Basic Processing of Radarsat-1 data in Snap ESA

Introduction

On April 1st, 2019. NRCAN released 35000 Radarsat-1 scenes for open-access, with anticipation of releasing more in the future. This allows anyone to access SAR scenes covering Canada as far back as 1995 for free! This is incredible progress, however, very little documentation exists on Radarsat-1 file conventions or processing steps to create a usable product. This tutorial looks to fill this gap; provides users with basic background on Radarsat-1 and its file conventions, along with instructions on downloading Radarsat-1 scenes, and basic processing techniques within open-source SNAP ESA software.

Retrieving a Radarsat-1 Product

EODMS Account

Before we begin working in SNAP, we first have to download a Radarsat-1 product from NRCAN. We begin at the Earth Observation Data Management System. A main screen as per Figure 1 should greet you. In order to download products, an account must first be created. This can be done by clicking on the Register (Required to Order) link under the Users subsection on the left-hand side of the page. Follow the on-screen instructions to create your account, confirm your email, and change your password.

If you already have an account, log into EODMS by clicking on the Login link under the Users subsection on the left-hand side of the page.

Finding a Scene

Once an account is created, we can begin searching for a scene. Begin by clicking the Search under the Getting Started subsection on the left-hand side. What will appear are a series of grey boxes indicating the steps needed to locate and download our scene. Each numbered step below corresponds to the like numbered grey box.

1. The first step is to select our area of interest. This can be done is numerous ways, as indicated by the eight different drop-down menu's under this step. For this example, Draw an Area will be used. Information on the use of each tool available to select an area of interest can be found by selecting the ? beside each drop-down.

A. Begin by using the map on the right half of the screen to zoom into an area of interest, for this example I will be focusing the the overseas French territories of Saint Pierre and Miquelon located off the coast of Newfoundland.

B. Select the Draw and Area drop-down menu and then the Rectangle option. Draw the rectangle around an area that you wish to be included in your scene. See Figure 2 for an example.

2. Once an area of interest is selected, our date range must be selected. Select the Date Range option and input dates between which you wish to find a scene. For this example, I am searching between June 1st and July 1st 2003.

3. Now, we must select which type of data we are looking for. Select ONLY the RADARSAT-1 Open Data Products check-box, this can be found under the Radar Satellites Subsection.

4. The next step is to select specific options we wish our data to have. This includes a certain incidence angle range, beam modes, pass direction and so on. This is optional as it is dependent on the specific needs of the user. For this example, we will not modify this page.

5. Once the other steps are completed, select the Search button. If results are found, a new Results tab will open showing all matching results. If no results are found, refine your search dates and/or search area until results are found.

Downloading the Scene

The Results will list all scenes that match your search criteria, and will look similar to Figure 3. Hover over each result to highlight its footprint on the map. Select a scene you wish to work with and check the Order box. A window as per Figure 4 will appear. Check the box under the Select item(s) tab and then the Update Cart button. This will close the window and open a forth tab titled Cart. In this tab you will see your scene listed. Click the Submit Satellite Product Order button. This will open a tab asking for the Order Priority and Delivery Destination(s). Leave both of these as their defaults and click the Order button.

Once submitted, an email will be sent confirming your order, along with a notice that another email will sent once the scene is ready for order. This second email could take some time to arrive depending on the amount of traffic on EODMS when your order is sent in. Once this email arrives, select the HTTPS link within the email, this will open a tab in your internet browser. In this tab, click the link beside the file icon, followed by the link ending in .zip to download your scene. Save it to a place that is easily accessible later