One of the most mechanical procedures in the mapping practice is called digitizing. Some people already play with Google Earth and do not know that they are already digitizing when they create polylines to mark features like roads, rivers, and other linear features easily identifiable on the map. In Google Earth, you can save it as a part of a kmz or kml file.
The good thing about mapping is that when things fall apart, your map still holds itself together.
Going back to my main topic, lest I infect you with my morbid and depressive lethargy… There are numerous mapping software, and most advanced online geoportals also have that digitizing function it. You need not look far, even Google Earth has that.
What can I say? It’s absolutely absorbing but if you are not into it, it can get boring. I, for one, am feeling very much marooned these last three days. And I found such comfort (I know, geek comfort!) in digitizing everything away. It’s just like playing Candy Crush where you line things up in an array that makes sense. In the case of maps, you just line up the feature as you need it for your analysis.
Usually you will need a basemap or image (technically called raster) to be able to digitize. In ArcGIS 10, you have some maps to choose from:
I’ll choose Open Street Map for this tutorial, since it has that cartoon-ey feel.
The next step involves determining what exactly is it that you want to digitize from the basemap. It can be a line or a polygon. Common line data includes rivers and roads. Polygons includes lots, buildings, blocks, and other imaginable feature on the map that is of interest to you.
I chose Paris as the geographic area of interest. It’s pretty chaotic, the road system in Paris. It’s made of these radial arrondissements. I distinctly remember in college when I took an urban planning subject and one of the books in the library showed a picture of the radial roads in Paris. Despite the artistic look, it served a very big logistic or transport issue. Maybe that’s why the velo or bicycle and walking is more encouraged than driving around this road network.
First, you need a layer and then pinpoint that place you’d like to create a feature out of. In ArcGIS 10, you can go to ArcCatalog, create a new shapefile by right clicking on the white screen on the folder of your choice.
That will prompt a new dialog box that you need to fill out accordingly. I already chose to outline gardens in a polygon shape, so:
You can also choose to edit your coordinate system at this point. Usually I just import the coordinate system from another shapefile I have created previously. If you don’t have that, just find the appropriate coordinate system. If you are a fan of Google Earth, WGS84 is a very popular choice. You can also input manually or do whatever rocks your boat, basically:
Back to the fun part, then. After clicking ok on that dialog box, you’d be able to exit Arc Catalog and go right back to the mapping software to identify that place you want to trace or digitize. In my case here, I chose Jardin des Tuileries, the famous garden for lovers in Paris. 🙂 I may never be able to go to Paris with my humble salary, but I think I can just be content looking at it from a geographical perspective and play with my maps until my final breathing day.
Simply add the shapefile you formed from the previous step:
Then click the Editor toolbar to start editing:
After clicking that, a new sidebar appears on the right for ArcGIS 10 and you can choose your “weapon” of choice at the bottom. I choose Polygon, since I am targeting an octagonal region that won’t fit in a rectangle or circle:
Once you click that, the cursor changes into a plus sign at the drawing area, and you can start clicking at corners, one corner at a time.
After the last corner, double click, and you got yourself a polygon footprint for that shape. 🙂 You can turn off the original basemap you loaded earlier and you will still have the polygon. 🙂
It’s an absorbing hobby, making map features like this. Time flies when you digitize because it never ends, and you never run out of features to play with.
I only hate it when the task accumulates and I am stuck with a hundred roads in a rather redundant or non-exciting place. But honestly, when you want to forget or have a useful diversion, this is a pretty good activity. It won’t require you to think about your life or things if you are having an especially bad day or week. And then, you can just make it more artistic on your end if you want to. You can make the roads color purple or pink, in any style you fancy and in any number you please and you will not get condemned for what you choose. After all, it’s your rules and your style that governs a map that you make.
Shit only happens with your map when you have a horrible machine that hangs or does not have enough video card or RAM specs to boast for it. Anywhere else, it’s a frigging land mine, bad things can happen to you all the time and you cannot do anything about it. You can only control how you respond. Maybe that’s why I love maps so much.
They’re so neutral, so therapeutic, and much easier to handle than, say, people and life decisions. Can I just drown in these maps and fall into an eternal spell of geographical stimulation? Many people like going places, but I’m pretty happy sitting in one place if it means my head won’t run needlessly and if it means that I can just exist peacefully in my own bubble.
Digitizing is almost so Zen, if it were just the only thing in earth that had to matter.