This week the Open Cities Dhaka Project begins. The project is supported by the World Bank and involves the collection and open dissemination of building and infrastructure data in the historic old city of Dhaka. The Open Cities team will collect building attributes, water and sanitation data, and cultural sites, data which will enhance urban decision making and inform future risk reduction projects. Dhaka, Bangladesh is one of the most densely populated cities in the world, with over 15 million people, and a growth rate of about four percent per year. The population density is around 45,000 people per square kilometer. That’s nearly double the density of Manhattan, with a tiny fraction of the skyscrapers. The city is divided into 91 wards, and initially three wards at the heart of old Dhaka are targeted for mapping. These wards – numbers 67, 68, and 69 – cover an area of 1.4 square kilometers. We estimate 6,000 – 10,000 buildings in these three wards, but there may be even more. [inline:P1010454-001.JPG=The Core Mapping Team Holding Map of the Three Wards] Thousands of rickshaws bound through the streets of old Dhaka, dodging the multitude of pedestrians and honking cars and CNGs. Houses are built against and on top of one another, and the urban geography changes rapidly. Mapping will be a challenge. [inline:P1010356.JPG=Crowded, Chaotic Streets] The all-star surveying team taking on this task are Master’s students from the Bangladesh University of Engineering and Technology (BUET). A core team of coordinators has already trained twenty surveyors, who will survey using Field Papers and custom survey forms. The past two weeks have been spent learning the mapping process and looking for solutions to some of the difficulties mapping in such a densely populated area. [inline:P1010374.JPG=Surveyors Mapping with Core Team] Some of the key challenges thus far have been:
- Defining a limited number of key attributes to collect
- Printing and scanning Field Papers at a very high zoom level, because of the density of features
- Poor quality satellite imagery in Dhaka
- GPS doesn’t work except on main streets
The poor imagery quality and unreliability of GPS make mapping difficult, but by no means impossible. The core team has worked out a system of mapping block by block, dividing the area into tiny blocks bounded by streets and footpaths. Using Field Papers printed large on A3 paper, the survey teams will then explore and survey each block. This methodology seems to be the best available for mapping this dense area. Over the next two months we hope to see it successful and the mapping of old Dhaka complete.