Archive for June 16th, 2014

June 16, 2014

Prep Step 2: Data collection with Garmin GPS unit

GPS Images

The next step of my preparations was to learn how to use a GPS unit to collect data. Although mobile phones now have the same, or perhaps even more, capabilities as a GPS, the one key thing that a GPS device offers is durability and dependability. Not only are GPS waterproof and drop proof, they also take two AA batteries that you can get anywhere, and have a 24 hour battery life. They also don’t require access to mobile internet. All of these qualities make it excellent for use in the developing context. Phones on the other hand are cheaper and more widely available, but are fragile, need to access internet, and have a shorter battery life. I have to think about all of these factors because Beni only has a few hours of electricity per day. The best action to take will be to bring a good amount of both technologies and bring extra things like portable battery chargers and extra batteries. Prep Step 3 will describe my experience using a mobile phone application for data collection.

The first step in using the Garmin device was the most difficult. I had to figure out how to create my own img file to serve as the background map for the Garmin device. This is where the work that I did in JOSM fits into the picture (see Prep Step 1). When I am finished editing the base map of Beni I will upload it and it will be added to the global OSM map. Then I will retrieve it again using a web program that converts a chosen area selection of OSM and e-mails you a link to a downloadable zip file that includes the img file. It can take one or two days to receive the files and because it is a free service they ask for donations. The “gmapsupp.img” file can be downloaded onto the cards of several GPS devices that can then be enabled once the device is turned on. Mission accomplished! All of the Garmin devices will have the same base map for participants to navigate and work with. Because I can’t really test this part of the process with the Beni map, I downloaded the OSM Garmin img file for Cambridge.

The next task was to learn how to use the device to collect data. I discovered that the Garmin device is quite limited in this respect. I thought I would be able to edit existing Points of Interest for example, or be able to rename existing streets. This is not the case; the only thing that the Garmin unit can do is log what are called “tracks” and “waypoints”. Tracks literally mark your journey with a connected trail of points over time that save the coordinates. Tracking can be enabled or disabled and there is an option to have it enabled while it not being visible on the map. I will enable the tracking because anyone editing the map later will need to know where the groups of mappers went in the city to make sure there are no holes in the gathered information. Waypoints are points that can be logged at any time and can be used for the marking of any Points Of Interest (POIs). It can be marked by choosing to save a waypoint where you are standing, or you can toggle the mouse to select a nearby element such as a road or a building. A title can be given to a waypoint as well as a short note, and you can change the icon that represents the waypoint on the map to better express what it is. Originally I had planned for participants to input the POI and street names as the waypoint titles, and use the note category for descriptors such as type or condition, but I realized that it would take a long time to input the names, especially on devices that have to toggle across a keyboard to select individual letters. The best option will be to send out participants in groups that have a GPS user as well as a physical note-taker with a legend that shows what information to include. I am also planning to use a tool called Field Papers that I will talk about in Prep Step 4. After the storage on the device is full or a task is complete, the data can be uploaded to the computer either by USB connection or removing and reading the MicroSD. After the points are transferred they can be cleared from the device to leave space to go out and collect more. The waypoints and tracks from the Garmin device are “gpx” files that can be opened directly in JSOM or QGIS. A program called GPSBabel is handy if using a different brand device where conversion is required.

That’s about it for preparations with the Garmin device. One task I have yet to do is write out a step by step procedure to use for teaching participants how to use the device. Another thing I need to do is figure out how to get my hands on a few more units to bring along without going broke… :P