North River Geographic Systems Inc

Spatial Problem Solving

QGIS

Virtual Layers and Bike Data

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To badly quote a Queen Song, “I like to ride my bicycle”.  I’ve been trying to find new spots to ride. Of course being me I’m always debating things I can map while I’m out doing something.

This weekend I decided to map the Bike Share Program. It was raining so I went with a combination of windshield survey, bike riding, and internet searches to locate the Chattanooga’s Bike Share locations. I have a long standing history of being wrong about everything. When the bike share program started back in 2012 I shrugged and went “this won’t work” and 6 years later we’re got 40ish stations (I counted 40 and the internet tells me 41) and over 400 bikes. All the bike shares have a printed map and Chattanooga’s open data portal has a CSV of old bike locations.

Here are the 40 bike share locations in Chattanooga. I’m hoping to stick this in OSM and on the Open Data Site for Chattanooga.

OpenStreetMap Chattanooga

I had read about Anita Graser’s Flow maps recently.  One thing I notice when I’m out is how many places I see these bikes. Where do people come from and where do they go? Digging around on Chattanooga’s Open Data portal I found travel information that was slightly out of date but provided enough information to make this fun. The data gave me two things I needed: bike check-out locations and check-in locations. I know now people leave from Point A and end up at Point B.

Lets create a virtual layer from the table of information and the point layer. Trips being the table and Locations being the points:

SELECT StartStationID, EndStationID,
make_line(a.geometry, b.geometry)
FROM trips
JOIN locations a ON trips.StartStationID = a.id
JOIN locations b ON trips.EndStationID = b.id
WHERE a.id != b.id

I created what I can only describe as “hub lines” of the Bike System:

That doesn’t really tell me anything. It does show me the power of a virtual layer. A virtual layer is an area of QGIS I’ve not touched much – but in short it’s code  tossed against a dataset and that code creates a new layer in QGIS. In this case I’m using functions in QGIS with some SQL code to render the lines. The lines act like physical data.

I refined the code a bit to only show one bike share. So where do people go that leave from the “main” spot (1299) at Outdoor Chattanooga?

Now that we’ve got fewer lines, things are more interesting. First off I don’t have data for all the stops – hence the dots with no lines. The second part I notice is some people go as far as they can go on a bike. They go to the farthest station. The Bike Share Program is “transportation” now on the same level as a bus but in just a smaller area.

Lets pick at it some more and do this:

Select EndStationID, count(*) from virtual layer group by EndStationID

That tells me the counts of where are people going from 1299. Not surprisingly from this location the #1 destination is this location (1299). People come back to where they rent the bike. The next two stops are “the scenic” bike share at 1319 and the bike share that connects to the free shuttle program at 1303.

The least used one is unsurprisingly 1329. That one is located not quite near the college campus and not quite near anything useful for day to day living. There’s really no reason to go there unless you’re lost or going to the Walker Theater for a concert. 1329 may be at the highest “spot” in the city or at least close to the highest (i.e. you have to ride uphill to get there from anywhere).

My next big question: Is it all connected with bike lanes? That data doesn’t really exist except within OpenStreetMap…and it’s outdated. It may exist somewhere in the city but I’m not sure where. My next mapping fun is finding a source of bike lanes for the city. I will probably make my own.

So what did we learn?

  1. If you come to Chattanooga use the Bike Share (and wear a Helmet)
  2. Virtual layers are pretty powerful and I really only did one thing – but it was a powerful one thing.
  3. OpenData for your city is your friend. I will most likely hassle someone for an updated CSV for the city bike share program.

Go out and make a map….and ride your bike.

QGIS Leader Lines for Labels

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So way back when…..I was working in a production map shop and I had to make a map of a Nuclear Plant. The fun part being it was all manual. So we would use a lettering machine to place the labels and legend on the enlarged photo. We would manually trace all the features on an overlay.

Flash forward and we’re using ArcINFO and placing annotation and then drawing leader lines pointing to the features on an OrthoPhoto.

Last week and I had the chance to do something I don’t normally get to do: make a cartographic map in QGIS. I needed to make leader/callout lines from the labels back to the polygons. I didn’t want to manually draw in leader lines. Searching led me to two posts:

I ended up running with the kartoza example although both helped me understand how to get this working. So for the not too faint of heart……Here goes. I have some polygons on which I need to “cleanup labels” and leader lines would help in that regard. I could pull the labels away from the very small polygons I have and attach them back with a line.

The key to all of this ais Geometry Generators. The basics are you can use code and expressions in QGIS to draw Geometry. So I’m going to draw leader lines from my label to my polygon with some code (that I copied from Kartoza’s example – Hey to Kartoza). My data is Categorized. So I’m starting off with this:

So I’m going to click on Conservation Easement and add a symbol. The symbol will be a geometry generator. Just as a little background – I’m stacking symbology. So I’m adding another symbol to my yellow symbol by using the plus button on the symbol selector. I’m defining the type as a Geometry Generator and the Geometry Type as a line.

 

So what happens with the code I so skillfully pasted into the symbol selector?

make_line(
closest_point($geometry,
make_point( “auxiliary_storage_labeling_positionx” , “auxiliary_storage_labeling_positiony” )),
make_point( “auxiliary_storage_labeling_positionx” , “auxiliary_storage_labeling_positiony” )
)

The code says make a line using the closest point on the polygon and anchor it with the location of the label. Now something happens when I use the label toolbar to move my labels away from the polygons:

Now I have leader or callout lines back to my polygon. I’ll need to add a geometry generator to each category to give me lines for every category. The picky side of me is thinking for 100% control I should manually draw them in (but I’m not). If you read Kartoza’s post they have a more elegant final solution to deal with lines running over your labels. Looking at this now I need to move 210 back to the center of it’s polygon since it’s drawing the leader line under the polygon.Overall – Not bad.

 

FOSS4GNA 2019 – The Short Review

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I tend to spend probably more effort than I should telling people “Go to a FOSS4G Meeting”.

I made my……(think..think… 2013, 2015, 2016, 2017, 2018, 2019) fifth North American Event. Six if you count Boston – but that was International but lets count it – so six.

I think this might be a record for me with consecutive conference attendance. I’m a bit burned out on conferences currently. Usually gis conferences are more of the same – except a FOSS4GNA event isn’t. You never know what’s going to happen. If you make enough of these you become part of the group and to be honest – I could sit in a central area and just talk to people for 3 days. Which I did a lot of….more than I will admit. We talk life, projects, and software.

FOSS4GNA tends to skip around the country – this year it was in San Diego. Which was funny because when I said “Hey I’m going to San Diego people would immediately blurt out ‘OMG You’re going to the conference‘”. Well – no. Not that one – I’m going to the fun one. Jeff Johnson hosted at the Marina Village Conference Center. It was actually a better facility than I gave it credit for at first. It was spread out so you had to be outside. What you ended up doing while walking from one talk to another was stopping and going “Hey I’m in Southern California”. You would at some point stop and sit and not worry about things. Jeff had food trucks swinging by the conference center during breaks – you just wander out and get something. Food was plentiful. Every night there was a social of some sort. You get more done at the socials and over food and drink than you do anything else.

I drifted into more LIDAR talks than normal. I’m a bit blown away at PDAL – I don’t use it for work (yet) but I do play around with it in my spare time. The work going into it and the use cases around it are exciting. I’ve been working with Geoserver more and I went to talks on the new releases that are coming.I bounced into a few QGIS talks. I sat and talked to a lot of people – some that I knew and some that I didn’t. It’s nice hearing what people are doing with FOSS4G software and why people are there. I ran into 3 people from the Southeastern US – and that was nice. I’m not alone in this area screaming into the void.

I did my talk on Henry County’s 911 Server and had some great conversations with people after it was over. It’s nice to see other municipalities drifting into the open source software realm.

I enjoy hearing Paul Ramsey’s Keynotes. He tends to look at the economic side of what we do – that’s an important thing for me. Especially because I make my living doing this and I’m always trying to give back. The synopsis of his talk: Open Source Geo is at it’s “Mid Life” with about 20 years of development. At mid life you sit around and look and there’s not much money for FOSS4G development. There’s plenty in implementation because we are all about selling solutions. If you want to check out the slides – here they are.  What if you took your normal maintenance costs from your commercial software and threw it at an Open Source Project? Maybe hired a developer?

So – I know probably not the best conference summary but it’s hard to summarize the people. That’s really my main attraction to this conference. I can walk into a room of 500 and see people I know and miss people that aren’t there. I can catch up with friends – people are the most important part of this whole thing for me.

What about next year? Next year is the international conference in Calgary….

http://2020.foss4g.org/

….and you should go. I’m going to do my best to get there. Why? People. Come join the community of Free and Open Source Software Community. If you missed out on FOSS4GNA 2019 you missed a good time. If you can’t make 2020 in Calgary keep your eyes open for the next FOSS4G-NA in 2021.

 

FOSS4G SE United States – QGIS Meeting

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Here comes about the most abstract thing I’ve done in a while.

I’ve been having meetings centered around FOSS4G Software in the Southeastern US (Knoxville TN – UTK) for the last 2 years. Over the last 2 we’ve had talks ranging from GRASS to LIDAR to SAGA to QGIS and all points in between. We even have a listserve for email.

Now that we are in the third year I want to shake this up a bit. I’m announcing a QGIS centric meeting for October of 2019. I don’t have a firm date because I have no clue who is interested and who isn’t. I can easily take this to Knoxville or Chattanooga – but my worry with a QGIS centric meeting we may attract more than the normal crows which would be a great thing.

So with that I’m probably going to start some chatter on the QGIS-us users list and a few other places but center it on the southeast-us listserve. SO JOIN THAT MAILING LIST TO HELP ME NOT LOSE MORE HAIR.

  • Cost: As cheap as I can make it
  • Location: Somewhere free
  • Who: You
  • Sponsors: I’ll scream your name out
  • Talks: Yes
  • Workshops: Maybe

With that – prepare to see more noise and a possible website crank up – I’ve got enough lead in time so maybe we can make this a grand adventure. If you want to help email me and you can be part of the insanity.


QGIS Class at TNGIC

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So to break the silence and this is something I should have done much sooner – I’ll be at the TN Geographic Information Council Conference holding a QGIS workshop and possibly talking about QGIS and a client’s implementation of QGIS/PostGIS/Geoserver later in the conference.

Anyway – show up for this:http://www.tngic.org/2019-conference.htm#preconferencetraining if you’ve had questions on QGIS and didn’t know what to do or who to ask or anything else – show up.

QGIS – it’s what all the cool kids are doing.

I will even speak some insanity. Don’t tell anyone but I’ll encourage you to show up up for it even if you didn’t sign up for it. Bring a friend. Sneak in. I will tell no one. Seriously. Bring a laptop and I’ll have QGIS and the data and the presentation on a Thumb Drive. We’ll be using Chattanooga data and making this TN/Chattanooga Centric.

I’ll see you there. We’ll have more crazy to talk about once we shut the door so one can hear us.

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