The "INPUT" part of the toolbox is where you can find and select data sources. You then choose options to filter out only the data that you need.
These are the options available within the INPUT part of the toolbox. Note that they are categorised into INSERT DATASET, FILTER and COLLATE.
Instructions for using the INPUT blocks
To use one of the INPUT blocks just drag them into the workspace. The Insert New Dataset is a container block that holds other blocks. All of the other INPUT blocks are placed inside a container. Note that not all INPUT blocks will work with every block. For example, there is no need to use a Mask Out Clouds block on radar data, as there are no clouds in radar imagery.
The following sections describe how to use each of the available blocks.
TABLE OF CONTENTS
- INSERT DATASET
- PICK AREA & DATES
Use This Dataset
- As a container block, this will become a stand-alone workflow when it has a collection of appropriate sub-blocks within it.
- Use the drop-down to choose a dataset to use within this workflow.
- You can use the search icon to find datasets based on keywords or to get a full description of the drop-down dataset options.
- You will need to select an area of interest and a date range using the appropriate blocks, otherwise, this block will try to process the entire dataset.
- Use the "Save Data for Re-use" OUTPUT block at the end of the workflow to make the results available in other workflows.
- You can run this workflow independently of other workflows within the workspace by clicking on the run button at the bottom of this block.
Reuse this Saved Dataset
- If you have saved data within another workflow use this block to re-use it in another container block.
- You will need to use this block in several of the ANALYSE container blocks to bring in data that you have prepared within a separate workflow.
PICK AREA & DATES
Select Area of Interest
- Area of Interest (AOI) is the term used to describe the physical dimensions of the area you wish to analyse. They are described using a polygon to define the geographic area.
- AOIs are created using the map interface. These could be areas you drew by hand on the map or areas you have uploaded (as shapefiles, for example).
- This block then allows you to choose a specific AOI from a dropdown menu that will show you all the areas defined on the map. This dropdown menu is dynamic, so automatically updates when you modify areas on the map.
- The analysis will then be limited to just the area you select in this block.
Select Time Period and Limit Dates To
- There are two ways to limit the time period over which the analysis is conducted.
- The first is to use the Select Time Period block.
- The second is to use the Limit Dates To.
- Select Time Period
- Choose the start and end date from the date picker.
- The analysis will be conducted over this time period
- Limit Dates To
- Use this block to constrain the analysis to certain periods of time within each year.
- You can constrain to specific months, to specific days of the year, or to specific days of the month.
- These blocks can be combined so that, for example, you only look at January and June, and you only consider the first 14 days in each of those months. The analysis will then be conducted over period defined by the Select Time Period, but only the first half of each January and each June will be analysed.
- For optical/visible sensors only.
- The default removes all image scenes that have more than the specified % cloud cover before using metrics within the data to remove clouds. This speeds up processing by removing any scenes that have too much cloud.
- Custom options will take longer to process. If you choose to apply custom criteria it will work faster if you first filter for cloud cover using the Filter With Attribute block.
- See the article on how to Create a cloud-free image of your area of interest for more guidance.
- For radar sensors only.
- Since radars can see in the dark, they collect data on both the Northward (ascending) and Southward (descending) parts of their orbit. (Whereas optical/visible sensors require sunlight, so can only collect images on one side of the orbit).
- If this block is not used, the default is to use both ascending and descending data.
Filter With Attribute
- This is a generic filter block that allows you to filter for any of the data attributes for which there is not a specific block.
Create Image Mask
- Remove all pixels from an image that are above or below a user-defined value.
- Removed pixels are transparent in the displayed map layer.
- This block can also reference saved data layers from other workflows. For example, if you have a Sentinel 1 container block, you might mask this data based on elevation data from another workflow.
- You can use as many Create Image Mask blocks as you need. The resulting logic of multiple Create Image Mask blocks is to create an "AND" logic across multiple datasets. That is, you can display only those pixels in a dataset where several criteria are simultaneously met.
- If you only want to look at a subset of available bands in the data, use this block to select them.
- This can speed up analysis as a smaller number of data layers need to be processed.
- The block is dynamic so will change depending on what dataset is chosen.
Collate Images in Time
- This block aggregates multiple image scenes together.
- You can select the time period over which the aggregation occurs.
- Selecting "Over entire time period" will result in only one image. Every other selection will aggregate the dataset scenes into those time periods within the time period selected.
- The choices are by year, month, week, day, hour, and minute, but for each of these, you can specify the interval. For example, you can choose "week" as the period to aggregate, but "2" as the interval. The result is an aggregate for every fortnight. Likewise, "month" and "3" will give you every quarter.
- Using the drop-down menu you can decide how to aggregate each set of data. These are:
- Median or mean, as standard arithmetic averages.
- Sum: the numeric sum (for instance, for collating occurrence data).
- Min and Max are the arithmetic minimum and maximum values.
- Greenest Pixel will ask you which band to apply it to. This is essentially finding the maximum value of one single band (and not necessarily the green band).
- Maximum Index is similar but is used when there is an index block prior to the composite.
- Count: adds up the non-zero pixels.
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