Introduction Geographical information systems

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.title[
# Introduction <br />Geographical information systems
]
.subtitle[
## .f3.i[🌏️️ <br/> ~/GIS/Projection System]
]
.author[
### <strong>Dr. Ankit Deshmukh</strong>
]
.institute[
### Pandit Deendayal Energy University, Gandhinagar
]
.date[
### 19 October 2022
]

---

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# .white["The early days of GIS were very lonely. No one knew what it meant."]
.f2[-Roger Tomlinson, Father of GIS-]

---
# [<svg aria-hidden="true" role="img" viewBox="0 0 576 512" style="height:1em;width:1.12em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:red;overflow:visible;position:relative;"><path d="M384 112v288c0 26.51-21.49 48-48 48h-288c-26.51 0-48-21.49-48-48v-288c0-26.51 21.49-48 48-48h288C362.5 64 384 85.49 384 112zM576 127.5v256.9c0 25.5-29.17 40.39-50.39 25.79L416 334.7V177.3l109.6-75.56C546.9 87.13 576 102.1 576 127.5z"/></svg>](https://www.youtube.com/watch?v=hkUCrTfgaw8) What Did .blue[John Snow] Know About Cholera?

<img src="images/Snow-cholera-map.jpg" class="w-40 br4 dib center">
E. W. Gilbert's version (1958) of John Snow's 1855 map of the Soho cholera outbreak shows the clusters of cholera cases in the London epidemic of 1854

---
# Geographic Information Systems (GIS)

.pull-left[
## The first GIS
- The first GIS design started in the 1960s, by R.F. Tomlinson.
- In 1968, he created the first Canada Geographic Information System
- It's for Canada's Agricultural Research Development Agency (ARDA).

**Geographic information systems arose from activities in four different fields:**

- Cartography
- Computer graphics
- Databases
- Remote sensing.
]
.pull-right[
<img src="images/GIS.png" class="w-100 br4 dib center">
]

---
# Definition of GIS
.f3[A GIS is a computerized information system like any other database, but all the information in a GIS must be linked to a geographic reference.]

- .dark-blue[ESRI also provided a more straightforward definition of GIS as a computer system capable of holding and using data describing places on the earth's surface.]

- .dark-blue[The United States Geological Survey (USGS) defined provided A GIS as a computer hardware and software system designed to collect, manage, analyze and display geographically (spatially) referenced data.]

---
# What can a GIS do?

There are five basic questions that a complete GIS must answer. These are:

1. What exists at a particular location? <br /> 
*Given a geographic reference (eg, lat, long) for a location, the GIS must describe the features of that location.*

1. Where can specific features be found? <br /> 
*This is the converse of the first question. For example, where are the districts with rainfall greater than 500 mm and less than 750 mm?*

1. Trends or What has changed over time? <br /> 
*This involves answering both questions above. For example, at what locations are the crop yields showing declining trends?*

1. What spatial patterns exist? <br /> 
*If an occurrence of a pest is associated with a hypothesized set of conditions of temperature, precipitation, and humidity, where do those conditions exist?*

1. Modelling or What if? <br /> 
*This is a higher level application of GIS and answers questions like what would be the nitrate distribution in groundwater over the area if fertilizer use is doubled?*

---
# How to locate something on earth?
.pull-left[
- A GIS is to be created from maps of different thematic layers (soils, land use, temperature, etc.).

- The maps are in two dimensions, whereas the earth's surface is a 3- dimensional ellipsoid. Every map has a projection and scale.

- To understand how maps are created by projecting the 3-d earth's surface into a 2-d plane of an analog map, we need to understand the georeferencing concepts.
]
.pull-right[
<img src="images/You-are-here-map.jpg" class="w-100 br4 dib center">
]

---
# Creating a map
specifying the 3-dimensional coordinate system that is used for locating points on the earth's surface, that is,

- Geographic Coordinate System (GCS), and 
- Projected Coordinate System,

Projections are used for projecting into two dimensions for creating analog maps.

---
# Geodetic Systems (the earth, geoid, ellipsoid, spheroid and datum)
<img src="images/Picture1.png" class="w-60 br4 dib center">

.f3[.dark-blue[Geodesy:] a branch of applied mathematics concerned with the determination of the size and shape of the earth and the exact positions of points on its surface and with the description of variations of its gravity field.]

---
# The Geoid

- As the density of the planet is inconsistent, gravitational forces pull in or push out the earth’s surface in different places, resulting in a planet that looks more like a lumpy potato than an egg.

- Models that approximate the lumpy potato we call home are called geoids.

- The *'equipotential surface'* that most closely corresponds to mean sea level.

---
# Ellipsoids
- More accurately, the shape of the Earth is an ellipsoid.
- While ellipsoids are round and smooth like spheres, they are not symmetrical when divided in all directions.

---
# Local and Global Ellipsoids
<img src="images/Datum-and-Ellipsoid.png" class="w-80 br4 dib center">

.footnote[ [rashms.com](https://rashms.com/gis/earth-ellipsoid-coordinate-reference-system-crs-projection-epsg-codes-in-gis/) ]

---
# Datum and Spheroid

- A spheroid is a three-dimensional shape created from a two-dimensional ellipse. .red[(WGS84 1984)]
  - spheroid is distinguished from another by the lengths of the semimajor and semiminor axes.

- A spheroid approximates the shape of the earth, a datum defines the position of the spheroid relative to the center of the earth. .red[(WGS 1984)]
--

.footnote[[geo.hunter.cuny.edu](http://www.geo.hunter.cuny.edu/~jochen/GTECH201/Lectures/Lec6concepts/Datums/Components%20of%20a%20datum.htm)]

---
# Process of map making
.pull-left[
- A 3-dimensional coordinate system to locating points on the earth’s surface:

- Geographic Coordinate System (GCS)
  - Projected Coordinate System

- They are used for projecting into two dimensions for creating analogue maps.

]
.pull-right[
![label](https://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Cartesian-coordinate-system.svg/1200px-Cartesian-coordinate-system.svg.png)
]

---
# Geographic Coordinate Systems (GCS)
.b.dark-blue[The geographic coordinate system (GCS) is a spherical or ellipsoidal coordinate system for measuring and communicating positions directly on the Earth as latitude and longitude.]

.pull-left[
**The geodetic latitude** of a point is the angle from the equatorial plane to the vertical direction of a line normal to the reference ellipsoid.

**The geodetic longitude** of a point is the angle between a reference plane and a plane passing through the point, both planes being perpendicular to the equatorial plane.

**The geodetic height** at a point is the distance from the reference ellipsoid to the point in a direction normal to the ellipsoid.

]
.pull-right[
<img src="images/lat-long.png" class="w-70 br4 dib center">
]

---
# Projected Coordinate System
- A projected coordinate system is a flat, two-dimensional surface. 
- A projected coordinate system has constant lengths, angles, and areas across the two dimensions. 
- A projected coordinate system is always based on a geographic coordinate system that is based on a sphere or spheroid.

---
# Projected Coordinate System
Projection is a mathematical transformation used to project the real 3-dimensional spherical surface of the earth in 2-dimensions on a plane sheet of paper.

---
## Depending on the scale and the agreeable tradeoffs with respect to distortions, a specific projection form is chosen.
<img src="images/Tradeoff.png" class="w-100 br4 dib center">

- Different countries have adopted different standard projections at different map scales.

- In India, the polyconic projection is commonly used by Survey of India (SOI).

---
# Georeferencing

Georeferencing is the process of assigning locations to geographical objects within a geographic frame of reference.

<img src="images/Map.jpg" class="w-50 br4 dib center">
.gray.center[An old map of India]

---
# Distortions of map

<img src="images/USmap.jpg" class="w-70 br3 dib center">
.footnote[Source: https://knowwhereconsulting.co.uk/]

---
# Map projections with angular conformity
Maintaining correct angular properties and preservation of angular relationships.

.dark-red[Examples are the Mercator projection (as shown in Fig) and the Lambert Conformal Conic projection.]

---
# Map projections with equal distance
The projection that preserve distances well called equidistant projections.

.red[The Plate Carree Equidistant Cylindrical] (as shown in Fig) and .red[the Equirectangular projection] are two good examples of equidistant projections.

---
# Projections with equal areas
- Equal areas maps are used when calculations of area are required. 
- An equal area projection creates distortions of angular conformity.

**Alber’s equal area, Lambert’s equal area** and **Mollweide Equal Area Cylindrical projections** (as shown in Fig) are types of equal area projections that are often encountered in GIS work.

---
# CRS in Q-GIS

---

# GIS Data Input
.pull-left[
Spatial Data capture can be in two basic formats:

- .red[Raster format:] the reality is represented as grid of cells/pixels. The raster format is based on continuous fields view of reality (photographs, imageries, etc.

- .red[Vector format:] the reality is represented as points lines and areas. The Vector format is based on discrete objects view of reality (analogue maps)

]

.pull-right[
<img src="images/Vec-Ras.png" class="w-110 br3 dib center">
]

In principle, any real world situation can be represented in digital form in both raster and vector formats.

---
# Vector vs. Raster Data
.pull-left[
![label](https://iimagedesign.com/wp-content/uploads/2016/05/Bitmap_VS_SVG.svg_.png)
]

.pull-right[
<img src="images/Comp.jpg" class="w-100 br3 dib center">
]

---
# Vector data type
.pull-left[
- Vector data provide a way to represent real world features within the GIS environment.
- A feature is anything you can see on the landscape.
- A vector feature has its shape represented using geometry. 
- The geometry is made up of one or more interconnected vertices.

-----

.dark-pink[
1. point features,
2. line features and
3. polygon or area features.
]

]
.pull-right[
<img src="images/park.png" class="w-100 br3 dib center">
]

.footnote[read more:: https://docs.qgis.org/2.8/en/docs/gentle_gis_introduction/vector_data.html]

---
# Point, Line, and Polygon features
<img src="images/vectertype.png" class="w-100 br4 dib center">

--
<br /> <br /> 
The most common vector datatype used in GIS are .dark-red.b[Shapefiles]

---
# What are the shapefile files?

.b.dark-pink[Main File (.SHP):] is a mandatory Esri file that gives features their geometry.

.b.dark-pink[dBASE File (.DBF):] is a standard database file used to store attribute data and object IDs. A `.DBF` file is mandatory for shape files. You can open .dbf files in Microsoft Access or Excel.

.b.dark-pink[Projection File (.PRJ):] is an optional file that contains the metadata associated with the shapefiles coordinate and projection system. I

.b.dark-pink[Index File (.SHX):] is a mandatory Esri shape index position file.

.footnote[Source: https://gisgeography.com/arcgis-shapefile-files-types-extensions/]

---
# Attribute data/ Attribute table
<div class="flex"> <div class="w-30 pa2 mr1">
<img src="images/q-ind.png" class="w-100 br1 dib center"> <br />

○  Attribute data are descriptive data of point, line and area features.  <br /> <br />

○ For points, this may be the name of the location, its elevation, etc. <br /> <br /> 
○ For lines attribute data could be the name of a road etc.

</div> <div class="w-70 pa2 mr1">
<img src="images/Att.png" class="w-100 br3 dib center">
</div> </div>

---
# Shapefiles for India  [<svg aria-hidden="true" role="img" viewBox="0 0 512 512" style="height:1em;width:1em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:green;overflow:visible;position:relative;"><path d="M480 352h-133.5l-45.25 45.25C289.2 409.3 273.1 416 256 416s-33.16-6.656-45.25-18.75L165.5 352H32c-17.67 0-32 14.33-32 32v96c0 17.67 14.33 32 32 32h448c17.67 0 32-14.33 32-32v-96C512 366.3 497.7 352 480 352zM432 456c-13.2 0-24-10.8-24-24c0-13.2 10.8-24 24-24s24 10.8 24 24C456 445.2 445.2 456 432 456zM233.4 374.6C239.6 380.9 247.8 384 256 384s16.38-3.125 22.62-9.375l128-128c12.49-12.5 12.49-32.75 0-45.25c-12.5-12.5-32.76-12.5-45.25 0L288 274.8V32c0-17.67-14.33-32-32-32C238.3 0 224 14.33 224 32v242.8L150.6 201.4c-12.49-12.5-32.75-12.5-45.25 0c-12.49 12.5-12.49 32.75 0 45.25L233.4 374.6z"/></svg>](https://1drv.ms/u/s!AhkMSf-s9DI5k4tsmwsWjpuzJiZsDg?e=tSlcct)

---
# Shape file processing

1. Create Shapefiles
  1. Point
  2. Line
  3. Area

1. Attribute table

1. Joins

1. Operations

---

# Pluging in QGIS
**`Plugins > Manage and Install Plugins`**

---

# Download raster
Shuttle Radar Topography Mission (SRTM)SRTM
Link: https://www.earthdata.nasa.gov/sensors/srtm

![](https://www2.jpl.nasa.gov/srtm/images/SRTM_2-24-2016.gif)

---
# Land use and Land cover data
Decadal Land Use and Land Cover Classifications across India, 1985, 1995, 2005

---

# Download SRTM data with .b.blue[SRTM Downloader]
.pull-left[
1. Install Plugin from Plug-in menu.
2. Open SRTM by clicking the SRTM logo.
3. Use OSM map for guide and set the zoom accordingly 
4. Click .red[Set canvas extent] to select area
5. Click download, it will prompt a log in dialogue.
6. Go to https://urs.earthdata.nasa.gov//users/new to create USGS account. 
]
.pull-right[
<img src="images/SRTM.png" class="w-90 br2 dib center">
]

---
# Add map themes with `QuickMapService`

QuickMapServices: Easy to add basemaps

Easy to use list of services and search for finding datasets and basemaps. Please contribute new services via http://qms.nextgis.com! Developed by NextGIS.

---
# Reprojecting a raster

---
# Reprojecting a Vector

---
# Extracting OSM maps with `QuickOSM` plugin
<img src="images/QuickOSM.png" class="w-80 br2 dib center">