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Notes on maps, data, and decisions.
Plain-language guides to GIS methods, written for planners, developers, and anyone who has to make a decision about a place.
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Remote sensing
Spectral indices cheat sheet: NDVI, NDWI, NBR and more
The eight remote sensing indices you'll meet most, with formulas and the exact satellite bands for each.
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What is NDBI? Mapping built-up land
How satellites spot roofs and roads, and why NDBI works best alongside other indices.
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Normalized Burn Ratio (NBR): mapping wildfire burn severity
How before-and-after satellite images measure how badly land burned, and how to read dNBR.
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What is NDWI? Mapping water from space
How satellites pick out water, why "NDWI" can mean two different things, and when to use MNDWI instead.
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What is NDVI? Measuring vegetation from space
How satellites measure plant health with two bands of light, and how to read the numbers.
Read the article →Maps explained
How to read a map scale
What 1:24,000 means, why "large scale" sounds backwards, and how to measure a distance on any map.
Read the article →GIS basics
Latitude, longitude and UTM explained
Decimal degrees, degrees-minutes-seconds and UTM, and how to avoid the mistakes that put points in the wrong place.
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Raster vs vector data: what's the difference?
The two ways GIS stores the world, what each is good at, and how to choose.
Read the article →Maps explained
What is a slope map?
How steep is the land, and why does it matter? A plain guide to slope, percent versus degrees, and reading a slope map.
Read the article →GIS methods
What is suitability analysis?
How GIS ranks every location against the things that matter to a project, with a worked example and common mistakes.
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