Are you interested in utilizing satellite imaging in your next project but not sure what kind of imagery you need? You’re in the right place!
Why use satellite imagery
You’ve probably seen satellite imagery of hurricanes from the National Hurricane Center or used directions from Google Maps. These applications leverage data from satellites hurling 500+ kilometers above the earth. There are over 2,500 active satellites in the sky, equipped with varying combinations of hardware to generate different data & insights. Many satellites capture more data than just the visual spectrum of light and can see far beyond what the eye could see.
But which satellite & sensor combination is the most ideal for my project? How do I get that data, and how much does it cost? Through this article, users will be able to learn the basics of remote sensing and the common ways that companies leverage this data.
Remote sensing 101: Feeling without touching
Remote sensing provides users with a way to view an area without having to specifically visit that area. This is done by sensing and recording reflected energy from the surface and processing, analyzing gathered information.
There are two kinds of remote sensing: passive remote sensing, and active remote sensing.
Passive Remote Sensing – the satellite detects when naturally occurring energy is available, thus producing natural color, multispectral, and/or hyperspectral images.
Active Remote Sensing – active sensor satellites provide their energy source for illumination to record imagery. Active satellite sensors emit radiation such as microwaves which are reflected off the ground and back to the satellite sensor. The advantage of using an active sensor is the ability to obtain measurements regardless of the time of the day. The most common type of active sensor for satellite imagery is synthetic aperture radar (SAR). This type of sensor can provide useful data during times of heavy cloud cover.
As you can see from the above image of Canberra, Australia, passive satellite imagery (left) tends to produce an image that looks similar to one observed by the naked eye. By comparison, the SAR imagery looks less natural. Both types of imagery have different purposes. Google Maps leverage passive satellite imagery to produce their beautiful maps. Emergency response crews leverage SAR imagery to pierce through cloud cover immediately following hurricanes & volcano eruptions.
What is spatial resolution and how much do I need?
Spatial resolution refers to the size of one pixel and describes how much detail in a satellite image is visible to the human eye.
Proimagery offers satellite images with varying resolutions from 3-meter medium resolution satellite imagery up to sub-meter high-resolution satellite images. Choosing the resolution of images may come down to how large your project area might be and how important ground features need to be observed and analyzed.
To help you know the difference between various resolutions of satellite images data, look at these two satellite images captured over Woden Valley, Australia. The left image is a 70cm high-resolution satellite image from Kompsat-3. At this spatial resolution, you can easily see buildings, roads, property boundaries, and even features like swimming pools. The image on the right is a medium resolution Dove satellite imagery which provides a much coarser view and detail of the ground features.
Comparison between the details of high resolution and medium resolution satellite imagery
Generally speaking, areas smaller than 25 square kilometers benefit from the detail from high-resolution satellite imagery. Areas greater than 100 square kilometers benefit from cost savings of using medium resolution satellite imagery without losing much detail. And areas between 25 and 100 square kilometers are likely case-specific. If you’re curious as to what spatial resolution you need, reach out to us and we can provide some guidance.
How can I utilize multispectral imagery?
Most commercial satellites are capable of imaging beyond the visible light spectrum and come equipped with sensors that can view four spectral bands of imagery (blue, green, red, and near-infrared bands). With the use of multispectral imagery, users can extract various information not visible to the human eye since multispectral bands can be used to identify various characteristics of ground features such as vegetation, water extent, soil moisture, roads, etc. which have different spectral signatures.
Here are some common uses of multispectral imageries Proimagery can provide to users:
Using vegetation index on assessing vegetative analysis and monitoring crop health using time-series analysis from planting to harvesting
Extracting flood extent using Normalized Difference Water index.
If you’re still not sure what kind of imagery you need to buy for your project, we can help! Set up a meeting with us and we’ll help you get an idea of the exact type of imagery you need for your project, along with a detailed pricing estimate.