GIS Blog

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Two NZs?

New Zealand often suffers from being overlooked on world maps.  At least one map has tried to reverse that trend. When it comes to world maps, NZ has a problem.  We often get forgotten!   So much so that there’s a whole section of the internet dedicated to documenting this.  One doesn’t need to look very…

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Join the Band (Combinations)

Most satellite images have multiple bands.  We can change the way an image is displayed to highlight certain features in the images. With kudos to Little Feat’s Join the Band album, we’ve been looking at satellite images a lot recently and have seen how many satellite images are composed of multiple bands, or layers.  When working with…

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The Paint-By-Number Tool

We can use remotely sensed images to extract useful information about the land surface using image classification.  The first step is usually segmentation, which groups pixels with common properties together.  This post is a quick look at what it is and how to do it. Ah, a nice, relaxing paint-by-numbers landscape for a Friday.  While I’d…

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The grass is always greener, isn’t it?

This post looks at the NDVI vegetation index that can be derived from multispectral images and give us useful information about the state of plant health for an area. We’ve been talking about satellite images recently and in this post we’ll start going over some of the beneficial information we can get from those images…

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Enhance!

In remote sensing analysis, the higher the image resolution the more valuable the asset.  In this post we cover pansharpening, the process of using high resolution panchromatic imagery to improve the resolution of coarser multispectral imagery. I’m not a big fan of all those CSI-type shows, especially when it comes to their treatment of images. …

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Wavelength(s)

Remotely sensed images are incredibly useful sources of GIS data.  In this post we begin looking at using satellite images to create useful GIS data. Without giving too much away about myself, one of my top five absolute favourite Van Morrison songs is Wavelength, from the 1978 (egads!) album of the same name.  It might…

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Deleting Smokers – Part 1

This is the first post in a series covering the development of a Python script to carry out some analysis.  We cover the idea behind the script and develop some pseudo-code used to flesh it out. For those of you having trouble sleeping, this post may be the one for you.  In several previous posts, we’ve…

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Which Way to Mecca?

Knowing the direction to Mecca is important to all Muslims.  This post goes into the best way to find it. (Updated May, 2019 to take compass variation into account.) Today is Friday and all over the world, Muslims will join together for Friday prayers, like a wave washing over the world from east to west. …

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I Can See For Miles and Miles and Miles

Viewsheds are useful layers that allow us to model visibility of features on the surface of the earth.  In this post we look at the effect of the curvature of the earth on these raster layers With due homage to The Who, this post goes out to all those who adhere to the crazy idea…

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Paths to Good GIS: Default Workspaces

Setting default workspaces is a good data management habit to get into – it may save you lots of heartache when saving new layers. There are lots of things that contribute to doing good GIS work, and practicing good file management has to be near the top.  Anyone who has done any amount of GIS…

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