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Creating a digital replica of Delhi, one step at a time

Creating a digital replica of Delhi, one step at a time
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First Published: Wed, Mar 03 2010. 11 01 PM IST

Tedious groundwork: Harish and Babban, two members of the DSSDI project, use a ground-penetrating radar machine for their mapping work in Priyadarshani Vihar, east Delhi. Ramesh Pathania / Mint
Tedious groundwork: Harish and Babban, two members of the DSSDI project, use a ground-penetrating radar machine for their mapping work in Priyadarshani Vihar, east Delhi. Ramesh Pathania / Mint
Updated: Wed, Mar 03 2010. 11 01 PM IST
New Delhi: Three men led by Siddharth Singh walk slowly through the dirty, narrow warren of lanes that fan out through east Delhi’s Shakarpur area. Two of them push what looks like a sophisticated three-wheeled pram that bristles with an assortment of wires and consoles. The third carries an oversized map on which he regularly puts marks.
Tedious groundwork: Harish and Babban, two members of the DSSDI project, use a ground-penetrating radar machine for their mapping work in Priyadarshani Vihar, east Delhi. Ramesh Pathania / Mint
Their progress is erratic. Every 20m the trio pauses and the pram is wheeled gingerly across the breadth of the lane. Whenever the device passes over an underground pipe, a sinusoidal squiggle appears on its console. There’s a short confabulation and then the team moves on. A trail of curious onlookers gathers behind the team. They whisper among themselves for a bit and then one of them asks the men what they are doing.
In another corner of Delhi, S.K. Sinha navigates the radials of Connaught Place while poised in front of a computer screen. He weaves through the high-rise buildings, each of which is an exact miniature of those on the ground. “Every lamp post, tree and manhole that you see,” says Sinha pointing to the uncannily real graphic on the screen, “is as it is on the ground.”
Sinha and Singh are part of a huge team that has been working round the clock for the last year and a half. They have persistently and methodically looked high and low, counting manholes, walking streets, and probing the ground for pipes and wires. Their progress has been painstaking, but the Delhi State Spatial Data Infrastructure (DSSDI) project, the most ambitious mapping project undertaken in any city in India, is now nearing completion. Like a recalcitrant beast being tamed, Delhi is yielding grudgingly; and its anatomy is gradually emerging from the mess.
The project, a collaboration between the Delhi government and the Survey of India, aims to create a comprehensive 3-dimensional geographical information system (GIS) for Delhi. When it’s done, a digital replica of the city, true to its terrain, and mapping all its overground and underground features will be available. It will come with information on the inhabitants of every structure in the city, land ownership patterns, and geographical data such as terrain profiles and hydrological characteristics.
Major General Girish Kumar of the Survey of India is at the centre of the undertaking. His office in a run-down government complex is festooned with complex charts. “This is not just an academic exercise,” he says pointing to a large diagram. “Based on the data we’ve collected we’re going to create applications for 26 departments of the Delhi government.” Applications on underground pipes and utilities will be used by agencies such as the Delhi Jal Board; land use and occupancy data will be used by the income tax department; and the mapping of electricity poles will come in handy for utilities such as BSES.
For government departments, the benefits are double-edged. They will, for the first time in most cases, have access to comprehensive and detailed civic records. But, as Kumar points out, it will also become more difficult for them to fudge data. Not surprisingly, cooperation from them has been “uneven”.
While the project is using some data from the Survey of India, Census of India and agencies of the Delhi government, most of the work is being done from scratch. “A lot of the existing data was unreliable,” says Kumar. As an example, he mentions the 2001 Census, which put the total number of buildings in the National Capital Territory (NCT) of Delhi at 2.7 million. “In the normal course we’d expect an increase of between 10% and 20% over a decade,” explains Kumar. But as it turns out, DSSDI has already counted 3.4 million buildings, and the total, according to Kumar, is likely to be as high as five million. The census data was clearly inaccurate.
Data with agencies such as the Municipal Corporation of Delhi, or MCD, was even scantier. “They had records of 8 lakh properties, of which half was digital and the other half was on paper,” says Kumar.
Even the 1:25,000 scale (1 centimetre to 250m) maps of the Survey of India weren’t adequate for their purposes.
DSSDI commissioned the Indian Air Force (IAF) to take aerial photographs covering 1,486 sq km of the city on a 1:8,000 scale. Each of these 2,500 photographs, says Sinha, deputy director of the project, overlapped with the ones around it by 60%. When the basic principles of triangulation and some not-so-basic software, was applied to these overlapping images, a “seamless” 3-dimensional layout of the city emerged.
The photographs had given the cartographers most of the detail they were looking for, but they had limitations. “In some cases, buildings clustered close together obscured lanes running between them,” says Sinha. “And in others, lanes that were 3m wide showed up as lines, but smaller ones weren’t visible.”
That’s where the tedious groundwork came in. The photographs were geographically referenced or anchored with the help of existing maps and the 800 global positioning system (GPS) points that were established on the ground. The city was divided into 1,900 squares, each of which had a separate map.
Nearly 1,500 people from the Survey of India and private agencies such as Navayuga Spatial Technologies which had been hired for the project, fanned out across the city, verifying the data, measuring distances from GPS points, and marking features like lanes, lamp posts and manholes which might not have appeared on the photographs. This detailing allowed the maps to be scaled up from the original 1:8,000 to 1:2,000.
After these details had been added, the teams doing the property and underground utility surveys took over. The 400 people in the property survey have been trawling the city listing the inhabitants of every construction “over 2m in height” and taking photographs of buildings. These photographs will be used to create textures, which according to Sinha, will be applied to the 3-dimensional model, making its depictions accurate down to the right colour.
Simultaneously, a team of 100, of which Siddharth Singh is a member, has been doing the survey of underground utilities. Using ground-penetrating radar (GPR) machines, they’ve been trawling the streets of Delhi. The machine Singh uses is relatively simple, but “the massive Terravision GPR machine that we have is being used for the first time in the country,” says Kumar proudly.
It’s been running day and night, moving 5km an hour over every inch of the 18,000km of roads in the Capital, converting the murky network of sewers, cables, water and gas pipes that run through the underbelly of the city into clicks and parabolic curves. These underground features are correlated with those over-ground such as taps and junctions to establish what they carry and which utility company they belong to.
Back in the office of DSSDI, data operators and engineers have been working three shifts a day, six days a week on 110 computer systems to collate and analyse the huge amount of data that is coming from the field.
The project has had its ups and downs. There have been frustrating delays due to rains, general elections and hostility from residents of Delhi who’ve mistaken the team for officials of the MCD. “Delhi is a difficult city to work in,” says Kumar. “There have been times when our teams have been roughed up and have had to be rescued by the police.”
Given the size and complexity of the task, progress has been fast. The survey of New Delhi—north, central and southwest districts—is complete. Work in the remaining five districts is nearing completion. The anatomical model of Delhi that is emerging has, according to Kumar, an astonishing 337 layers, one each for ATMs, banks, parks, trees, hospitals, etc., the assortment of features that make a city.
“It’s the best project in the country,” avers GIS expert I.V. Murali Krishna of Jawaharlal Nehru Technical University, Hyderabad. According to him, the project design takes into account all the complexities of a city like Delhi. “But it will only succeed, if in the long term, government departments use and update the database in coordination,” he says.
Will the project data be freely accessible? “Some of it is going to be linked to the Delhi government website before the (October) Commonwealth Games,” says Kumar. “But we need clearance from the ministry of defence before we do that.” Also to be decided is whether DSSDI will sell data to private companies.
In the meantime, the excitement is building up at the DSSDI office. “This is a dream project for a cartographer,” says Sinha with a gleam in his eye. “It is,” agrees Kumar. “Did you know,” he chuckles, “that there are parts of Delhi which have as many as 200 manholes a square kilometre?”
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First Published: Wed, Mar 03 2010. 11 01 PM IST