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Jannat

Geospatial Researcher
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Jannat Khosla

Geospatial researcher working across GIS, remote sensing, drone photogrammetry and GNSS surveying. Based in Chandigarh, India.

Chandigarh 160015, India

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Jannat Khosla
© 2026 Jannat Khosla — Chandigarh, IndiaDesigned & built by Tanish Mittal
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GIS, remote sensing & field notes.

SEO-friendly, plain-English guides to the satellite imagery, indices and survey workflows I use — written to help students and early-career geospatial analysts.

NDVI Thresholds for Land Cover Classification: What the Numbers MeanLatest
6 Jul 20267 min read

NDVI Thresholds for Land Cover Classification: What the Numbers Mean

Fixed NDVI thresholds borrowed from global studies routinely misclassify Indian land cover because soil background, monsoon phenology, and sensor differences each shift values by 0.1–0.2 or more. This article explains what NDVI actually encodes and how to build a more defensible classification workflow for India's ecologically diverse landscapes.

ndvi thresholdsland cover classificationremote sensing indiavegetation index
RISAT-2B SAR: Bands, Modes and Applications for Indian Users
5 Jul 20267 min

RISAT-2B SAR: Bands, Modes and Applications for Indian Users

RISAT-2B is ISRO's X-band SAR satellite that complements Sentinel-1 for Indian applications — this article breaks down its imaging modes, frequency trade-offs, and where it genuinely outperforms C-band sensors for flood mapping, crop monitoring, and coastal work.

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SAR Backscatter for Soil Moisture: Sentinel-1 Methods Explained
4 Jul 20266 min

SAR Backscatter for Soil Moisture: Sentinel-1 Methods Explained

A technical walkthrough of how Sentinel-1 C-band SAR backscatter is used to estimate soil moisture across Indian agricultural land, covering the physics, key retrieval algorithms, and practical pitfalls.

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Flow Accumulation and Stream Order from DEM in QGIS: Step by Step
3 Jul 20266 min

Flow Accumulation and Stream Order from DEM in QGIS: Step by Step

A step-by-step QGIS walkthrough of flow accumulation and stream ordering from a DEM — covering sink filling, flow direction, and common mistakes that silently break watershed delineation in Indian study areas.

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Estimating Crop Yield with SAR and Optical Data Fusion in GEE
2 Jul 20267 min

Estimating Crop Yield with SAR and Optical Data Fusion in GEE

Cloud cover during India's kharif season makes optical-only yield models unreliable. This article shows how to fuse Sentinel-1 SAR and Sentinel-2 data in Google Earth Engine to build a cloud-robust crop yield estimation workflow.

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Flood Depth Estimation from Sentinel-1 SAR: Methods and Limits
1 Jul 20267 min

Flood Depth Estimation from Sentinel-1 SAR: Methods and Limits

Flood extent mapping from Sentinel-1 SAR is now routine, but translating backscatter into actual water depths is far harder. This article breaks down the main methods — hydraulic model fusion, DEM differencing, and their real limits — for Indian flood contexts.

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GRACE-FO vs GRACE: What Changed for Groundwater Monitoring
30 Jun 20266 min

GRACE-FO vs GRACE: What Changed for Groundwater Monitoring

GRACE-FO introduced laser ranging and improved accelerometers over its predecessor, but instrument upgrades and a one-year data gap create real methodological challenges for anyone building long-term groundwater depletion records over India.

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SUHI vs RUHI: Separating Surface and Air Temperature in UHI Studies
29 Jun 20267 min

SUHI vs RUHI: Separating Surface and Air Temperature in UHI Studies

SUHI measures radiative skin temperature from satellites; conventional UHI measures screen-level air temperature. Conflating the two leads to flawed mitigation policy in Indian cities where ground-truth met data is scarce.

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RTK vs PPK GNSS: Choosing the Right Mode for Drone Surveys
28 Jun 20267 min

RTK vs PPK GNSS: Choosing the Right Mode for Drone Surveys

RTK and PPK both deliver centimetre-level GNSS accuracy for drone surveys, but the right choice depends on your data link reliability, terrain, and post-processing workflow — a decision that matters especially across India's varied field conditions.

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Ground Sampling Distance Explained: How GSD Affects Map Accuracy
27 Jun 20267 min

Ground Sampling Distance Explained: How GSD Affects Map Accuracy

Ground sampling distance (GSD) sets the resolution ceiling for every drone survey output. This article explains the GSD formula, application-specific thresholds for Indian projects, and the most common field mistakes that make datasets unusable.

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Network Analysis in QGIS: Shortest Path and Service Area Tools
26 Jun 20267 min

Network Analysis in QGIS: Shortest Path and Service Area Tools

A practical guide to network analysis in QGIS covering shortest path routing and service area tools, with India-specific data preparation steps, a Nagpur worked example, and guidance on the QNEAT3 plugin for isochrone generation.

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Exporting Large GEE Results to Google Drive Without Hitting Limits
25 Jun 20266 min

Exporting Large GEE Results to Google Drive Without Hitting Limits

GEE exports silently fail at scale because of pixel count limits, file size constraints, and Drive storage quirks. This post explains spatial tiling, key export parameters, and when to switch from Drive to Cloud Storage for large-area workflows.

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Landsat Surface Temperature: Retrieving LST from Band 10 Step by Step
24 Jun 20267 min

Landsat Surface Temperature: Retrieving LST from Band 10 Step by Step

A step-by-step technical walkthrough of Landsat LST retrieval from Band 10, covering DN-to-radiance conversion, brightness temperature, NDVI-based emissivity estimation, and where calibration errors cost you several degrees Celsius.

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Sentinel-2 Atmospheric Correction: DOS vs Sen2Cor vs ACOLITE
23 Jun 20267 min

Sentinel-2 Atmospheric Correction: DOS vs Sen2Cor vs ACOLITE

Choosing the wrong atmospheric correction method can silently bias every NDVI, land cover, or water quality result you derive from Sentinel-2. This article compares DOS, Sen2Cor, and ACOLITE against the aerosol and humidity conditions typical of India and South Asia.

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Random Forest vs SVM for LULC Classification: Which Wins in GEE?
22 Jun 20266 min

Random Forest vs SVM for LULC Classification: Which Wins in GEE?

A direct comparison of Random Forest and SVM for LULC classification in Google Earth Engine, using Indian landscape challenges — class imbalance, monsoon cloud cover, and spectral confusion — to show where each algorithm actually wins.

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Mapping Reservoir Storage Changes with NDWI and Landsat in GEE
21 Jun 20266 min

Mapping Reservoir Storage Changes with NDWI and Landsat in GEE

A step-by-step guide to mapping seasonal reservoir storage changes across India using NDWI and Landsat imagery in Google Earth Engine, with honest notes on turbidity, cloud shadow, and threshold validation.

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NDVI Time-Series Analysis in GEE: Detecting Seasonal Crop Cycles
20 Jun 20267 min

NDVI Time-Series Analysis in GEE: Detecting Seasonal Crop Cycles

A technical walkthrough of building NDVI time-series workflows in Google Earth Engine to detect kharif, rabi, and zaid crop cycles across Indian agricultural landscapes, covering collection setup, cloud masking, and phenology curve extraction.

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Resourcesat-2A LISS-IV Explained: Bands, Resolution and Use Cases
19 Jun 20267 min

Resourcesat-2A LISS-IV Explained: Bands, Resolution and Use Cases

A practitioner-oriented reference explaining Resourcesat-2A LISS-IV's spectral bands, 5.8 m resolution, and how it compares to Sentinel-2 and Landsat for India-specific mapping workflows.

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SAR Coherence for Landslide Mapping: Sentinel-1 Methods Explained
18 Jun 20267 min

SAR Coherence for Landslide Mapping: Sentinel-1 Methods Explained

SAR coherence change detection lets disaster managers map monsoon landslides in the Himalayas and Western Ghats even under total cloud cover. This article walks through the full Sentinel-1 SLC processing workflow in SNAP and explains where the method succeeds and fails in Indian terrain.

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DEM Vertical Accuracy: SRTM vs ALOS vs Copernicus Compared
17 Jun 20267 min

DEM Vertical Accuracy: SRTM vs ALOS vs Copernicus Compared

A technical comparison of SRTM, ALOS AW3D30, and Copernicus DEM vertical accuracy across India's diverse terrain — with a decision framework for watershed delineation, flood mapping, and landslide modelling.

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Crop Water Stress Mapping with Sentinel-2 NDWI and NDRE in GEE
16 Jun 20266 min

Crop Water Stress Mapping with Sentinel-2 NDWI and NDRE in GEE

NDVI lags crop water stress by days that cost yield. This article shows how to map early stress across the Indo-Gangetic Plain using Sentinel-2 NDWI and NDRE in Google Earth Engine, with step-by-step GEE code.

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Optical vs SAR Flood Mapping: Choosing the Right Satellite Data
15 Jun 20267 min

Optical vs SAR Flood Mapping: Choosing the Right Satellite Data

SAR or optical imagery for flood mapping in India? This article breaks down the decision logic — cloud cover, terrain, timing, and use case — with evidence from Sentinel-1 and Sentinel-2 studies across Indian flood-prone regions.

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Detecting Saltwater Intrusion in Coastal Aquifers with Remote Sensing
14 Jun 20266 min

Detecting Saltwater Intrusion in Coastal Aquifers with Remote Sensing

A practical walkthrough of how satellite sensors, InSAR, and EMI surveys detect saltwater intrusion in India's coastal aquifers across Gujarat, Tamil Nadu, Kerala, and Odisha — and where each method's limits lie.

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Mapping Urban Heat Islands with Landsat LST in Google Earth Engine
13 Jun 20267 min

Mapping Urban Heat Islands with Landsat LST in Google Earth Engine

A practical GEE workflow for mapping urban heat islands using Landsat 8 LST in Delhi NCR, covering NDVI-based emissivity estimation, Band 10 brightness temperature conversion, and the full LST retrieval formula.

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GNSS Jamming and RTK Surveys: What Field Teams Must Know
12 Jun 20267 min

GNSS Jamming and RTK Surveys: What Field Teams Must Know

GNSS jamming and spoofing are growing threats to RTK and PPK surveys in India. This guide explains how interference breaks carrier-phase positioning and what field teams can do to detect and recover from it.

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Drone Surveys for Waste Quantification: Methods and Accuracy
11 Jun 20267 min

Drone Surveys for Waste Quantification: Methods and Accuracy

A technical walkthrough of drone photogrammetry workflows for legacy waste quantification in India, using the Bandhwari landfill survey as a case study — covering GCPs, GSD, and realistic volume accuracy.

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Watershed Delineation in QGIS Using SRTM DEM: Step by Step
10 Jun 20266 min

Watershed Delineation in QGIS Using SRTM DEM: Step by Step

A step-by-step QGIS workflow for watershed delineation using free SRTM 30 m DEM, covering sink filling, flow direction, flow accumulation, stream extraction, and pour-point snapping — with India-specific guidance on where the process commonly fails.

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Mapping Soil Salinity in GEE: Indices, Datasets and Code
9 Jun 20265 min

Mapping Soil Salinity in GEE: Indices, Datasets and Code

A practical guide to mapping soil salinity in Google Earth Engine using validated spectral indices, Sentinel-2 and Landsat datasets, and code patterns tuned for India's Indo-Gangetic Plain and coastal deltas.

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Landsat Band Combinations: Which to Use and When
8 Jun 20267 min

Landsat Band Combinations: Which to Use and When

A practical reference guide to Landsat 8 and 9 band combinations — natural color, false color, agriculture, and more — with Indian landscape contexts including the IGP, Punjab croplands, and Deccan scrub.

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Sentinel-2 Cloud Masking: SCL Band vs. s2cloudless Compared
7 Jun 20267 min

Sentinel-2 Cloud Masking: SCL Band vs. s2cloudless Compared

A technical comparison of Sentinel-2's built-in SCL band and the s2cloudless ML model for cloud masking, with a focus on Indian monsoon conditions where cloud cover disrupts agricultural monitoring and flood mapping.

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Red Edge Indices for Crop Stress Detection: Beyond NDVI
6 Jun 20266 min

Red Edge Indices for Crop Stress Detection: Beyond NDVI

Red edge indices like NDRE and CIre detect crop stress weeks before NDVI saturates — here is how to apply them on Sentinel-2 imagery for Indian wheat and rice fields.

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SAR Flood Mapping with Sentinel-1: How It Works and Why It Matters for India
6 Jun 20267 min

SAR Flood Mapping with Sentinel-1: How It Works and Why It Matters for India

SAR flood mapping with Sentinel-1 works through microwave backscatter contrast between water and land — and with India's new ISRO-Jal Shakti MOU, it is moving from research into operational policy. Here is how the technique actually works, step by step.

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How GRACE Satellites Measure Groundwater Loss Beneath Your Feet
6 Jun 20267 min

How GRACE Satellites Measure Groundwater Loss Beneath Your Feet

GRACE and GRACE-FO satellites measure tiny changes in Earth's gravitational field to track groundwater depletion from orbit — a method now central to water-resource monitoring in India and globally.

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Aerial view of lush green farmland fields in a patchwork pattern, evoking NDVI vegetation health mapping from Sentinel-2 satellite imagery
6 Jun 20266 min

Reading NDVI: turning Sentinel-2 into vegetation insight

NDVI turns red and near-infrared bands into a simple measure of how green and healthy vegetation is. Here is how I compute and read it from Sentinel-2 and Landsat in my Punjab and Delhi NCT work.

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Surveyor using a GNSS receiver on a survey tripod in an open field, illustrating ground control point measurement for accurate drone mapping
29 May 20267 min

GCPs and GNSS: how to get drone maps to line up

A practical guide to ground control points and GNSS for accurate drone maps, drawn from my UAV photogrammetry work at IIT Roorkee using Emlid Reach RS3 and Trimble DA.

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Data analytics dashboard with charts and graphs on a screen, representing zonal statistics and buffer analysis output in QGIS
21 May 20267 min

Buffer analysis and zonal statistics in QGIS, explained

A practical guide to buffer zones and zonal statistics in QGIS for measuring environmental footprint, grounded in my Delhi NCT industrial impact work with Sentinel-2 indices.

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Laptop screen displaying data and a software interface on a desk, evoking the choice between QGIS and ArcGIS Pro GIS software
13 May 20266 min

QGIS vs ArcGIS Pro: which GIS tool should you learn?

An honest practitioner comparison of QGIS and ArcGIS Pro for GIS and remote sensing work, with cost, workflow, and practical advice for students in India.

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Aerial view of a river winding past built-up land and vegetation, illustrating NDWI water mapping and NDBI built-up land mapping
5 May 20267 min

NDWI and NDBI explained: mapping water and built-up land

A plain guide to NDWI and NDBI: the formulas, band pairs, and how I read them alongside NDVI to map water, moisture, and built-up land in India.

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Flooded paddy rice field under irrigation in northern India, illustrating the water-intensive cropping that drives Punjab groundwater depletion
27 Apr 20266 min

Groundwater depletion in Punjab: what 25 years of satellite data reveal

Punjab grows much of India's grain but is draining its aquifers fast. Here is how Landsat NDVI and NDWI change maps over 2000-2025, paired with groundwater data, expose the stress.

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Satellite orbiting above Earth in space, representing the Sentinel-2 sensor and its multispectral bands
19 Apr 20266 min

Sentinel-2 bands explained: a practical beginner guide

A plain, practical guide to Sentinel-2 bands, their 10/20/60 m resolutions, and which bands to use for NDVI, NDWI, and NDBI, with free Copernicus access.

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Aerial survey drone flying over a landscape, illustrating UAV photogrammetry from flight planning to orthomosaic generation
11 Apr 20267 min

Drone photogrammetry step by step: from flight plan to orthomosaic

A field-tested guide to UAV photogrammetry, from flight planning and ground control to processing an orthomosaic, DSM, and point cloud, drawn from my survey work at IIT Roorkee.

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Student working on a laptop at a desk while studying, representing learning GIS and remote sensing to start a career in India
3 Apr 20267 min

How to start a career in GIS and remote sensing in India

A practical roadmap to break into GIS and remote sensing in India: degrees, QGIS and ArcGIS, Python, Google Earth Engine, Esri and IIRS/ISRO certifications, projects, and where to find jobs.

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View of Earth from space with glowing connected lights, evoking Google Earth Engine planetary-scale cloud processing of satellite data
26 Mar 20267 min

Google Earth Engine: cloud remote sensing for everyone

Google Earth Engine puts decades of satellite data and planetary-scale processing in your browser. Here is what it is, why it matters, and how to start.

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