Tag: app

A screenshot of the splash image seen on users with iPad retina displays in landscape mode. 

To make the Chicago Offline Bike Map, I need bikeways data. I got this from the City of Chicago’s data portal, in GIS shapefile format. It has a good attribute table listing the name of the street the bikeway is on and the bikeway’s class (see below). After several bike lanes had been installed, I asked the City’s data portal operators for an updated shapefile. I got it a month later and found that it wasn’t up-to-date. I probably could have received a shapefile with the current bikeway installations marked, but I didn’t have time to wait: every day delayed was one more day I couldn’t promote my app; I make 70 cents per sale.

Since the bikeway lines were already there, I could simply reclassify the sections that had been changed to an upgraded form of bikeway (for example, Wabash Avenue went from a door zone-style bike lane to a buffered bike lane in 2011). I tried to do this but ran into trouble when the line segment was longer than the bikeway segment that needed to be reclassified (for example, Elston Avenue has varying classifications from Milwaukee Avenue to North Avenue that didn’t match the line segments for that street). I had to divide the bikeway into shorter segments and reclassify them individually.

Enter the Split Features tool. QGIS is short on documentation and I had trouble using this feature. I eventually found the trick after a search that took more time than I expected. Here’s how to cut a line:

1. Select the line using one of the selection tools. I prefer the default one, Select Features, where you have to click on the feature one-by-one. (It’s not required that you select the line, but doing so will ensure you only cut the selected line. If you don’t select the line, you can cut many lines in one go.)
2. Toggle editing on the layer that contains the line you want to cut.
3. Click Edit>Split Features to activate that tool, or find its icon in one the toolbars (which may or may not be shown).
4. Click once near where you want to split the line.
5. Move the cursor across the line you want to split, in the desired split location.
6. When the red line indicating your split is where you desire, press the right-click mouse button.

Your line segment has now been split. A new entry has been added to the attribute table. There are now two entries with duplicate attributes representing that together make up the original line segment, before you split it.

This screenshot shows a red line across a road. The red line indicates where the road will be split. Press the right-click mouse button to tell QGIS to “split now”.

After splitting, open the attribute table to see that you now have two features with identical attributes. 

Copying features in QGIS

A second issue I had when creating new bikeways data was when a bikeway didn’t exist and I couldn’t reclassify it. This was the case on Franklin Boulevard: no bikeway had ever been installed there. I solved this problem by copying the relevant street segments from the Transportation (roads) shapefile and pasted them into the bikeways shapefile. New entries were created in the attribute table but with blank attributes. It was simple to fill in the street name, class, and extents.

Chicago bikeways GIS description

Bikeway classes (TYPE in the dataset) in the City of Chicago data portal are:

1. Existing bike lane
2. Existing marked shared lane
3. Proposed on-street bikeway
4. Recommended bike route
5. Existing trail
6. Proposed off-street trail
7. Access path (to existing trail)
8. Existing cycle track (also known as protected bike lane)
9. Existing buffered bike lane

It remains to be seen if the City will identify the “enhanced marked shared lane” on Wells Street between Wacker Drive and Van Buren street differently than “existing marked shared lane” in the data.