18 February 2011

Dummies Guide to Search for Satellite Images

Is there an image for my study area?, what is the resolution?, how much does it cost?. We have all heard these questions. To answer these questions is not as straightforward as one thinks. There are numerous satellites, various data providers/sources, and there are numerous considerations like costs, copyrights, and quality. So a systematic approach to data search and acquisition is the first step to using satellite sensor data in your project.

In order to facilitate this,
IWMI's Data Storehouse Pathway team Prepared this guide book. This is by no means a comprehensive document to search for images. There are numerous other satellite, sensors, and possibilities. However, definitely this document will meet the need of most satellite sensor data users.

Where do you begin ?
Your first task is to get a precise bounding (e.g., upper left and lower right latitude and longitude) coordinates of your study area. Then, first and foremost check IWMIDSP (
http://www.iwmidsp.org) for available images. If not, most satellites have boxes (path/row) drawn on map that you can just show your area. However, if you are getting very high resolution images you better have precise coordinates of your study area, since you will have to pay per square kilometers.

How do you look for image(s) you want ?
First, ask your self what is your main objective. Based on this look for “ideal” image(s) that helps in your study objectives. Decide to purchase images based on what is feasible financially. However, the good news is that there is now enormous amount of free satellite images for any part of the world.

What types of satellite images suite your interest ?
All satellite images can be roughly categorized into following categories (and you can choose them based on factors such as your project objectives, resources available for processing, expertise available for interpretation, and costs). We almost exclusively consider optical (or passive) sensors in section 4.1 to 4.3. In section 5.0 we will touch upon hyper spectral sensors and in section 6.0 we will discuss active sensors (the link to the complete documentation below).

Coarse resolution (100 m and up)
There is a treasure of high quality science data from coarse resolution sensors. These are “spatially” coarse (pixel size 100 m, 250m, 500m, 1000 m, and 10000 m), but are rich in spectral, temporal, and radiometric resolutions.

Below, a screen-grab of a easy navigable windows explorer style Dummies Guide hosted at Data Storehouse Pathway FREE data portal.

OK, now click HERE to access the “Dummies Guide to Search for Satellite Images” full documentation.

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