Raj Bhagat P #Mapper4Life Profile picture
Earth Observer, Civil Engineer Tweets: Data-Driven Decision Making, GIS, Remote Sensing, Water, Urban Dev, Environment Views: Personal Working: WRI India Tamil
N.V.Ramanan Profile picture Chandrasekar Profile picture Guruprakash Ramesh Profile picture 5 added to My Authors
Jul 2 10 tweets 4 min read
Short #Thread:

Though heavy rainfall is the trigger, our construction practices of where and how are the biggest causes behind some of the most devastating landslides that are costing both lives and money for us.

1/n Image shows a relatively well vegetated hill slope in #Manipur in 2009
Jun 11 10 tweets 4 min read
Short #Story of a river, a sea, a fishing village, and a groyne

Satellite image from 2005 shows the delta of Porunai river (Thamirabarani) in Thoothukudi district of Tamil Nadu.

1/n Image The river settled some amount of sand in the sea and close to the mouths the sea was shallower and with lots of sand.

2/n Image
May 16 12 tweets 4 min read

#Visualization shows ownership of Cars, Bicyle, Two wheelers and also the households that dont own any of these

Why is this critical to know?

Prepared by @PratapVardhan @Stats_of_India
h/t @indiainpixels Before going into the thread, let us clarify about the data. The data is an end product of a survey which surveyed around ~6,40,000 households across India

Data represented in this viz are aggregated at state level so rural-urban or other geo nuances might be hidden

May 3 5 tweets 2 min read
This is a bridge across the #Chambal river near Morena (on the Madhya Pradesh side of the river), massive sand mining operations are happening right below the bridge! So many bridges across India have collapsed because of this activity More images...
Feb 14 22 tweets 8 min read
Story with maps about Vaan Theevu, a small island off the coast of Thoothukudi, Tamil Nadu.

Animation shows how much the Island has changed over last 3 decades. It has been shrinking for a while.

Here's my take on the subject. Please do read this long thread!
1/n 2)Vaan is one of the many islands found off the coast in Gulf of Mannar. The island along with others are now protected areas.

Vaan island is in the shallow continental shelf part of sea. 3 islands existed to south of it but they were all merged/modified for construction of port
Feb 2 18 tweets 7 min read
#Thread: Here are my views on use of satellite images & maps in the Economic survey 2022.

Overall I have a mixed feeling. I am so glad and delighted that a section has been devoted in this manner but I am not happy how certain maps have been presented as they tend to mislead One of the most highlighted map in the survey was that of night lights. It left many wondering whether India actually grew this way. The answer is no and yes. Night lights did increase over the longer period but it is way exaggerated in this map
Jan 21 4 tweets 2 min read
To protect the borders in #Kanniyakumari District, Travancore kindgom under guidance of Capt. Eustachius De Lannoy built South Travancore lines - a series of fortifications in ~1740s between the ocean & mountains & are now in ruins after being overrun by Company troops in 1809 Except Vattakottai fort, all the other sections of the lines are present as bunds or demolished and now used as roads. Some ruins of the bastions and redoubts are still visible in some places.

Google Earth/Maxar Rendition of Vattakottai fort overlooking the sea.
Jan 13 9 tweets 4 min read
India - State of #forest report from Forest Survey is out. If you get news articles (how forest covr increased/decreased), read it with caution. Will write detailed comments later, but some small fun for now:

In ch-13 maps, they have given Shaksgam away! Illegal to publish..
1/n They had some city level maps of forests.. And their statistics depended on boundary files and the file for Mumbai is riddled with gaps between subdivisions. There are white patches in between because someone didnt digitize it properly and these errors creep into stats
Jan 7 12 tweets 7 min read
#Thread of maps on Palayamkottai, now part of #Tirunelveli

As a city,Palayamkottai has a recorded history for more than a thousand years. It reached its zenith during the British era & was called as "Oxford of South India"

My first thread in 2022 is a tribute to #ThoPa Palaymkottai was located in KeelKalaKootram, a revenue division in the east side of Porunai river (now called Thamirabarani). The fort itself was positioned to protect the lush farmlands & was at the intersection of the farmlands & pastures which designed its socio-cultural setup
Dec 27, 2021 5 tweets 2 min read
Time for another short story

A small river/stream existed near Angul #Odisha. The land around it was allotted to JSPL for development... The company thought the course of the river was too disturbing and decided to change the course of the river.
However there were other smaller streams that were draining into it (obviously) & since the new course didnt account it, they started stagnating (marked in white circle)
Dec 5, 2021 9 tweets 4 min read
Short thread of satellite images
Story of a navigational canal that was built with ~12 crore rupees tax payer money in #Ganga riverbed in #Varanasi Uttar Pradesh.

h/t @Indian_Rivers

Before the construction of the canal, this was the river Ganga
1/n In March 2021, the construction started in the river bed where we can see the machines in action. The canal was supposed to be built parallel to the main river but within the bed.

Nov 7, 2021 14 tweets 5 min read
Many parts of #Chennai have been inundated after heavy rains (22 cm) last night. The city like all other in India faces a wide range of issues and it is UNLIKELY to solve any of the urban flooding related problems that it faces within the next 10 years.
Here's why
1/n Image Chennai Metropolitan region (in particular the city corporation) is relatively flat terrain and is very close to sea level. The agricultural activity in the region had prompted construction of thousands of lakes which were shallow and large in area Image
Oct 24, 2021 17 tweets 7 min read
Thread #Haldwani case:
After extreme rainfall in #Uttarakhand, a bridge failed across Gaula river near Haldwani

Rain wasn't sole cause, it just brought d collapse a bit earlier

Himalayan rivers exit mountains & enter plains with great intensity & it is a critical zone It is in this critical section is Haldwani where the Gaula river exits the himalayas and enters plains. Rivers bring huge amount of sediments with them to settle as well as they have high intensity flows during monsoon to erode

Visual shows the location of the bridge that failed
Oct 16, 2021 8 tweets 3 min read
#Thread - #Bengaluru Airport:
What exactly happened in Bengaluru airport that led to the flooding/stagnation a few days before?
My version:

Before the airport, area (marked in white) was in a ridge between 2 valleys, had cropland, quarries, a minor valey, open scrubland
1/n Even after the completion of phase I which was the runway in the northern side and the terminal, the minor valley was not affected significantly as it was all limited to the northern side. One quarry site also remained holding stagnant water.
Aug 18, 2021 19 tweets 10 min read
Viz: #Kaveri river watershed 😍

I would be posting some #maps about the river with finer details in this thread in coming days! Bookmark.. Image FAQ
Data: SRTM
Software: QGIS
Jun 26, 2021 15 tweets 6 min read
#Story of Lakkasandra lake in #Bengaluru

The thread shows the recent history and transformations it went through over time.

#Map shows the location of lake with an approximate boundary of the plot. The waterbody in Lakkasandra might have lost its original applications many decades ago and hence revenue maps (given on the left) shows it as a government land but not specifically as a waterbody. Google Maps however shows the waterbody as it was detected in the early 2000s
May 10, 2021 35 tweets 16 min read
#Elections are supposed to be about electing representations for framing legislations

However the geography behind delimitation which doesnt consider complex socio-economic conditions promote communal polarization leading to deterioration of Democractic values

1/n Understanding Delmitation:

The constituency delimitation is based on population. and for last delineation exercise, 2001 population was used. Average population was calculated to be 270000 people per constituency

#Map shows Population spread in Tamil Nadu
Apr 27, 2021 6 tweets 3 min read
We talk about #DigitalIndia & every other meeting someone would claim that data is the new gold etc. But when it comes to critical data& good quality data, India is far far behind..

Eg: India's open data platform- data.gov.in provides the locations of hospitals Location quality of many of these hospitals are not very accurate and 250 of them are mark outside the country!
The reason being is that they have automated geocoding using Google Maps
Apr 25, 2021 17 tweets 10 min read

I had earlier posted that I am not confident about Covid Nos & few asked explanation

Attaching satellite images where SWIR bands have picked up fire signals in crematoriums(orange colour). In most cases, this is 1st time detected or ten times intensity detected in past Images from NOIDA, Vrindavan, Mathura, Lucknow (Clockwise from left top)

Orangish -red colour is the place of the ghats where these cremations take place
Mar 13, 2021 9 tweets 5 min read
May had been asking me whether Isha encroached forest lands. IMO this is deviating from actual issue. Read full thread

Isha didNOT build on forest dept lands as such but it VIOLATED rules in other ways

Old Satellite image & map show that it was not forest but revenue land Inorder to protect out environment, we had framed laws to secure permissions from necessary authorities. Since it was farmland and since it came under Hill Area Conservation Authority, necessary permissions were to be secured from respective offices
Mar 12, 2021 7 tweets 3 min read
#SaudiArabia #NEOM

WORKERS KINGS Cause It would be insane to have palaces for kings without golf courses in the desert