The biggest benefit and challenge of remote sensing is the massive amount of data available. With Radiant.Earth, you can sort through material using filters. In this article, you will learn how to filter images.
First, you'll need to open a new project (check out this tutorial), and zoom into the area you want to search.
There are several different criteria that you can use to sort through data, including location, date, cloud cover, sun elevation, sun azimuth, ingest status, imagery sources, and owner.
When starting a new project, you will automatically see images pop up. If you're in an old project, click
Generally, you'll want to look at geography first. After zooming in to zoom level 8 (see the top right corner), Radiant.Earth will show you all scenes that fall within the view screen. If you want to view a specific scene area, you can do this by either drawing the shape of the area where you want to look, using a shape you already drew, or importing a zipped shapefile to use as the area of interest.
You're also able to search for a location on the map by clicking the magnifying glass in the top right corner. You can enter a place name, or coordinates in decimal form (with negatives [ - ] for West and South rather than the letters E/W and N/S, with 38.895590, -77.024813 representing DC, 38 degrees North and 77 degrees South).
Sort/Filter, and scroll down to "Area of Interest." Click
Select an area and either click on an existing shape, or click draw shape. Click
Start Drawing and click on the map to make the first point of your shape. Keep clicking to make points, and click the first point to close the shape. Click
Stop Drawing when you're finished, and the imagery will automatically filter to include only scenes within that shape.
You can also click
Import Shape and import any zipped Shapefile. Any imagery that overlaps with the Shapefile (whether point, line, or polygon) will appear in the filter options.
To search for images based on what date they were taken, click
Set Date Filter .
You can either choose one of the presets (images from "Today," "The Last Month" [date of today from the same date from the previous month], "The Last Year" [date of today from the same date the previous year]) or select manually, either typing the dates in or clicking the start date followed by the end date.
One of the biggest obstacles to remote sensing is the presence of cloud cover. While some light haze can be corrected, clouds can completely obstruct the view of the ground, rendering the scene useless.
Remote sensing scenes are often graded by how much of the image is obstructed. This is sometimes done automatically and sometimes done manually. How much cloud cover you are willing to deal with depends on your needs. Since some scenes are large, it's possible that a heavily clouded image may have the area that you are interested in uncovered.
Generally, if you want larger areas, you'll need lower cloud cover; if you need specific dates, you might have to compromise with some cloud cover. By default, you'll get images with 0% to 10% cloud cover. Use the sliding scale to adjust.
Sun Elevation and Azimuth
The brightness of an image will be affected by the direction that the sun is hitting the Earth. Sun Elevation refers to the angle of the sun above the surface of the earth. Sun Azimuth refers to the angle of the sun from due north. Both are affected by time of day, time of year, and latitude.
While most remote sensing satellites take images of the earth at approximately the same time every day, where the sun is in the sky at that time varies. Imagine facing due east at 10 am in the northern hemisphere (Washington, D.C. in particular). At the equinoxes, the sun will appear about 30 degrees above the equator and 30 degrees to your right. As the earth tilts, where the sun is will change. At the same time and same place at the winter solstice, the sun will appear only 20 degrees above the equator and nearly 60 degrees to your right (that's why it feels like the sun is rising and setting for most of the day in the winter).
For most uses, your choice of elevation and azimuth will be dictated by when and where the image you want to use was taken, so you should keep the default settings. However, you may want to compare two different times and places. In that case, you'll want similar azimuth and elevation so that the error from these values is minimized.
Note that you will only be able to search by these values if that metadata is included.
Radiant.Earth uses images from cloud-based servers, bringing them into dedicated servers for your use. This process is called ingestion. Once a scene has been ingested, it becomes available for display at all times; a scene that was ingested for someone else (and is available for everyone) will appear as ingested for you.
Selecting by ingest status will allow you to save time by only picking images that are already in the system or that are not already in the system. Scenes will be ingested when you add them to a project.
Radiant.Earth provides imagery from several different satellites and sources.
You can select any of the available and compatible sources, so that you can pick, for example, only high quality Planet data or the mid-resolution Landsat data, especially if you want to compare images from the same sensors.
You can also select by who owns the data. Under "All users" you will find data that is freely available through Radiant.Earth. Under "My imports" you will find data that you have personally imported.
Once you have narrowed down the options, you can add data in a few ways. You can click the
+ sign to select all narrowed-down options, or select each option individually. Then, click
Add Scenes . Your imagery will be ingested or loaded directly into your project.