but the basic idea thing it's attributable to nationally problems here vertical and so it ties into all these game tree area economic so selfish useless user click on the different terministic populace only articles in in very small networks because you need to consider all possible graphs so that and in even small networks as a lot of different parts around the world and it's not really feasible to do deterministic the user models so people have invented a stochastic methods where you can look at that well that the basic phonation is that instead of being certain that you have the best possible right the shortest time and we can we can we can put in some stochasticity and and we can then people think they have the best products so that there's a there's a bit of uncertainty and in some sense of certainty we can model and we can we can use that to to drive the assignment process so it turns it into since we are looking for the the smallest travel time it's extreme value problem and stochastic and we can then different formulation for the 1 I worked with this past so as not let its where you where to get help on how powerful and looking at what we've done looking at light if the different use the same links terrorists so that the gas is usually pretty important is nice because you can use stochastic methods that but there are still in the problem with the successive user community is that there will be a non-zero probability to use it we're about so this might be a very small probabilities that use stupid rock but it's will it will be there will be calculated so you you you kind of underestimated the good parts of the program so that's not so in the the simple case I have and use data from from the from OpenStreetMap so you can just there's a there's a that's the way that you can actually you could you don't need to have a complete the complete data set you can just pick the what area that you want to data from and then it's a it's compare converted into a typology so that you have a network where everything is connected and the and it's turned into segments instead of the rows so it's it's it's the it but the wrote segments have done that religion was to solve origin-destination pair used to PostgreSQL thing and had implemented a combination of after December institution equilibrium and the stochastic user equilibrium so that we so that I can assign to attract different results and I used to
GIS for the year visualization so and children I think it's kind kind of a nice you you can see on the left-hand side here you can see the health and that means that there is still a direct connection from the due to curious to the PostgreSQL database and I can just point to compute the dearest to my database and and ask it to show all in my solutions and this this is from this is how I have always algorithm has assignment of traffic to 2 different products of course it's the that's multitude of countries I'm trying to to cover so
that was quite a lot okay so in conclusion so the way that I used hazardous to drive all the other tools that are that libraries for doing writing directly in Python but it was actually very easy and fast to use because just I just did that there are many tools and now I am from the In my talk then yeah yeah it's confusing but it's doable I think that's what I mean the conclusion thank you and
that wouldn't need thank you for the from you but if you look at the little theoretical research and traffic congestion but the actually gets of signals from drivers and to do it and my question is mainly because companies get that from the devices like all Google they figured out from from users of you as an independent research would would you get a single well I'm empowerment fair projects and so there will be in this part of the 3 that students 1 should do do the the mobile applications 1 data modeling me and wanted to visualizations so we have we have made this library for a so it's easy to make applications that sent data and we have to make some applications for to get users to use it so there's application called are you the radiation where you can download this application use it for a month and then is there will be a and manage analysis if your traffic pattern is 54 the because and if it is you can borrow for moment that after have given us some data as another protocol to the moment of bicycles to where we but that when the the municipality of learning it's a small town where teacher they want you to bicycle to to work and then they had they ask you use this application which will measure the bond length of the pipe distance and then accumulated through hopefully get to 2 so that they could back to the moon and back that also gives us the data also when there prime in that class so that they have not been several small-scale isn't like that that gives us some data which we which I can use to to extract from and see where people are actually moving and and I get the speed information as well so I can also cases where there is distance so I can use this data to also I could see my my models are correct will questions and this 1 here during the talk I what was she like going to the question organize useful skill for large the list of of flow points geographical points and areas and lines Is there something could directly in Python that I wanted you recommend before I have a few thousands of points that I want to find the closest ones or 2 groups that would library would you recommend to store located like this you have to look at all under look briefly at out which is the size of routing facility here is on not I don't remember the the data format that used for storage but there are you could look at dykstra there would be several implementations of of garch that actually passed on and world finding accuracy and so you could use that thinking on the comments tool OpenStreetMap has it's the truth of the map is a database of geographical they're fully available you have just now do you give them an update to to the set of possible here the of in between the the increasing number also contributors OpenStreetMap and the increased complexity of all the rules you can do you can make a lot of flows for the attributes is somehow sometimes it's a little too much for new users of not inviting them because they all have a lot of things to learn in OpenStreetMap there is a nice feature we women don't have to the design of the Marco problem all about so that the budget is directly on the page and you can just to put the markers anywhere on the map and variety in language there is some change to this this this falls into the top there is always someone just like you or me or anyone else who goes to that area and then looks at this and 6 is that the problem will know all that this little since there had to do with the priorities and case because I noticed that the Robertson my Library found was but it was not working how the taxi-driver and the posture growth and to find out why and it turned out that there was amazing roundabout just pretending that there's also another feature which I think it's a good feature for the OpenStreetMap this they are trying to automatically find problems so for instance if a full power processes and motorway that should not happen to the market with a narrative there's a lot of what semantic features to to find problems so if you are bored you can also look at all of these in your own area you can look for the errors in in in poetry but there's a special map where you all the errors is pointed out to which is the correct if you need to the and and that kind of text book and that's something speaking in clear example being
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Formal Metadata

Title How to GIS with Python
Title of Series EuroPython 2015
Part Number 45
Number of Parts 173
Author Lehmann, Anders
License CC Attribution - NonCommercial - ShareAlike 3.0 Unported:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal and non-commercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor and the work or content is shared also in adapted form only under the conditions of this license.
DOI 10.5446/20073
Publisher EuroPython
Release Date 2015
Language English
Production Place Bilbao, Euskadi, Spain

Content Metadata

Subject Area Information technology
Abstract Anders Lehmann - How to GIS with Python In this talk I will present some tools for working with Geographic Information Systems in Python. Geographic information Systems are widely used for managing geographic (map) data. As an example I will present how to use Open Street Map data, in routing, traffic planning and estimation of pollution emission. For the purpose of the project EcoSense, GPS data from users smartphones are mapped to OSM roads. The map matching algorithm is written in Python and uses data from the database PostgreSQL, with the PostGIS extension. One of the goals of the EcoSense project is to devise methods to improve the estimation of air quality in urban environments.
Keywords EuroPython Conference
EP 2015
EuroPython 2015

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