So you heard about this GIS thing and you thought to yourself that it might be kind of cool to be able to make your own maps.* But then you looked at the software and decided that it’s rather more dense and complicated and esoteric than you’d like, so you decided that maybe you’d pass on making your own maps and instead just use whatever you could find on the Internet.Fair enough, but the truth is that making your own maps really isn’t very hard.* Sure, the software may be a little dense and complicated and esoteric, but so is most every word processor on the market.* But this doesn’t stop any of us from firing up Word and using it to write a letter.* The same goes for email.* How many of you can claim to know more than 2% of the full capabilities of Gmail?* I know I can’t.
GIS software can indeed perform a great many complex and wondrous scientific operations, but a working knowledge of them is not a prerequisite for using the software.* With a little bit of knowledge and the right data, pretty much anyone can make a respectable map.
Which is what we’re going to do.* Relax – I’ll walk you through the process.* It probably won’t hurt at all.
The first order of business is to secure the software we’ll be using.* There are a bunch of good options out there, but for today’s exercise we’ll be using QGIS, because it’s solid and dependable, but also because it’s my personal favorite.* Head on over to their download page and download and install whatever version of the latest release is appropriate for your system (I’ll be using 2.12.3 throughout).* I have chosen the latest release over the LTS (long term support) version because it includes a variety of new features that are well worth having.* Besides – if you decide to stick with this GIS thing you’ll be updating your software on a regular basis.
Once you have installed QGIS, fire it up.* Right off the bat there are a couple things we’ll want to do.* The first is to simply rearrange the UI to suit our purposes.* The UI is completely customizable (and easily so – just click on things and move them around), so it’s a simple matter to arrange things to better suit our own habits.* In time you’ll determine the setup that best suits you – in the meantime I’ll show you the setup that suits me (out of the box, at least).* The next thing we want to do is change the CRS of our project.* When we first fire up QGIS it defaults to EPSG 4326 (also known as WGS 84).* Maps are projected, necessarily so because when mapping we are representing a three-dimensional object (Earth) two-dimensionally.* Therefore we must project a map in order to draw it.* Projecting is inescapably imperfect, therefore every map distorts something in some way.* We use a CRS (co-ordinate reference system) to project a map.* WGS 84 is intended for maps of a global scale, but our map will be on a local scale (in Massachusetts).* Therefore we’ll change the CRS* to a projection that distorts less on our more focused scale.* For this map we’ll use EPSG 26986, NAD 83/Massachusetts Mainland (Meters).* If you want to know more about projections and co-ordinate systems, a great resource can be found here.
Now we need data.* For this map our task will be easy (but don’t get used to it.* Finding appropriate data is usually the hardest part of GIS), as Massachusetts has a wonderful State GIS agency called (you guessed it) MassGIS.* We’re only going to use six datasets for our map, which really isn’t much as these projects go.* It’s still data, though, and it needs to be managed, so let’s talk about that for a minute.
GIS is driven by data.* As such, practitioners tend to amass enormous amounts of data.* Data that must be organized.* Maps are made out of data, and a failure to properly wrangle said data can be crippling.* Where did I put that data from 6 months ago?* Which one of the 14 folders called “Project X” did I put it into?* Or is it somewhere else?* It’s a road dataset, so did I put it in the huge folder called “Roads”?
I didn’t just make these questions up.* They are questions I have actually had to ask myself at earlier, less organized points in my career.* Trust me.* Properly managing data is the single most important part of modern GIS.* As an added bonus, well organized data is easier to back up.* The value of this cannot be overstated.
This is how I do it.* I start with one master folder called simply “Maps” (in Windows you can make this folder a distinct Library.* I strongly advise doing so).* This folder is where I keep everything – data, projects – everything.* The advantage of this is that I simply have to back up my “Maps” folder and I can sleep soundly at night.* The disadvantage is that my “Maps” folder can get pretty damn large (and I don’t even work with Big Data.* If I did I think I would have to store it elsewhere).* Inside my “Maps” folder are two other folders:* “Data” and “Projects”.* My “Projects” folder contains a myriad of folders (usually one per project), as well as a separate folder called “Saves”.* This is where I keep all the ‘Saves’ of projects, whichever software I happen to be using.* This way all my software defaults to the correct location whenever I ask it to open a project.
The “Data” folder gets considerably more complicated.* And personal.* Its contents are more individualized and dependent upon the work most often performed and the types of data needed to do so.* In my case, I work most often (almost exclusively) in Massachusetts.* Because of this, MassGIS is my go-to source for data.* So it just makes sense for me to organize my data in a manner similar to the method MassGIS uses to organize their data.* Much of their data is organized by town, and I follow suit.* My “Data” folder slowly fills with folders named for towns in Massachusetts.* Inside each town’s folder I further separate the data into folders for vector data (points, lines, polygons) and raster data (images, digital elevation models).* MassGIS organizes some of its data differently, and for this data I include separate folders, appropriately labeled.* For instance, I have a folder called “Statewide” for those datasets that encompass the entirety of Massachusetts.
For this project we will be using two statewide datasets and four town datasets (three from one town, one from another).* Start here to get them.
Again, the choices you make will be your own.* I’m just describing how I do it.
First, I scroll down the MassGIS download page until I reach the section titled ‘Transportation’ under the ‘Infrastructure’ heading in the ‘Vector Data’ section.* There I click on ‘Mass DOT Roads’, then ‘Download these layers’.* I then scroll down to ‘Greenfield’ (in the left-hand column) and click on the filename (eotroads_114.zip) to initiate the download.* I download the file to Maps
أكثر...