History of GIS

1. 1832 - Early Spatial Analysis in Epidemiology:

- Charles Picquet creates a map in Paris detailing cholera deaths per 1,000 inhabitants.

- Utilizes halftone color gradients for visual representation.

2. 1854 - John Snow's Cholera Outbreak Analysis:

- Epidemiologist John Snow identifies cholera outbreak source in London using spatial analysis.

- Maps casualties' residences and nearby water sources to pinpoint the outbreak's origin.

3. Early 20th Century - Photozincography and Layered Mapping:

- Photozincography development allows maps to be split into layers for vegetation, water, etc.

- Introduction of layers, later a key feature in GIS, for separate printing plates.

4. Mid-20th Century - Computer Facilitation of Cartography:

- Waldo Tobler's 1959 publication details using computers for cartography.

- Computer hardware development, driven by nuclear weapon research, leads to broader mapping applications by early 1960s.

5. 1960 - Canada Geographic Information System (CGIS):

- Roger Tomlinson develops the world's first operational GIS in Ottawa, Canada.

- CGIS used for Canada Land Inventory, incorporating data on soils, agriculture, wildlife, etc.

6. 1964 - Laboratory for Computer Graphics and Spatial Analysis:

- Howard T. Fisher establishes the Laboratory for Computer Graphics and Spatial Analysis at Harvard.

- Develops influential software code and systems distributed worldwide.

7. Late 1970s to Early 1980s - Commercialization of GIS:

- Public domain GIS systems MOSS and GRASS GIS in development.

- Commercial vendors (M&S Computing, ESRI, Intergraph, Bentley Systems, CARIS, ERDAS) emerge with features from CGIS.

8. 1986 - Desktop GIS Emerges:

- Mapping Display and Analysis System (MIDAS), the first desktop GIS, is released.

- Renamed MapInfo for Windows in 1990, marking the shift from research to business.

9. Late 20th Century - Consolidation and Standardization:

- Rapid growth in GIS systems consolidates on a few platforms by the end of the century.

- Users begin exploring GIS data over the Internet, requiring format and transfer standards.

10. 21st Century - Integration with IT and Internet Infrastructure:

- Integration of GIS with IT and Internet technologies like relational databases, cloud computing, SAAS, and mobile computing becomes a major trend.

- Growing number of free, open-source GIS packages customized for specific tasks.

Comments

Accuracy Assessment

Accuracy assessment is the process of checking how correct your classified satellite image is . 👉 After supervised classification, the satellite image is divided into classes like: Water Forest Agriculture Built-up land Barren land But classification is done using computer algorithms, so some areas may be wrongly classified . 👉 Accuracy assessment helps to answer this question: ✔ "How much of my classified map is correct compared to real ground conditions?" Goal The main goal is to: Measure reliability of classified maps Identify classification errors Improve classification results Provide scientific validity to research 👉 Without accuracy assessment, a classified map is not considered scientifically reliable . Reference Data (Ground Truth Data) Reference data is real-world information used to check classification accuracy. It can be collected from: ✔ Field survey using GPS ✔ High-resolution satellite images (Google Earth etc.) ✔ Existing maps or survey reports 🧭 Exampl...

Change Detection

Change detection is the process of finding differences on the Earth's surface over time by comparing satellite images of the same area taken on different dates . After supervised classification , two classified maps (e.g., Year-1 and Year-2) are compared to identify land use / land cover changes . Goal To detect where , what , and how much change has occurred To monitor urban growth, deforestation, floods, agriculture, etc. Basic Concept Forest → Forest = No change Forest → Urban = Change detected Key Terminologies Multi-temporal images : Images of the same area at different times Post-classification comparison : Comparing two classified maps Change matrix : Table showing class-to-class change Change / No-change : Whether land cover remains same or different Main Methods Post-classification comparison – Most common and easy Image differencing – Subtract pixel values Image ratioing – Divide pixel values Deep learning methods – Advanced AI-based detection Examples Agricult...

Landsat 8 Band designation and Band Combination.

Landsat 8 Band designation and Band Combination. Landsat 8-9 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) Bands Wavelength (micrometers) Resolution (meters) Band 1 - Coastal aerosol 0.43-0.45 30 Band 2 - Blue 0.45-0.51 30 Band 3 - Green 0.53-0.59 30 Band 4 - Red 0.64-0.67 30 Band 5 - Near Infrared (NIR) 0.85-0.88 30 Band 6 - SWIR 1 1.57-1.65 30 Band 7 - SWIR 2 2.11-2.29 30 Band 8 - Panchromatic 0.50-0.68 15 Band 9 - Cirrus 1.36-1.38 30 Band 10 - Thermal Infrared (TIRS) 1 10.6-11.19 100 Band 11 - Thermal Infrared (TIRS) 2 11.50-12.51 100 Vineesh V Assistant Professor of Geography, Directorate of Education, Government of Kerala. https://www.facebook.com/Applied.Geography http://geogisgeo.blogspot.com

Landsat band composition

Short-Wave Infrared (7, 6 4) The short-wave infrared band combination uses SWIR-2 (7), SWIR-1 (6), and red (4). This composite displays vegetation in shades of green. While darker shades of green indicate denser vegetation, sparse vegetation has lighter shades. Urban areas are blue and soils have various shades of brown. Agriculture (6, 5, 2) This band combination uses SWIR-1 (6), near-infrared (5), and blue (2). It's commonly used for crop monitoring because of the use of short-wave and near-infrared. Healthy vegetation appears dark green. But bare earth has a magenta hue. Geology (7, 6, 2) The geology band combination uses SWIR-2 (7), SWIR-1 (6), and blue (2). This band combination is particularly useful for identifying geological formations, lithology features, and faults. Bathymetric (4, 3, 1) The bathymetric band combination (4,3,1) uses the red (4), green (3), and coastal bands to peak into water. The coastal band is useful in coastal, bathymetric, and aerosol studies because...

Geographic phenomena fields objects boundaries.

In geography, geographic phenomena refer to features or processes that can be observed and studied on Earth's surface. These phenomena can be classified into three main categories: fields , objects , and boundaries . Each category has distinct characteristics, representations, and applications in Geographic Information Systems (GIS). 1. Fields A field represents continuous, spatially varying data where a value is present at every location within the study area. It describes conditions that exist across a geographic area. Characteristics : Continuity : Fields have no discrete boundaries; the data is continuous. Gradual Variability : The values of a field change gradually across space. Representation : Typically modeled using raster data in GIS, where a grid structure assigns a value (e.g., temperature or elevation) to each cell. Examples : Temperature Map : Shows temperature variation across a region. Rainfall Distribution : Displays rainfall levels over a large g...

Vineesh V, Geography

Search This Blog