Land Sense - Remote Sensing in Surety Pro

Modified on 2017/09/18 19:22 by Adam — Categorized as: Uncategorized

Land Sense^TM represents remote sensed imagery data, tools and services provided by AgriData, Inc. It is accessed through the Surety^® Pro version of the mapping software.

Accessing Land Sense in Surety® Pro¶

After creating or selecting a Client in Surety® Pro, select or draw a field or area of interest. You will then access the Land Sense™ interface by clicking the Land Sense™ link on the right panel. This will launch the Land Sense™ imagery manager for the selected field/area.

Land Sense imagery¶

Sentinel 2A & B satellite data is currently the only imagery dataset available. For more information on the Sentinel 2 product, view the “Sentinel 2 Technical Guide” and the “Introduction to Remote Sensing Guide”.

Part 1 – Land Sense imagery manager Interface¶

In the upper left corner, just below the header, Area of Interest will be shown in the blue tile. It currently lists the Client, Farm and year or just Client and year if no Farm is selected.

The imagery manager page will contain a tile for each image available for a given area of interest and within search criteria, such as date range or source. Currently the date range is set from January 1, 2017 to the current date. Each tile represents an image date, source, and cloud cover percentage as well as an area to view thumbnails of derived products which you can choose from at the bottom of the tile.

Date and time: This date and time represent when the image data was acquired by the source. It is based on the center of the scene/image acquisition. See also Appendix B: FAQ-Q2

Source: This will represent the data source, such as the Sentinel satellite or acquisition company name, etc.

Cloud cover (if available): This represents a percentage of cloud cover across the whole scene/image, not the area of interest. Please refer to the true color (RGB) image for cloud occurrences within an area of interest. Add the RGB image to the map interface to see a larger representation of the area of interest. Do not use derived image algorithms, such as NDVI, when clouds or shadows may be present in the area of interest.
Also see Appendix B: FAQ-Q3 and “Introduction to Remote Sensing Guide”

Thumbnails: This area will show a thumbnail for the derived product selected at the bottom of the tile. (after product is selected)

Derived Products: Available derived products will be listed here for selection. When selected, a thumbnail will be generated. Also see Appendix A: available derived products.

See also Appendix B: FAQ-Q2

Part 2 - Creating Derived Products¶

To create a derived product listed on the image tile, click one of the derived product icons at the bottom of the tile. The product will have been created when a thumbnail of the derived product appears in the tile.

For explanation of derived products see Appendix A, or download the “Introduction to Remote Sensing Guide”.

The first time you attempt to create a derived product for a given image tile, Land Sense™ will check to see if the image is “local” or needs to be downloaded. If the image is ”local”, it will create the derived product thumbnail within seconds. If the imagery data needs to be downloaded it will begin the download process. Depending on internet speed and size of the product this may take sometimes several minutes to achieve.

Task Progress Bar – The blue progress bar located at the top of the page below the header will show the progress of the task selected. For example, when a derived product is chosen for a given image date and that image has not been downloaded “locally”, the progress bar will represent the progress of the download in blue color and will completely fill the area when the task is completed.

Once the image is “local” it will remain there for some time and any area of interest that falls within that image area will access it as a “local” image.

You can switch between derived product thumbnails by clicking another product icon.

Part 3: Adding derived products to the map interface¶

Derived images created in the imagery manager can be added to the main map interface. These new layers will be accessible through the Land Sense™ layer name under the Layers tab.

Once the derived image thumbnail has been created for the desired date, you may add the image to the map interface by left-clicking the small + sign in the upper right corner of the image tile. The process bar will show when it has been added and the + sign will change to a small trash can icon. You can continue to add more derived images to the map interface this way.

Part 4: Controlling and viewing Land Sense™ images on the mapping interface¶

Once a derived product has been added to the mapping interface it is accessed and controlled as a Layer under Boundaries called Land Sense™. Clicking the small + sign next to the Land Sense™ layer will expand the Land Sense layers and list all imagery available to view on the map interface for the displayed map region.

By clicking the checkbox next to the image product desired, the image will be displayed on the map interface. See Appendix B: FAQ-Q4

There are three additional controls for each listed product and are represented by icons to the right of the product identifier.

Trash Can icon – the small trash can icon allows the user to delete the associated image product from the Land Sense™ layer and mapping interface.

Spyglass – the spyglass allows the user to zoom to associated image product.

Pencil – the small pencil icon returns the user to the Land Sense™ image manager.

Appendix A: available derived products¶

NDVI - The most widely used, and a basis for many other vegetation indices, is the Normalized Difference Vegetation Index, or NDVI. It works with the relationship between the NIR reflectance and visible red reflectance values to gives us an index related to relative biomass.

NDVI=(NIR−Red)/(NIR+Red)

NDVI comparison between healthy and unhealthy plant

Healthy Plant vs Unhealthy Plant

(0.50−0.08)/(0.50+0.08) = 0.72 (0.35−0.25)/(0.35+0.25) = 0.17

This index gives a value between -1 and 1, with most biomass readings in the 0.1 – 0.9 range and the higher value representing a higher relative biomass.

RGB - Resembling that of a picture taken with a handheld camera or a smartphone, true color imagery is a combination of the three visible spectral bands, Red, Green, and Blue or RGB. These images are used for base maps, feature recognition, boundary and other feature drawings or whenever ground features are to be recognized by their actual color.

Appendix B: FAQ (frequently asked questions)¶

Q1: Why is there sometimes more than one tile for a given image date and source?

A1: Depending on the source there can be overlap between image scenes taken at the same time and depending on the area of interest’s location and size, there could be up to four image scenes available. In most cases they represent the same acquisition time period but can have different cloud percentages because the cloud percentages are based on the individual image scene and not the acquisition strip.

Q2: It shows an image date on the tile but the true color (RGB) is all black or NDVI, EVI etc. is all one solid color?

A2: This is a result of the area of interest falling outside the acquisition path of a satellite. The area of interest is located within the imagery area but due to the angle that the satellite flies, the area of interest lies in a null area or area with no data.

Q3: What does the cloud percentage represent for each image?

A3: This cloud percentage estimation, and remember, it is an estimation, is based on the cloud cover across the whole scene. Depending on the source, a whole scene may represent an area that covers hundreds and even thousands of square miles, so always check the true or false colored images to see if your area of interest has cloud cover or cloud shadows. Do not use derived image algorithms, such as NDVI, when clouds or shadows may be present in the area of interest.

Q4: Why does the number of Land Sense™ products available change as I zoom in and out, regardless of the field selected?

A4: Surety® Pro uses a geospatial search to display the Land Sense™ layers, which means that it will display imagery that is in the map view, for the given Client selected, regardless if a field is selected. To narrow the image products available to display, zoom in on the area of interest.