Using satellite images: a practical guide

Using satellite images: a practical guide


Satellite images are like maps: they are full of useful and valuable information, provided you select them carefully, with specifications in line with your application. GIM offers a variety of very high, high and medium resolution imagery and more important, gives you the necessary support.

How to select the most appropriate imagery: 5 tips and strategies 

Satellite images can show you how much a city has changed, where informal settlements are located, how much bushes have to be cleared along your infrastructure, how well your crops are growing, or where to locate your transmission towers.

To benefit from the rich information in a satellite image, you need to consider and combine the following 5 elements and we will help you providing the appropriate answers.

Define the scale

What is the size and shape of my area of interest? What level of detail is required for my application?

The higher the resolution, the smaller the image footprint. Satellites are scanning the Earth collecting image strips of a given width. Some systems are designed to quickly collect large areas with a certain level of detail (e.g. 1,5 m resolution with a 60 km swath width) while others are more suited to zoom into smaller areas (e.g. 30 cm resolution with a 13 km swath width).

So it is key to first look at the smallest landscape features you want to distinguish in the image and at the area you need to cover. Combining these two elements we will determine the most suited resolution and shorten the list of possible satellites also taking into account minimum order size and satellite agility.

Define the time

Do you need very fresh imagery or can we go back in time and if so how long? Are you interested in a specific time period or season? Do you have timing constraints for your project? Does your application require several images of the same place (i.e. monitoring)?

We have access to many catalogues and are able to go way back in time, right back to the Seventies. So we can search and find the best images for any time period. We are also able to task satellites and get fresh information on demand. In this case we first conduct a feasibility study to determine the required collection time and the chance of succeeding. Finally, repeats are also possible and hence analysing changes in the landscape.

Define the information

Do you need to assess the health of your crop or to discriminate various geological structures? Are you interested in seeing your area in 3D?

The sensors on board satellites are capable of measuring the radiation reflected or emitted by the Earth’s surface or objects on the ground. This information enables you to analyze satellite images in-depth and to interpret them correctly. For this, GIM offers countless types of spectral images: panchromatic (gray values), red/green/blue, near-infrared, yellow, red-edge, short-wave infrared, thermal infrared, X/L/C radar, etc.

Optical and radar satellites can also collect elevation information. Different techniques are used to derive digital terrain models providing the topography of your area or surface models showing features such as buildings or trees in 3D.

Define the budget

Together with the other constraints, the available budget will determine the sensors and imagery types you can afford. So no need to consider options that you cannot afford. We will accommodate your constraints and suggest the best possible option.

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